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INŻYNIERIA MATERIAŁOWA

Dwumiesięcznik ISSN 0208-6247, e-ISSN 2449-9889 - rok powstania: 1980
Czasopismo Federacji Stowarzyszeń Naukowo-Technicznych NOT (FSNT NOT)

Structural investigation of Mg-3Ca, Mg-3Zn-1Ca and Mg-3Zn-3Ca as cast alloys

KATARZYNA KUBOK LIDIA LITYŃSKA-DOBRZYŃSKA JOANNA WOJEWODA-BUDKA ANNA GÓRAL

Magnesium alloys made of Mg-Zn-Ca system are interesting, because of possible application as bioresorbable cardiovascular stents or orthopaedic implants [1÷3]. During the last ten years, rapid growth of research in the application of magnesium and its alloys as biomaterials has been observed [4÷6]. Usage of magnesium based bone implants instead of those made of titanium or steel allows to avoid the removal surgery. Mg is the lightest of all structural metals with density close to those typical for cortical bone (1.75÷2.1 g/cm3). Other material parameters, like Young’s modulus (~45 GPa) are also similar [3]. Moreover, Mg is considered as biocompatible and non-toxic material and has been shown to increase the rate of new bone formation - it is an important ion in the formation of the biological apatites [3]. It was reported that the adult person normally consumes about 300÷400 mg of magnesium every day and an excess of Mg2+ is excreted through the urine [7, 8]. Magnesium is a cofactor for many enzymes and stabilized the structures of DNA and RNA [7, 8]. It is worth noticing that calcium and zinc are also recognized as biocompatible elements [1, 9]. A lot of studies have been performed on rare elements or/and Al containing alloys [10, 11], but these additions increase the cost of possible implant, and biocompatibility of RE is doubtful. An addition of Al can influence human nerves and induces Alzheimer disease [12]. From the metallurgical point of view, alloys made of Mg-Zn-Ca system can undergo solid-solution hardening and Ca is believed to be an effective grain refiner [13÷15]. In spite of possible benefits from magnesium based bone implants, there are a few important questions, which remain open up to date. There are problems with precise control of corrosion rate, which is usually very rapid and connected with hydrogen evolution. Rapid release of H2 in a high amount may cause inflammation process or even death [16]. Thu [...]

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INNE PUBLIKACJE W TYM ZESZYCIE

A study on superplastic forming of multiple sheet with integral stiffeners

HO-SUNG LEE JONG-HOON YOON JOON-TAE YOO JI-UNG CHOI

It is well known that blow molding process is one of the common manufacturing processes in plastic and glass industry. With the invention of the coextrusion blow molding, plastic fuel tanks are now environmentally preferable to the steel tank system in the automotive industry. A similar version of this technology in manufacturing of aircraft component is known as the superplastic forming process. Superplasticity is the ability of polycrystalline material to extend plastically to large strains when deformed in certain conditions. At appropriate superplastic conditions some fine-grained ceramics and metals have exhibited tensile elongation from several hundred to several thousand percent, while most crystalline solids can elongate by, at most, three or four percent without breaking. Even though superplasticity can be obtained in some materials by phase transformation cycling, most commercially important superplastic materials exhibit “micrograin superplasticity". This kind of superplasticity involves microstructural stability of materials during deformation. A stable, fine and equiaxed grain size is essential for micrograin superplasticity. The microstructural requirements for micrograin superplasticity are 1. a fine and equiaxed grain size, usually less than 10 microns, 2. multiple phases or quasi single phase with fine precipitates to suppress grain growth and 3. high angle grain boundaries that are mobile. In order to maintain this stable microstructure during elevated temperature deformation, multiphase alloys like eutectic or eutectoid alloys with equal portions of both phases and quasisingle phase alloy with fine precipitates to inhibit grain growth during static or dynamic recrystallization have been known as adequate superplastic alloys. The strength of the secondary phase should be similar to or lower than that of the matrix, since cavities may nucleate preferentially at the interphase boundari więcej »

Application of image analysis to porosity investigation into sintered copperalloying AISI 410L stainless steels

ANETA SZEWCZYK-NYKIEL JAN KAZIOR

It is known that stainless steels are one of the most important group of materials. Their importance is confirmed by the range of applications - products made of stainless steels. Currently steady growth of demand for stainless steels can be noticed [1], also for produced by powder metallurgy technology. Nowadays there are hundreds grades of commercially available stainless steels [2]. Many of them can be manufactured by using conventional water atomization powder and press and sinter processes. Powder metallurgy provides considerable opportunities to obtain a wide range of properties and corrosion resistance in sintered stainless steels. There are a lot of applications which required the stainless steels with high strength and good corrosion resistance. In the case of high strength and hardness requirements, graphite addition can be introduced to AISI 410L or more highly alloyed materials, such as precipitation hardening stainless steel, where 17-4 PH grade can be applied. The use of increased levels of alloying elements in sintered stainless steels (produced by powder metallurgy) is both costly and counter-productive due to the negative effect on compressibility. Graphite is added to ferritic grade of steel to promote formation of martensite. Usage of graphite addition into AISI 410L powder increases the strength and hardness of sintered steel. Beside, AISI 410L powder with graphite addition has high compressibility, so the sintered density of this material is also high and properties are satisfactory. But, on the other hand, graphite addition requires strict control of atmosphere in sintering furnace in order to achieve consistent carbon levels. Disadvantage of graphite usage is also its negative influence on corrosion resistant of stainless steels [2÷5]. In this case, introduction of copper to the AISI 410L stainless steel is an alternative solution. Copper increases corrosion resistance, while providing solid solution st więcej »

Averaged Voronoi polyhedron in the peritectic transformation modelling

ANDRIY BURBELKO JACEK POCZĄTEK DANIEL GURGUL PAULINA MALATYŃSKA MAREK WRÓBEL

Peritectic solidification of the alloys is in the centre of attention of researchers. This is a mechanism of the structure formation for many technical alloys. Peritectic solidification is believed to be the major cause of crack formation during the solidification of many steels [1]. During the peritectic solidification primary solid phase vanishes simultaneously along with liquid phase and new secondary (peritectic) phase grows as a solidification product. In the carbon steel γ-phase (austenite) appears, replacing δ-phase (ferrite) and liquid. Two separate mechanisms of peritectic solidification are known as: - peritectic reaction: when dissolution of primary phase, directly in liquid phase, is possible independently from the secondary one [2], - peritectic transformation: when primary phase is completely separated from liquid by the layer of secondary phase [3]. An analytical model of the kinetics of peritectic transformation, based on the linearized concentration gradient of the solute, has been presented by Das et al. [4]. The results shown in this paper exhibit a good agreement with the experimental results, but the difference between rates obtained by the computer modelling and relevant experimental data increase at the later stages of transformation. According to authors of [4] one of the reasons of this disagreement is the deviation from the idealized geometry. The idealized geometry of the elementary peritectic cell is usually used in the known numerical models. Furthermore, the idealized initial concentration profile of the solute in the preperitectic phase is assumed. Spherically symmetrical cell of radius (3/4n)1/3 was applied in [5], where n is the number of peritectic cells per unit volume. In the Ref. [6] only a plane spatial segment of the melt pool was used as the simulation domain. According to the analysis of diffusion transformations presented in [7], a single common mathematical model allows fo więcej »

Boost-diffusion vacuum nitriding of X37CrMoV51 steel

BARTŁOMIEJ JANUSZEWICZ PIOTR KULA EMILIA WOŁOWIEC ROBERT PIETRASIK ADAM RZEPKOWSKI

Tools for machining and dies for forging, forming and die casting require several subsequent operations of advanced vacuum heat treatment and surface engineering, namely, quenching, tempering, nitriding and PVD coating. The ability to carry out some of these operations in the same device would make the manufacturing much easier and cheaper. There have been several reports about attempts at coupling the ion nitriding and PVD plating in the same vacuum chamber [1÷4]. Modern multipurpose vacuum furnaces are able to integrate austenizing, high pressure gas quenching, single or multiple tempering and also low pressure nitriding [5÷8]. However, a reliable low pressure nitriding requires the development of models and technology for a variety of alloying tool steels due to high microstructure demands from nitrided cases on tools. The "boost-diffusion" process has been proposed to control and monitor low pressure nitriding of tools in multipurpose vacuum furnaces. The basic assumptions for this model are: 1. all "boost" stages are carried out at the constant total pressure of 26 hPa, at the ammonia supplying flow that is proportional to the total area of nitrided charge. The level of pressure is in conformity with the industrial safety requirement. This assumption should guarantee the constant and repeatable nitrogen content in optional ε phase on treated steel grades during the "boost" stages rich in nitrogen; 2. all "diffusion" stages are carried out in vacuum to separate the nitrogen reserve in nitrides from any external interactions. It enables the reliable modelling of nitrogen diffusive transfer based only on disproportionation więcej »

