Wyniki 1-5 spośród 5 dla zapytania: authorDesc:"Marcin Godzierz"

The interaction characteristics of liquid magnesium and selected magnesium alloys with open-celled glassy carbon foams DOI:10.15199/28.2018.2.3

  1. INTRODUCTION In the last decades, the developments in the technologies of carbon materials have caused new products usable as components in composite materials. In that group, we can find carbon fibers, glassycarbon particles, carbon nanotubes and graphene. At first, they were extremely expensive, but with time, they became cheaper and can be now commercially applied. Among the carbon materials, a new one has appeared, i.e. the glassy carbon open-celled foams (Cof), which, so far, have found applications as a sound absorption material, a biomaterial, a catalyst support or a thermal management material [1÷4]. The Cof are built of cells with walls containing windows and their geometry is commercially characterized by ppi (pores per inch), which means that the pore size increases with a ppi decrease [3, 5÷7]. That type of macrostructure gives the opportunity for carbon foams to be infiltrated by liquid media and to form interpenetrating phase composites [7÷9]. The research works focused on metal matrix composites report that continuous carbon fibers can be infiltrated by magnesium alloys, and magnesium matrix composites with dispersed carbon reinforcements as short fibers, particles and nanotubes can be processed by different powder technologies and casting methods [10÷16]. However, the results of wettability measurements are not unequivocal. If the equilibrium contact angle θ is less than 90°(socalled “good wettability state"), a spontaneous infiltration of molten magnesium into the porous fibres and open-celled preforms can be expected. The contact angle θ between the molten magnesium and the porous graphite as well as the vitreous carbon determined by Shi et al. [17] by the sessile drop method at 700°C in a chamber filled with argon and magnesium vapor was 80° and 74°, respectively. However, the works of other authors [18÷21] showed values higher than 90° as well as poor wettability. The contact angle estima[...]

Wear resistance of composites with Mg-Zn-RE-Zr alloy matrix and open-celled carbon foam DOI:10.15199/28.2019.2.3

  1. INTRODUCTION Magnesium and its alloys are currently used in the automotive industry for such parts as an inner door, tailgate, steering wheel core and column, seat frame, or wheel rims [1, 2]. Recent studies on development of magnesium alloys and magnesium matrix composites have focused on energy saving, weight reduction, and limiting environmental impact [2]. Nowadays, most magnesium components in the automotive industry are made of AM alloys (e.g.: inner door manufactured from AM50 alloy) or AZ alloys (e.g.: supports manufactured from AZ91D alloy). It was reported that some BMW engine blocks were also produced from magnesium alloys (six-cylinder inline combustion engine made from AJ62 alloy [2]). Magnesium-aluminium alloys can be characterized by good castability [2÷4], because of that, they can be applied in a high-pressure die casting (HPDC) process [1÷4]. However, creep properties of those alloys are lower than magnesium alloys containing rare earth elements (RE), because of that, that type of alloy is more often applied for wheel rims or gearboxes. Because of zirconium presence (applied in order to grain refinement [5]), those alloys can be sand casted [6, 7]. Wear properties are especially important when magnesium alloys are applied for critical automobile parts