Changes of crystallite sizes in the layer determined on the basic of X-ray diffraction lines broadening

MONIKA GWOŹDZIK ZYGMUNT NITKIEWICZ

The X-ray diffraction is the main method for studying the oxidation product, which enables not only the identification of the product phase composition, but also allows determining crystallites sizes, their orientation and basic parameters of the scale crystal lattice. Depending on the chemical composition of the material and the component operating temperature, the oxide layers can consist of one or of many layers. The X-ray analysis enables examining the layer on its whole cross-section and is the basis for the studies on the oxidation mechanism [1÷16]. It is widely known that there is a close correlation between the X-ray diffraction pattern and the crystalline structure of the preparation. The experience of numerous researchers shows that the diffraction line structure (half-value width) depends on the size of given material crystallites [12, 16÷19]. Diffraction lines may be broadened also due to various imperfections of the crystalline structure, so-called lattice distortions. The study comprised calculations of crystallite sizes and lattice distortions of magnetite formed during a long-term operation at an elevated temperature for the main reflections originating from three planes: (311), (440) and (220). MATERIAL AND EXPERIMENTAL METHODS The material studied comprised specimens of 10CrMo9-10 steel taken from pipeline operated at the temperature of 575°C during 100 000 hours. The oxide layers was studied on a cross-section at the inner surface of the tube wall, is presented in Figure 1. A layer więcej »

Chemical modification of nanocrystalline titanium surface for biological applications

MARTA ZWOLIŃSKA AGATA ROGUSKA MARCIN PISAREK KAMIL ZAŁĘGOWSKI HALINA GARBACZ

Titanium and its alloys are the most attractive metallic materials for biomedical applications due to their unique properties, including low density, high corrosion resistance and good biocompatibility. However, for permanent implant applications, those materials may have harmful side effects resulting from alloying components released to the surrounding physiological environment [1]. This is especially dangerous in case of titanium alloys, such as Ti6Al4V, which is commonly used for heavy load implants. these alloys may have possible toxic effect resulting from vanadium and aluminium released to the body fluids. Nanocrystalline titanium due to its high mechanical properties is likely to replace the widely used titanium alloys [2]. Nanocrystalline or ultrafine grained (UFG) titanium can be obtained by several different processes, including: Equal Channel Angular Pressing (ECAP) [3], High Pressure Torsion (HPT) [4] and Hydrostatic Extrusion (HE) [5]. It has been revealed that the nanoscale grain refinement of titanium results in increase of hardness, elastic limit and tensile strength [5÷7] as well as fatigue strength [8]. Moreover, nanostructuring of titanium by SPD processing leads to increase in kinetics of chemical reactions. For example, the passive layer formed spontaneously on n-Ti has better protective properties since it is rebuilt in a shorter time [7]. Nanocrystalline and UFG titanium have been also recognized as promising biomaterials due to their ability to enhance the osseointegration process. It has been shown that cell attachment and proliferation as well as new bone formation were significantly increased on SPD processed titanium than on coarse-grained substrates [9÷11]. There are many various methods that can be used in the functionalization or activation of a metallic implant surface [12]. Among these methods, chemical modifications seem to be relatively simple and inexpensive [7]. In addition, they allow to więcej »

Determination of the phase composition in commercial Cr-Si-Mn steel after an austempering treatment

EMILIA SKOŁEK SZYMON MARCINIAK WIESŁAW ŚWIĄTNICKI

In recent years, a lot of research were dedicated to improvement in mechanical and functional properties of steels as the most widely used structural materials. High quantities of expensive alloying elements are usually added to obtain steels with high strength and good plasticity, what considerably raises their price (e.g. maraging steels). Therefore their competitiveness decreased comparing to the other materials. This is why other manufacturing methods are being sought to ensure high strength and good plasticity while maintaining moderate production costs. The production of nanocrystalline structure in the final components is one of the most promising ways of steels development. It was proven, that in steels containing a certain amount of Si, Mn and Cr, the carbidefree nanobainitic structure can be obtained applying a low temperature austempering. Such a structure consists of nanometric ferritic laths separated by thin layers of the retained austenite. Nanobainitic structure leads to high strength, while the appropriate content of retained austenite in form of thin films guarantees good plasticity and fracture toughness. The thin films of austenite forming a percolation structure inhibit the crack propagation, while the blocks of austenite may increase the ductility thanks to the TRIP effect based on the strain induced transformation of austenite into martensite [1÷4]. Thus, a precise determination of volume fractions of the phases in steel and their spatial distribution is essential for a better understanding of the impact of steel phase structure on its mechanical properties. It will also allow to design heat treatment which gives the phase structure ensuring obtainment of the desired properties. In this work, the phase structure in Cr-Si-Mn steel was investigated. A special attention was paid to determine the content of retained austenite after various austempering treatments by means of dilatometric tests and microscopi więcej »

Effect of point defects in a two-dimensional phononic crystal on the reemission of acoustic wave

KONRAD GRUSZKA SEBASTIAN GARUS JUSTYNA GARUS KATARZYNA BŁOCH MARCIN NABIAŁEK

Phononic crystals (PC) in a rather broad sense are synthetic materials with periodically changing acoustic properties of the medium (eg. density and speed of propagation of the acoustic wave) and have been recently intensively investigated due to the wide application range as well as interesting physical properties of these systems [1]. In spite of considerable simplicity of the construction of such materials they enable the construction of frequency filters that will allow to suppress undesired frequencies. In some cases, with proper distribution of repetitive elements making up the crystal, PC allow to create sound barriers in any band of acustic spectrum. Certain frequency ranges which are subject to strong damping, i.e. when the phonons do not propagate through the crystal, are called phononic band gaps. Significant impact on the parameters of phononic crystals has location and the distance between the periodic components, which by the appropriate arrangement are allowing to modify the center frequency of the pass-filter, and thus adjust the position of band gap [2]. If the distance between these components are comparable to the acoustic wavelength of the incident wave, and the top layer of PC will be uniform across the width, the acoustic wave will leave the crystal plane with very good convergence even at considerable large distances from the sound source. This allows the construction of the so-called. directional speakers and opens wide possibilities of commercial use in many applications ranging from medicine up to military applications. Figure 1 shows the typical structure of two-dimensional PC. Fig. 1. Typical phononic crystal structure 1 - first material; 2 - second material: d - diameter of periodic element, a, b - distances between element centers Rys. 1. Typowa struktura kryształu fononicznego 1 - materiał pierwszy, 2 - materiał drugi: d - średnica części periodycznej, a, b - odległości między środkami elementów więcej »

Effect of rapid quenching on the copper wheel surface on the microstructure, surface development and microhardness of Fe86Zr7Nb1Cu1B5 amorphous ribbons

MARCIN NABIAŁEK

One of the tasks posed for scientific discipline, which is a materials science is the search for new materials and improvement of properties of already known ones. What, would have meant the wide understood industry, without modern materials that exhibit better and better functional parameters. The development of human civilization is possible thanks to the application, for everyday use, ever new materials, characterized by a significantly better functional properties [1]. Commonly, for the ship construction, is used carbon steel, which have a relatively high density [2]. Therefore, are sought the lighter materials, with good functional parameters, such as: excellent corrosion resistance, good durability and relatively low density of [3÷7]. Already in the seventies of the last century, were successfully introduced into shipbuilding, MgAl alloys, whose density was more than three times smaller than those of low-carbon steel [8]. Another example of materials, with unique properties are amorphous alloys [9]. They are, one of the newest groups of functional materials exhibiting a number of very interesting properties [10, 11]. Classic crystalline alloys with chemical compositions as amorphous materials exhibit significantly worse functional parameters [10, 11]. The question is, what is the reason for that? Amorphous materials have different structure than crystalline materials. So, different properties are expected, which are determined by the microstructure of the material. The arrangement of atoms in a volume of amorphous materials is chaotic, similar to liquids. In contrast, the atoms in the crystalline material, are arranged in relevant configurations, repetitive in a volume of material. In addition, the interaction between atoms of amorphous alloys, belongs to short-range type of interactions, while in the crystalline materials belong to long-range interactions. Changes in the atomic structure of metallic materials with the s więcej »

EN AW-AlMg1SiCu alloy matrix composite materials reinforced with halloysite particles manufactured by mechanical milling

LESZEK A. DOBRZAŃSKI BŁAŻEJ TOMICZEK MIROSŁAWA PAWLYTA KLAUDIUSZ GOŁOMBEK

EN AW-AlMg1SiCu alloy matrix composite materials represent a group of engineering materials which have been investigated in numerous scientific centers worldwide for years [1÷3]. The research involves mainly the production of materials in industrial environment which show repeatability of properties. The properties of composite materials are not the resultant total of the properties of their components, that is why the designing of technological processes is difficult and therefore the fabrication of such materials should be supported by strong scientific background, high engineering skills and very precise realization of their manufacture process [4, 5]. The mechanical milling and compacting and hot extrusion following them enable the production of nanostructural composite materials with constant cross-section, uniform distribution of the reinforcing phase and the size of its particles, and - consequently - improvement of the material mechanical properties. New phases are used as reinforcement in composite materials with aluminum alloy matrix mostly to restrict the defects caused by conventional reinforcement and to improve the usable properties of the newly developed composite materials [6÷8]. The unconventional reinforcement of the metal matrix composites may be the halloysite particles. Halloysite is the clayey mineral of the volcanic origin, characteristic of high porosity, high specific surface, high ion-exchange, and ease of the chemical treatment and machining. Halloysite is composed of the flat surface lamellae, partially coiled or in the form of tubes originating from the coiled lamellae [9]. Halloysite nanotubes are in the shape of polyhedron, hollow inside, cylindrical objects of 40÷100 nm in the diameter and of length up to 1.2 μm. Employment of halloysite as the reinforcement of the metal composite materials is the original assumption and features will make it possible to use this mineral in the innovatory więcej »

Environmental degradation of Ti alloys in artificial saliva and a role of fluorides

ANDRZEJ ZIELIŃSKI BEATA ŚWIECZKO-ŻUREK AGNIESZKA OSSOWSKA

Titanium and its alloys possess specific properties, among them high corrosion resistance and biocompatibility. Bioinertness of Ti assed in short time tests seems almost perfect: the corrosion rate in simulated body fluids varied between 0.01 and 0.1 μg/cm2d, and after 48 weeks from an implantation of the Ti6Al4V alloy into animal body, only traces of metallic elements were found in tissues [1]. The corrosion resistance significantly depends on acidity of solution: in lactic and formic acids the general corrosion of the Ti6Al4V alloy was observed after 4 weeks [2]. Even if titanium is bioinert in neutral solutions, corrosion may appear in physiological saliva [3]. The saliva can be assumed as relatively aggressive environment [4]. The weight corrosion rate in artificial saliva was assessed as 0.28 g/cm2. At pH = 3 or lower, the passive current density for commercially pure Ti increased markedly with decreasing pH. The corrosion was observed [5] in saliva as dependent on a surface state, with a few times higher corrosion after sandblasting than after polishing. Fluoride ions are aggressive ions for the oxide layers of Ti and its alloys. Their presence may initiate localized degradation by pitting and crevice corrosion. Such conditions may happen as the toothpastes and prophylactic gels contain fluoride ions. So far results are confusing. As shown in [6], the effect of fluoride ions was weak at pH from 6.15 to 3.0 but below the last value Ti and its alloys suffered from localized corrosion. On the other side, even if titanium revealed ion releases 0.01÷0.1 μg/cm2.d, similar as gold alloys, the ion release increased to 500 μg/cm2.d in presence of fluoride [7]. Low pH values accelerate this effect even more. Therefore it is recommended to avoid the presence of fluoride or to reduce contact time. In another paper [8] the strong effect of presence of fluorides on corrosion density was observed for pure Ti and Ti6Al4V więcej »

Evaluation of the degree of wear of rotational instruments used in dentistry

MONIKA GWOŹDZIK ZYGMUNT NITKIEWICZ MARCIN BASIAGA ZBIGNIEW BAŁAGA

Medical tools and instruments comprise a very wide as well as functionally and geometrically diversified group of products. Dental instruments are a special group of medical instruments. They are used irregularly and with varying intensity, they are in direct contact with a tissue environment and with body fluids, with agents used for sterilisation and disinfection, medicines, they are subject to operational wear and sometimes to damage. A relatively large number of used dental instruments results from the variety of functions fulfilled by these tools. An intensive development of technology causes continuously increasing requirements for materials, both in the field of operational life and of corrosive-erosive effect. The material wear proceeds mainly on the surface, therefore the development of surface treatments creates broad possibilities to manufacture products of required properties based on the existing materials. The use of surface engineering techniques enables forming the microstructure, phase and chemical composition, state of internal stresses in surface layers of processed materials (metallic, ceramic, plastic), so forming their practical properties, such as: corrosion resistance, resistance to friction and erosive wear, resistance to oxidation at elevated temperatures, increase in the fatigue strength as well as biocompatibility with the environment of tissues and body fluids [1ö15]. MATERIAL AND METHOD OF TESTS The studies comprised rotational instruments - commercial steel drills used in dentistry, modified according to various treatment options: więcej »

Fe40Al intermetallic samples sintered by pressure-assisted induction sintering (PAIS) method

DARIUSZ SIEMIASZKO RAFAŁ MOŚCICKI

Low density, high specific strength, high specific stiffness and enhanced resistance to wear, corrosion of FeAl alloys in comparison to steels and nickel-based alloys make them attractive for industrial usage [1, 2]. The mechanical properties of FeAl alloys highly depends on the aluminum content. For example, the yield strengths increase with the increase in aluminum content up to 40 at. % Al [2]. Casting is a traditional method of high-aluminum Fe-Al alloys manufacturing. However, during the sintering of Fe-Al alloys from elemental powders strong exothermic reactions (Self propagating High temperature Synthesis - SHS) take place [3]. This phenomenon is utilized during reactive casting named the Exo-melt™. Sikka et al. and Deevi et al. [4÷6] used the exothermic energy generated in SHS reaction to melt different intermetallics for casting. Another method of Fe-Al alloys fabrication is powder metallurgy (PM). Specimens obtain by the PM method possess desired geometry, satisfactory mechanical properties and density close to theoretical. In the present work, Fe40Al sinters were fabricated from elemental powders. The pressure-assisted induction sintering (PAIS) method was used to sinter the specimens. The PAIS apparatus was built at the Department of Advanced Materials and Technology of the Military University of Technology and designed for the production of massive sinters. APPARATUS Scheme and an overview of the apparatus for the PAIS is shown in Figures 1 and 2. The de więcej »

Ferroelectric and ferromagnetic properties of the (1-x)NiZnFeO4 -(x)Pb(Fe1/2Nb1/2)O3 composite

DARIUSZ BOCHENEK PRZEMYSŁAW NIEMIEC RADOSŁAW ZACHARIASZ PIOTR GUZDEK ARTUR CHROBAK GRZEGORZ ZIÓŁKOWSKI

According to the thermodynamic terminology of the multiferroics, they are some ferroics of II and III order which have simultaneously at least two spontaneously ordered subsystems among the states: ferromagnetic FM, ferroelectric FE, ferroelastic FES and ferrotoroidal FT [1÷3]. Possible application of the multiferroics depend, first of all, on a degree of mutual coupling of particular subsystems (magnetic, electric and elastic) [4]. Materials showing simultaneous electric (FE - ferroelectric, AFE - antiferroelectric or FIE - ferrielectric) and magnetic ordering (FM - ferromagnetic, AFM - antiferromagnetic or FIM ferrimagnetic) are called ferroelectromagnetics (FEM) [5]. In the ferroelectromagnetics both magnetic and electric properties can be controlled by external factors, such as: a magnetic field, an electric field, stress or temperature [6]. If a mutliferroic material is the ferromagnetic and the ferroelectric at the same time, then it will be characterized by magnetic response to a variable electric field, or inversely, a polarization change in the external magnetic field. This effect can be strengthened by making composite based on the ferrites and the ferroelectric materials (multiferroics, biferroics, ferroics). According to the classification, made by D. Khomsky, the mutliferroic materials can be divided into multiferroics of type-I and type-II [5]. PbFe1/2Nb1/2O3 (PFN) is one of the wellknown ferroelectromagnetic materials. It has a structure of the perovskite type of the ABO3 general formula, where A positions of the unit cell are filled with big ions of lead Pb, whereas B positions are filled alternately with (in a random way) ions of iron Fe and niobium Nb [7, 8]. According to the classification of D. Khomsky [5] PFN belongs to mutiferroics of type-I, in which ferroelectricity is connected with a displacement of ferroelectrically active ions d0 (Nb) from the centre of regular octahedrons - O6, whereas magnetism is więcej »

Formation of ferritic-bainitic structure with retained austenite in hypoeutectoid steel

ADAM GOŁASZEWSKI JERZY SZAWŁOWSKI WIESŁAW ŚWIĄTNICKI

The very important aim of developing new grades of steel is to obtain a specific structure which guaranties a combination of high strength and high ductility. A newly developed family of Advanced High Strength Steels (AHSS) meets such requirements to a large extent [1÷4]. These include different multiphase steels such as: Dual Phase (DP), Complex Phase (CP), and Transformation Induced Plasticity (TRIP) steels [1], which give the possibility of obtaining good mechanical properties through manipulating with the type of phase, its volume fraction and spatial arrangement. DP steels are ferritic-martensitic steels, whereas CP steels consist of at least three phases amongst: ferrite, bainite, martensite and austenite. Annealing in the intercritical region plays an important role in the process of forming phase structure in CP and DP steels, since it enables to manipulate with the volume fractions of austenite and ferrite. Another interesting subgroup of AHSS family is steels with TRIP effect, in which carbon-enriched austenite is formed as a result of precise control of phase transformations [2]. The aforementioned phase is transformed into martensite during plastic deformation, which prevents necking deformation and premature rupture [3]. The presence of martensite in addition to ferrite (in the DP steels) results in limited formability when plastic forming methods are used [4]. Replacement of martensite with bainite in such grades of steels may increase this property [4]. In this paper, an attempt to produce a complex-phase steel with ferritic-bainitic structure with retained austenite was described. To form such a structure the process of annealing in intercritical region was used in order to obtain defined fractions of austenite and ferrite, followed by quenching with an isothermal holding in the bottom range of temperatures of bainitic transformation. It was assumed that the presence of retained austenite would increase ductil więcej »

Improvement of mechanical properties of Fe-based alloys by application of rapid solidification method and Ti doping

JOANNA GONDRO KATARZYNA BŁOCH MARCIN NABIAŁEK MARCIN DOŚPIAŁ MICHAŁ SZOTA ANNA BUKOWSKA PAWEŁ PIETRUSIEWICZ

Nowadays, the industry is looking for the modern functional materials with unique functional properties [1, 2]. Very interesting group of alloys for special applications are those made on the basis of iron modified with titanium. These alloys, due to their increased strength and relatively low density (ρTi = 4.507 g/cm³), can be used in many industries. Ti admixture in this type of alloys results in a partial or complete oxidation of the surface, as the Ti has high affinity for oxygen [3]. Titanium is known to be an element well tolerated by the human body, and therefore it is successfully used in implantology [3, 4]. It is applied to produce cores, both for large hip implants, as well for mini dental implants. However, without proper chemical or mechanical treatment, titanium does not overgrown tissue and is only a foreign body. Recently, blasting method has been a very popular technique for refinement of the top layer of alloys containing titanium, regarding dental implants. The technique is very simple and cheap, but it is not without drawbacks as stratification because of grit used in mechanical polishing. Its small parts are sticking into the surface of the implant. What in turn leads to tearing down the structure of the surface. So, it can be stated that a lot depends on the grit used in the discussed process, which usually are small aluminum granules. The problem of aluminum contamination of dental implants has been eliminated by the chemical digestion process. Materials containing titanium are characterized by low weight and relatively high strength, they are used to build most of metal components used in the aerospace and military industry [5, 6]. Titanium alloys are also adopted in jewelry and become a good alternative to a few percent of the population showing an allergic reaction to silver, gold or platinum. They were also widely used in optics as part of eyeglass frames (flex-titanium, β-titanium). T więcej »

Influence of glow discharge assisted nitriding processes temperature on corrosion resistance of layers made of Ti6Al2Cr2Mo titanium alloy

AGNIESZKA BROJANOWSKA TOMASZ BOROWSKI KAROL POŁAWSKI JOANNA SAŁACH JERZY ROBERT SOBIECKI

Titanium and its alloys are more and more widely applied in various industry sectors as well as in medicine, among others in cardiac surgery, stomatology and for bone implants, e.g. heap joints or knee joints. It is due to their low density, good mechanical properties, corrosion resistance, and excellent biocompatibility [1÷4]. However, low hardness, poor frictional wear resistance, metalosis effect as well as high thrombogenecity in contact with blood limit titanium applications in medicine [5, 6]. In order to improve these adverse properties of titanium and its alloys, various surface treatment methods are used. One of them is glow discharge assisted nitriding which allows for producing diffusive layers of TiN + Ti2N + αTi(N) type, distinguished by high hardness, good frictional wear resistance and eliminating metalosis effect [7, 8]. This article presents the results of surface morphology, microstructure, phase and chemical composition as well as corrosion resistance tests of nitrided layers made of Ti6Al2Cr2Mo titanium alloy after the processes of glow discharge assisted nitriding at the temperature of 700°C, 800°C, 850°C and 900°C. TESTING METHODOLOGY Flat samples with 20 mm in diameter and 3 mm in thickness made of Ti6Al2Cr2Mo titanium alloy were examined. After grinding, polishing and degreasing, the samples were placed in a glow discharge furnace and submitted to the processes of glow discharge assisted nitriding with an application of parameters presented in Table 1. Microstructure and surface morphology of the produced layers and titanium alloy in the initial state were examined with the use of HITACHI S-3500N scanning electron microscope, equipped with secondary electron (SE) and backscatter electron (BSE) detectors as well as EDS spectrometer (examinations of chemical composition of layers in cross-sections). The examinations were made with the use of backscatter electron (BSE) detector and secondary electr więcej »

Influence of hot rolling and isothermal annealing on microstructure and mechanical properties of high carbon steel

KRZYSZTOF ANIOŁEK JERZY HERIAN MAREK CIEŚLA

Railroads consist, among others, of rail tracks and turnouts. Railway turnouts are complex structures of railroad sections which either fork or join intersecting tracks (Fig. 1, 2). In a turnout, in the place where stretches of rails intersect each other, the so-called frogs are used. The frog allows a rail-vehicle to ride through rail intersections. It is constructed using block sections, type KL60 or KL49, produced via hot rolling. Turnouts are especially exposed to abrasive or fatigue wear and to changes of shape as a result of high dynamic loads of cyclic nature which occur when track vehicles ride through the turnout [1]. The process of a mechanic destruction of the upper layer leads to undesirable changes of the dimensions and shape of the contacting rolling surfaces of a turnout element and a railway wheel. Measurements of the wear of block sections built-in in turnout frogs made in operating conditions have shown irregularities in the wear of the rolling surface profile throughout the actual frog point length and its plastic flattening. The measurement methodology is presented in the authors' paper [1]. The highest wear occurs in the actual frog point in the place of the biggest load and decreases as the distance from the frog point grows. Such wear is caused by a momentary increase of the dynamic load acting on a small area of the frog point rolling surface, which leads to an intensive wear and plastic flattening of the frog point as a result of the rail vehicle wheel hitting against it. For these reasons, materials used for the production of rail turnout sections must have specific properties and first of all, an increased resistance to abrasive wear and fatigue. High costs of rail turnouts operation and their replacement are the grounds for developing new materials or technologies which will allow producing sections of better durability than those currently in use. Carbon-manganese steels of grade R260 with a więcej »

Influence of solution heat treatment on the microstructure and hardness of the Ni-Ta-Al alloy with a high carbon content

PIOTR BAŁA

The microstructure and properties of tools have strong influence on their throughput and reliability what favours development of mechanization and automate of technological lines. An increased interest in the production of machine element made of advanced materials (such as high alloyed steels or titanium alloys) forces the development of tool materials being formed at high temperature. Steels are a typical material for tool production. For high temperature application hot-work and high speed steels are applied [1÷5]. The hot work steels containing from 0.3 to 0.6% C, up to 5% Cr and Mo, W and V are universally applied as tool materials for operations at high temperature. Usually, the most important property of the steel is high impact resistant, which is required to crack resistant. Therefore their microstructure does not include primary or secondary carbides. Tools made of these steels obtain functional qualities by toughening, i.e. combined quenching with medium or high tempering. Tempering of tool steels usually takes place in the temperature range: 550÷620°C. Strengthening is achieved by precipitation of alloy carbides of MC and M2C (V, Mo and W) type [1, 2]. Several tools have to operate at temperature above 600°C, sometimes even at 1000°C, at which quenched and tempered steels soften, causing rapid decrease in a lifetime of tools. A development of high temperature creep-resisting nickelbased alloys relied mainly on the modification of 80% Ni and 20% Cr alloy known for its good creep-resistance. On account of ineffectiveness of strengthening by carbides in high temperature, a hardening of Ni-based alloys was obtained by the intermetallic phase Ni3(Ti, Al), designated as więcej »

Korzystny wpływ powłok CaO w procesach wysokotemperaturowego utleniania stopów na bazie niklu lub kobaltu

AIDROUS H. CIENIEK Ł. HALEM N. KUSIŃSKI J. PETOT C. PETOT-ERVAS G.

Oxidation of nickel and cobalt base alloys has been a subject of interest for many years [1÷4]. However, there is still uncertainty with regard to many aspects, not least the influence of reactive cations, such as Ca2+, Zr4+or Al3+, for instance. This is mainly due to the complexity of the metal/oxide reactivity regarding oxygen. Then introduction of reactive elements as a surface coating of the metal has the advantage to eliminate their effect in the alloy diffusion processes. In the present study, an investigation into the influence of calcium both on the transport properties of Ni1–xO and Co1–xO single crystals and on the thermodynamic and microchemistry properties of these oxides [5, 6] was carried out. The results allowed us to have a better insight into the understanding of the influence of CaO coatings on the oxidation of Ni and Co base alloys. MATERIALS AND METHODS Corrosion experiments Nickel was taken as reference metal for this study. The specimens were square coupons (1 cm2 by 0.1 cm thick), prepared from high purity (99.995%) nickel powder, sintered at 1100°C under an argon-(5%) hydrogen gas mixture. The coupons were first oxidized at 1165°C for 30 h. The oxide scale was removed from one main surface (1 cm2), which was then polished to a 1 m diamond finish. This surface was subsequently coated with a thin layer of CaO, by reactively sputtering CaO target in an ambient of 7 Pa argon, during one hour. Oxidation experiments were carried out in Setaram thermobalance between 800°C and 1200°C, in więcej »

Microstructure and chemistry of Pb-Sn solder/ENIG interconnections

JOANNA WOJEWODA-BUDKA ZBIGNIEW HUBER LIDIA LITYŃSKA-DOBRZYŃSKA ANNA SYPIEŃ PAWEŁ ZIĘBA

The recent directive of EU concerning the restriction of the use of certain hazardous substances, like lead, in electrical and electronic devices, does not apply to such an equipment as missiles, battlefield computers, satellites space probes, computers installed in aircraft, production and processing lines cranes, lifts, conveyor transport, cars, commercial vehicles, aircraft, trains, boat systems, hydraulic excavators, fork-lift road maintenance equipment, harvester, pacemakers, solar arrays and watt balances [1]. One of the very important issue is the plating system of electroless nickel with immersion gold (ENIG) which has been widely used to finish solder pads of printed circuit boards (PCBs), as well as ball-grid array (BGA) and flip chip substrates in many mentioned above devices [2÷4]. The goal of the present study was to provide more details about the microstructure and chemistry of the solder joints on ENIG finish obtained with widely used Pb-Sn alloy. EXPERIMENTAL STUDY Copper pad (35 m thick) with 4÷6 m of deposited Ni-P layer and 0.075 to 0.125 m thick plating of immersion gold was covered with Pb-Sn solder paste (Alpha Metals, 62Sn36Pb2Ag, wt %). The Pb-Sn/ENIG samples produced in such a way were subjected to the sessile drop method by contact heating procedure described in [6] at 503 K for 5 minutes. Then, samples were crosssectioned and examined using the FEI E-SEM XL30 Scanning Electron Microscope (SEM) equipped with the EDAX energy X-ray dispersive spectrometer (EDS). The thin foils for the transmission electron microscopy (TEM) observations were all cut using the Quanta 3D Focused Ions Beam (FIB). The TEM studies were performed on the TECNAI G2 FEG super TWIN (200 kV) microscope equipped with High Angle Annular Dark Field (HAADF) detector integrated with the EDS manufactured by EDAX. RESULTS AND DISCUSSION The SEM image of the cross-sectioned plating after interaction with Pb-Sn so więcej »

Microstructure and mechanical properties of ODS steels sintered under high pressure

Reduced activation ferritic (RAF) steels are promising candidates for many structural applications in fusion and fission reactor plants due to their radiation resistance and low swelling 0. However, their safe operation window is limited to 600÷650°C because of ineffectiveness of strengthening mechanism, dissolution of precipitates and grain growth at that temperature [2]. As a result, the material loses its mechanical properties and may undergo significant creep. Oxide dispersion strengthening (ODS) is an effective approach to increase the operation temperature of additional 100°C [3]. The presence of homogeneously distributed yttria nanoparticles retard recovery and recrystallization processes and by that improve mechanical properties of the steels at elevated temperatures. Moreover, oxide nanoparticles act as trapping sites for structural defects and by that improve the irradiation resistance [4]. The major disadvantage of currently produced ODS steels is their brittleness and impact behaviour, which still remain unsatisfactory. One of the well known method of increase the ductility and impact properties of the ferritic steels is vanadium addition. Vanadium is strong carbide and nitride forming element, suppress the bainit formation and stabilize the ferrite [5]. Additionally, highest ductility of ferritic steels is achieved by a suppression of więcej »

Nanocrystalline structures obtained by isothermal treatment in bearing steels

JULITA DWORECKA KAROLINA POBIEDZIŃSKA ELŻBIETA JEZIERSKA KRZYSZTOF ROŻNIATOWSKI WIESŁAW ŚWIĄTNICKI

Steel is the most widely used of all metallic construction materials. It results from high strength parameters and stiffness of steel combined with its relatively low price. Increase in demands for construction materials caused by economic factors and the objective to improve competitiveness of products are now the driving force behind the research and development projects concerning steel. The projects aim at developing novel, nonstandard technologies that would allow to obtain unconventional microstructures in order to improve and optimize properties of steel. A particularly promising direction of these projects is related to obtaining nanocrystalline structure in steel. Such a microstructure provides high strength parameters and simultaneously high plasticity and crack resistance in comparison to conventional alloys of similar strength [1, 2]. Therefore, steel with nanocrystalline structure belongs to the most perspective materials to be used in the industry. At present, numerous studies on developing a novel generation of steel are in progress worldwide, with the aim of obtaining nanocrystalline structures by a bainitic transformation. In order to obtain microstructure of nanocrystalline bainite it is necessary to introduce certain specific alloying agents to steel and to carry out a precise heat treatment that would ensure a bainitic transformation. Nanocrystalline bainite could be obtained in specially designed steel grades that have the following basic chemical composition (wt %): 0.6÷1.1% C, 0.5÷2% Si, 0.3÷1.8% Mn, up to 3% Ni, up to 0.5% Mo, 0.5÷1.5% Cr, and up to 0.2% V [3]. Within the scope of this study it was an attempt to obtain bainitic nanostructure in two commercial grades of bearing steel: 100CrMnSi6-4 and 67SiMnCr6-6-4. Moreover, mechanical properties of these steels after the bainitic transformation were tested. EXPERIMENTAL STUDY Adequate content of carbon, silicon and manganese is essential for obtainin więcej »

Novel, Fe-based functional bulk amorphous materials obtained using suction casting method

MARCIN NABIAŁEK

Nowadays are being searched materials with better functional properties, than currently applied. For a sure, as such group of materials can be treated bulk amorphous alloys (BMGs), which are characterized by much better properties than their crystalline counterparts [1]. Metallic amorphous alloys are known since 70's of previous age when P. Duwez has found novel method at that time, for production amorphous metallic ribbons [2, 3]. This method was successfully adapted by scientists and industrials and is used to nowadays [4]. Amorphous ribbons are produced by injection of liquid alloy onto rotating with high linear speed (usually around 30 m/s), copper cylinder [4÷6]. Ingots of pre-alloy are made from melted, in plasma arc, proper quantities of atomic elements. Melting of ingots during production process is made in quartz capillary, using induction furnace of medium power [5]. Further, liquid alloy is injected from capillary under a pressure of neutral gas onto copper drum, rotating with linear velocity in range from 104 K/s to 106 K/s [1, 3, 6]. Such large cooling speed do not provide the possibility of producing a material with larger dimensions, which greatly limits the possibilities of its use. Therefore, for three decades were sought ways to produce amorphous materials with larger than the critical thickness of 100 microns, in the case of amorphous ribbons. Of course, during these thirty years, several alloys in the form of rods with a thickness of more than 1 mm were prepared, but recipe giving the possibility of systematic receiving bulk amorphous materials, were not found. The breakthrough came in 1989 when Akihisa Inoue and colleagues proposed three criteria giving the possibility of producing amorphous alloys with thicknesses previously unachievable [1]: 1. Alloy must consist of more than three components, 2. Atomic radii at least of the main alloying elements must differ by more than 12%, 3. The alloying ele więcej »

Numerical analysis of AZ31 alloy extrusion process by the ECAE method

TERESA BAJOR MARLENA KRAKOWIAK HENRYK DYJA

In recent years one can observe huge increase of demand for magnesium alloys. More than 90% of products made of magnesium alloys are the constructional cast components. However, during the last decade, AZ series alloys are widely analysed in terms of their plastic forming. Due to their high strength properties and good castability, these alloys are used to manufacture some constructional components in aerospace, automotive and electronic industry. Moreover, these alloys have got excellent stiffness, exceptional dimensional stability, a high rate of vibration damping capacity and high recycling capacity [1÷4]. Comparing to casting alloys, wrought magnesium alloys are more promising, which is the reason of the growth of interest in magnesium processing technology and manufacturing the high quality products with a low specific gravity. The increase in the use of magnesium alloys in a variety of industrial applications is the cause of multiparameter analysis of their deformability to improve the mechanical properties. Plastic working of magnesium alloys at room temperature is difficult because of their compact hexagonal crystallographic structure at the ratio c/a close to the ideal value. Thus, the magnesium alloys at room temperature are deformed by slip on the base plane, what gives a limited number of deformation systems. Deformation of AZ31 alloy is usually carried out in the temperature range of 250÷300°C at low speeds [5÷8], where the operating deformation systems (slip on the base plane and on the prism one) allow to achieve the appropriate properties of the tested material. At works [9, 10] the results of investigations concerning the influence of deformation rate and temperat więcej »

Numerical prediction of the thermodynamic properties of ternary Al-Ni-Zr alloys

JOLANTA ROMANOWSKA SŁAWOMIR KOTOWSKI

Phase diagrams are the most concise representation of a given system, and are crucial for understanding phase transformations, interfacial reactions, solidification and related changes in microstructure. Therefore, they are essential for the development of new multicomponent materials. Phase diagrams are determined by experimental methods such as: thermal analysis, microstructure examination, pressure measurements and others. However, the experimental determination of phase diagrams is a timeconsuming and costly task because the number of possible systems increases drastically with the number of elements. Experimental information for entire phase diagrams is available for most of the binary systems, but experimental information becomes increasingly sparse as the number of constituent elements increases (for ternary, quaternary and higher order systems) [1]. In this context, it is useful to estimate thermodynamic data of multicomponent systems from the constituent binary systems. There are many methods of modelling thermodynamic properties and calculations of phase diagrams in complex systems on the basis of thermodynamic properties of binary alloys constituting the complex alloy. Geometrical models and thermochemical model may be used for prediction of excess Gibbs energies of a ternary homogenous solution from the corresponding binary data. Methods of extrapolating thermodynamic properties of alloys into multicomponent systems are based on the summation of the binary and ternary excess parameters. The formulas for doing this are based on various geometrical weightings of the mole fractions. Binary compositions are chosen by using geometric correlations in the isothermal Gibbs triangle. Typically, the binary compositions are obtained from the intersection of an isogram, passing through the ternary composition of interest and the sides of the triangle. An isogram is a line of constant value of a given quantity, such as mole fr więcej »

Resistance properties of heat-resisting steel-based PVD coatings

MARIOLA SPALIK BARBARA KUCHARSKA EDYTA KULEJ JOLANTA WILK

The X8CrNi25-21 grade steel is austenitic heat-resisting steel used in power engineering. This steel owes its heat resistance to the high contents of alloy additions of nickel and chromium, whereby compact Cr2O3 chromium oxide films form on the steel surface at elevated temperature [1, 2]. Heat-resisting steels are also used for applying protective coatings, especially on elements less resistant to the high temperature. Due to their multicomponent nature, the most suitable method of applying coatings of heat-resisting steels is the plasma-assisted physical vapour deposition (PVD) method [3÷5]. The micro- and nanocrystalline structure of the coatings promotes the diffusion of chrome [6]. An additional increase in the heat-resisting properties of both the steel and the coating can be achieved by enriching their chemical composition with additions of silicon and aluminium [7÷9]. As a metallic alloy, steel is an electric current conductor, thus offering the possibility of being resistance heated, e.g. for heat treatment or heat resistance assessment purposes. Resistance heating also finds an application for joining steel sheets by welding [10]. In any case current thermal power P is used for heating up steel, which is the Joule-Lenz effect, being proportional to the square current intensity I and the resistance R of steel, according to the following relationship (1) [11]. P = R · I2 (1) The resistivity of steel depends on its chemical composition and ranges from 0.75 to 1.1 mm2/m [12]. The addition of Si causes an increase in steel resistance, which, in the case of electrical engineering applications, reduces the losses due to eddy currents. The increase in temperature results in an increase in steel resistance. The study described in this paper has determined the resistance of AISI 310S heat-resisting steel PVD coatings with aluminium and silicon additions introduced. In addition, the temperature stability of coati więcej »

Solidification of Fe-Zn sublayers during galvanizing process

DARIUSZ KOPYCIŃSKI EDWARD GUZIK WALDEMAR WOŁCZYŃSKI

Studies on the technology of producing hot-dip coatings can be considered fully successful when a mechanism responsible for the growth of these coatings is fully clarified. The research conducted for many years [1÷13] have proved that hot-dip coatings are composed of two main layers. The first layer directly contacting the substrate is an alloyed layer, usually composed of a few sublayers of the intermetallic phases. The second layer - the external layer - is solidifying on the surface of an alloyed layer when the galvanized product emerges from bath and is being cooled [3, 4]. It shows beyond doubt that in every case an analysis of the zinc coating structure should be based on the equilibrium diagram of Fe-Zn alloys, what is shown in Figure 1 and has been the subject of numerous investigations [10÷13]. The broken line in Figure 1 denotes the process temperature TR of the zinc bath used for hotdip galvanizing. The value of this temperature is used to estimate the required degree of undercooling więcej »

Solidification process of sintered AISI 316L austenitic stainless steel powder modified with boron-containing master alloy

MATEUSZ SKAŁOŃ MAREK HEBDA MAREK NYKIEL ANETA SZEWCZYK-NYKIEL JAN KAZIOR

Wrought stainless steels have wide range of applications as consequence of their corrosion resistance in aggressive environments. Powder metallurgy (P/M) technology can increase range of application of stainless steel through significant reduction of manufacturing costs by simplifying production process. Unfortunately, manufacturing by P/M process created, in structure component, undesired porosity which greatly reduces corrosive resistance of sintered steel. A reduced open porosity can be usually attained by forging or other mechanical treatment. Of course such an operations increase costs. In order to keep manufacturing costs on reasonable level, it is desired to eliminate porosity during already existing manufacturing process. One of the possibilities is proper chemical modification of base alloy to induce appearance of liquid phase during sintering in order to achieve high density sinter. Many researchers indicated boron as an excellent activator for sintering ferrous alloys. Boron added to iron creates lowmelting eutectic liquid (1177°C) which activates densification mechanisms: (i) particles rearrangement by decreasing friction forces among the particles, (ii) fragmentation of particles by liquid penetrating grain boundaries. Moreover, presence of eutectic liquid in some cases under specific conditions during sintering process may lead to appearance of non-porous superficial layer. Such a layer is characterized by the lack of solidified eutectic liquid what greatly improves corrosive resistance of sinter by eliminating electrochemical corrosion cells. The creation of nonporous superficial layer usually requires addition of the high amounts of boron (higher or equal to 0.4 wt %) which during cooling solidifies as a brittle eutectic on grain boundaries drastically lowering mechanical properties of sinter [1]. Loss occurs especially when solidified liquid creates the continuous network surrounding grains [2]. Dispersing of więcej »

Structural and chemical investigation into Ti/TiC coatings deposited with Cold Gas Spraying (CGS)

SŁAWOMIR KĄC GRZEGORZ SZWACHTA JAN KUSIŃSKI PAOLO MATTEAZZI ALBERTO COLELLA SERGI DOSTA JAVIER FERNANDEZ JORGE GARCIA-FORGAS

Nanostructured materials and coatings are a main subject in research and development thanks to their good physical and mechanical properties compared to crystalline materials [1]. Cold Gas Spraying (CGS) is a low-temperature method with deposition carried out in the solid substrates relative to conventional thermal spray [2]. The deposition is achieved through powder acceleration to supersonic velocities in the de Laval type nozzle [3] (Fig. 1). The technique was developed in the Institute of Theoretical and Applied Mechanics of the Russian Academy of Science in Novosibirsk [3]. The coating materials are injected into the carrier gas stream in nanopowder form at the inlet of the de Laval nozzle. It is accelerated in gas stream and propelled to the substrate with high velocities. In the special chamber gas is heated to temperature lower than the powder material’s melting point, before entering the nozzle [4]. Only particles which reach the velocity higher than the critical velocity could be deposited onto a substrate [5]. The low-temperature method, the very short time scales and the use of more or less inert carrier gases (nitrogen, helium) make the Cold Gas Spray technique useful for applications where it is vital to avoid oxidation, maintain stoichiometry and to retain properties of the powder in the coatings. In comparison to conventional thermal spraying, CGS has the another advantage of being simple to implement [6]. In the coatings titanium was used as a plastic binder. The hard titanium carbides improve wear resistance. The aim of this work is to present the results of microstructural and compositional investigation into Ti/TiC coatings deposited by means of supersonic spray więcej »

Structural characterization and properties of M-WO3 (M = Au, Pt) thin films prepared by pulsed laser deposition

AGNIESZKA KOPIA WOJCIECH MAZIARZ

A sensor for detecting and measuring gas concentrations should be characterized by appropriately high sensitivity, selectivity, a short response time and stability. These requirements led to a fast development of research on semiconductor-based gas sensors [1, 2]. The tungsten trioxide is the competition to others oxides compositions regarding low costs of production and high sensitivity in the presence of H2S, NOx, SO2. However, sensitivity of the sensor, its stability and working time highly depend on microstructure, thickness of film, grain size and grade of specific surface [3, 4]. M. Bendahan et al. [5] showed in their investigations, that using magnetron sputtering it is possible to obtain WO3 films sensitive to O3, however, the sensitivity depends on working temperature. WO3, Ag-WO3, Au-WO3 and Pt-WO3 films produced by means of magnetron sputtering method were investigated in the area of sensitivity and selectivity by M. Stankova et al. [6]. Authors showed that WO3 films coated with z 3÷4 nm layer of Au or Ag are sensitive to presence of H2S in CO2 at temperature T = 260°C, but not reacting when SO2 is present in CO2. F. Mitsuga et al. [7] produced WO3 films using laser ablation method and showed that the highest sensitivity to the presence of NOx presented films in the temperature 200°C. Investigations into the sensitivity of WO3, Au-WO3 and Pt-WO3 films produced with PLD method were done by H. Kawasaki et al. [8]. Authors observed sensitivity four times higher for Au-WO3 and Pt-WO3 films regarding pure WO3 at the temperature 300°C. In all the cases investigated WO3 films characterized high sensitivity to various gases at different temperature. These films properties allowed the temperature modulation and direct WO3 films to detection of specified gas to be applied. In our previous investigation [9] więcej »

Study of the surface layers of 18G2A steel after plasma surfacing with WC and Fe-Cr powders

ADAM PIASECKI DARIUSZ BARTKOWSKI ANDRZEJ MŁYNARCZAK

Surfacing technology allows for production of surface layers on any materials, on products of any chemical and phase composition, and any shape. Rods or powders made of ceramics, metals, cermets or plastics may be used as surfacing materials. This method is used to produce surface layers with special properties, such as wear and corrosion resistance, refractoriness and creep resistance [1÷7]. Plasma surfacing method consists of melting additional material (in the form of bulk or powder) along with substrate in plasma arc at temperatures of about 15 000÷20 000°C. Additional material and melted metalic substrate create a weld overlay in which substrate participation can reach tens of percent. Mechanical finishing is not necessary because weld overlays are homogeneous, and their faces are smooth [2, 5]. High hardness (WC - 2240 HV, B4C - 2800 HV), wear resistance as well as corrosion and oxidation resistance are the major advantages of carbides. Another important advantage is the high strength to density ratio as well as the high melting point (above 2000°C) [1, 5, 7]. The aim of this study was to determine microstructure, thickness, hardness and chemical composition of the surface layers produced on 18G2A steel by plasma surfacing. EXPERIMENTAL DETAILS The surface layers were produced using WC and Fe-Cr powders. The four different powder mixtures were used, and their percentage compositions are shown in Table 1. The rectangular specimens (width of 30 mm, length of 50 mm and height of 10 mm) were used for the study. The tungsten carbide used in the study was in the form of irregular crystals with sharp edges, and their size ranged fro więcej »

The analysis of chemical composition and segregation of elements in butt welds created using friction stir welding

PAWEŁ WIECZOREK ZYGMUNT NITKIEWICZ

Conventional fusion welding of aluminum die casting alloys is generally difficult due to the formation of blowholes by entrapped H2 gas and the fragile intermetallic compounds in weld metal friction stir welding (FSW). FSW is a relatively new solid-state joining technique and has been extensively developed for aluminum alloys, as well for magnesium, copper titanium and steel [1÷3] This process is effective for the welding of various aluminum alloys. However, only a limited number of studies have been carried out on the cast aluminum alloys [4÷6]. FSW enables materials to be joined below their melting point and the cast structure can be modified because of grain refinement, the fine dispersion of intermetallic compounds, no formation of blowholes with removing cast defects and the dendritic structure of the base metal. The aims of this study are to examine the chemical composition of precipitates in joints obtained using FSW method and to evaluate the effect of the welding parameters on the joint quality. EXPERIMENTAL PROCEDURES AND DISCUSSION OF THE RESULTS Three-millimeter thick EN AC-AlSi7Mg aluminum cast alloy plates were used in this study. Tab więcej »

The creation and shifts of band gaps in binary superlattices

JUSTYNA GARUS SEBASTIAN GARUS KONRAD GRUSZKA KATARZYNA BŁOCH MARCIN NABIAŁEK

Superlattices are intensively tested materials [1÷24], the filtering capabilities are particularly attractive [21]. Multilayers are characterized by the presence of the photonic band gap, so that electromagnetic waves (EMW) at the specific frequencies does not propagate them. Using emulation properties of multilayer systems allows pretesting of the structure and the design to get the specific characteristics of the electromagnetic wave transmission bands. This reduces the number of samples performed and reduces the cost of examinations. Transmission superlattices are calculated using the matrix method [18÷21] and by the method of finite-difference in the time domain for one-dimensional structures (1D FDTD) [22, 25]. MATRIX METHOD The transmission of the multilayer structure is calculated from the following equation: 2 out out in in 11 T n cos 1 n cos więcej »

The impact of manufacturing inaccuracies on the filtration properties of Thue-Morse aperiodic superlattice systems

SEBASTIAN GARUS KONRAD GRUSZKA JUSTYNA GARUS KATARZYNA BŁOCH MARCIN NABIAŁEK MARCIN DOŚPIAŁ MICHAŁ SZOTA

Multilayers constructed with advanced composite materials are used in solid state physics, optoelectronics, optics and modern photonics [1÷8]. This refers mainly to the ongoing work on photonic crystals [9÷15], optical fiber photonics [16], quasicrystals [17÷24] and multilayer structures [5, 25÷30]. By superlattice we mean alternating layers constructed with differing properties of suitable topological configuration of the constituent components. Prediction by Veselago [31] in 1968 materials, which characterized by a negative refractive index, and the first experimental confirmation of their existence in the year 2000 [32] led to increased research on interesting properties of these structures [33÷39]. Thanks to high technology of multilayer systems production with specified configuration, the types of materials and layer thicknesses [40÷44] and the presence of the photonic band gap has become possible to design an applicationspecific materials. Consequently, it has become reasonable to carry out possible most detailed simulation of specific properties for multilayer structures, escpecialy the transmission properties which are the subject of research in this paper. In order to investigate the transmission properties of the superlattice, two most commonly used methods which are complementary to each other are used. The first one known as finite difference time domain method (FDTD) [39] is based on the study of the behaviour of electromagnetic waves described by differential Maxwell equations using an iterative algorithm. Fast Fourier Transform (FFT) [39] made simultaneously with the simulation, allows to determine the frequency characteristics of wave leaving test structure. The use of the matrix method allows to obtain of more information on the electromagnetic wave transmission by multilayer medium, which is made of layers of dielectric materials or modern composite materials with a negative refractive index otherwise known więcej »

The influence of resin content on the mechanical and soft magnetic properties of composite prepared on the basis of the bulk amorphous materials

KATARZYNA BŁOCH MARCIN NABIAŁEK MICHAŁ SZOTA

Currently countless amounts of electrical and electronics equipment is produced annually, inside of which the latest generation transformer systems are located. In order to operate in portable devices, such as laptops or mobile phones is necessary to use components that during his work does not use large amounts of electricity. Therefore, the engineers working in the modern laboratories are looking for cheap, readily formable and energyefficient transformers. Such a product may be obtained by combining particles of amorphous material having good soft magnetic properties with various types of non-metallic tackifiers [1, 2]. Note, however, that too much of a non-magnetic tackifiers can affect the parameters deterioration of soft magnetic materials [3÷5]. The paper presents results of studies conducted for composites made of amorphous particles combined epoxy resin in an amount by weight of 2, 3 and 4%. EXPERIMENTAL PROCEDURE The material for study was prepared from plates of the Fe61Co10Y8Mo1B20 bulk amorphous alloy. The plates was crushed in a mortar and combined of the epoxy resin (Fig. 1a). The plates were crushed, and then fractionated using a sieve and platform shaker. The fraction used in the study is 100÷200 microns (Fig. 1b). The obtained particles are combined with the Epidian 100 resin in a hydraulic press at a pressure of 5 MPa for 30 s (Fig. 2). Then, the resulting composites were subjected to curing at 423 K for one hour. Thus prepared samples had the shape of rollers with a diameter of 5 mm and a height of about 3 mm. Structural measurements, for investigated materials, were performed using a BRUKER D8 ADVANCE X-ray diffractometer, that was equipped with copper radiation source. Measurements were carried out in the 2 angle range from 30 to 120 with measuring step of 0.5 and exposure time of 5 s. The structure of the samples was also examined by the use of a Zeiss Supra 25 microscope compa więcej »

Transmission in 3-layered system

MICHAŁ SZOTA

Light propagation in dielectric multilayer systems is an intensively studied area [1÷4]. Materials composed of thin layers by their properties are used in optics, solid state physics, optoelectronics and photonics. The internal structure of these materials creates the phenomenon of the photonic band gap. Which means that electromagnetic waves of certain length does not propagate in these materials. Understanding the behaviour of electromagnetic wave propagation in these structures can help to design materials with specific properties in the future and it is a current problem [5]. During the study succeeded in produce multilayer structures [6÷11], discovered quasicrystals [12÷19] and photonic crystals [20÷26], as well as fiber-optic photonic [27]. Theoretical prediction of the existence of metamaterials composites, materials with a negative refractive index as a specific analysis of Maxwell's equations, has Veselago in 1968 [28]. Their existence has been confirmed experimentally in 2000 [29], followed by a dynamic increase in the work of investigating the properties of these structures, which continues to this day [30÷39]. Current technologies allow the production of multilayer systems with nominal thickness of the layers [40÷44], allowing for experimental confirmation of the properties of simulated structures and their construction for specific applications. Due to the simplicity and the cost of it appears advisable to investigate the transmission properties of multilayer systems with a simplified structure. For such systems may include a three-layer structure of ABA. It is expected changes in the transmission structure according to the types of materials A and B, and in particular their refractive index. Probable are striking differences depending on the type of material used: RHM - right-handed media (positive refractive index - a typical dielectric material) or LHM - left-handed media (negative refractive index - a composit więcej »

Transmission in aperiodic Severin superlattices

MICHAŁ SZOTA

Multilayers are materials with very interesting physical properties [1÷22], particularly interesting is the propagation of electromagnetic waves (EW) in superlattices [20]. It should be noted, that the internal design of the system and the medium in which it is immersed has a significant influence on the transmission of electromagnetic waves [17÷21]. Therefore it is important to understand the behaviour of an electromagnetic wave for the widest range of structures, which will allow to design systems with given properties. Calculation of superlattice transmission was made using the matrix method [17÷20, 22] for the Severin's superlattice [23]. TRANSMISSION CALCULATION Electromagnetic wave propagation can be described by the matrix equation: out więcej »

TRIP steel topography examined by AFM (Atomic Force Microscopy)

MAGDA DRYJA ANDRZEJ LIS PAWEŁ WIECZOREK

Rapid development of automotive industry and strong competition in the car market makes that car designers are looking for the new materials with better properties, especially mechanical ones. One of the greatest achievements of contemporary metallurgy was development of modern materials for motorization such as multiphase structure steel. This particular group includes TRIP (Transformation Induced Plasticity) type steel. It comes under a new generation mild-alloy steel group characterized by a very good combination of strength and plasticity [1]. This combination of mechanical properties results from the structure of the steel which can be produced in the process of multiphase heat treatment. While heat-treating ferrite appears in the structure, as well as bainite, martensite and large quantities of retained austenite which while technological forming of the final product turns into martensite. The structure of the TRIP steel can be precisely shaped by the proper technological parameter selection of particular heat treatment phases [2÷5]. In most cases electron scanning microscopes (SEM) are used to obtain information about the surface. Application of AFM (Atomic Force Microscope) - atomic force in a microscope enables broadening of topographical characteristics of the studied sample`s surface. Atomic force microscope allows to process the picture of the surface in different environments without a vacuum of any kind or special sample preparation. Moreover, it enables quantity evaluation of a chosen surface feature, including statistical analysis of surface irregularities [3÷4]. In the paper surface measurement was made by semi-contact method with the use of oscillatory needle under which the więcej »

Wear resistance of dental burs with a diamond coating

MONIKA GWOŹDZIK ZYGMUNT NITKIEWICZ ZBIGNIEW STRADOMSKI MARCIN BASIAGA

The scientific work on extending the operational life of dental instruments - primarily dental drills - has been ongoing for many years. The expected characteristics distinguishing dental instruments in terms of their design and operation include: - high reliability, - safety of use for operators and patients, -ease of operation, - specific set of mechanical properties as well as geometry useful to perform a specific procedure, - corrosion resistance in operating conditions, - design enabling full sterilisation of the instrument or device, - ergonomic nature and aesthetics of the design and manufacture. Specific conditions existing in the human body create very strict criteria both for metallic materials used for implants and dental instruments as well as for the layers on their surfaces. Good biocompatibility, high adhesion to the basic metal, and corrosion resistance are only some of the requirements to be met when applying specific material in medicine [1÷13]. MATERIAL AND METHODS OF TESTS The studies were carried out on commercial dental drills with a diamond coat. Drills made of a corrosion resistant steel were covered with a nickel-diamond composite of varying diamond grain size. Drills of various shapes of the working part and also of varying grain size of the coat were used, inter alia drills designed to remove old fillings and crowns (the flame-shaped drills) as well as drills intended to prepare tooth tissue by grinding (round and flame-shaped drills). Long-term operational tests of dental drills were performed in a dentist's surgery. The operation consisted of a d więcej »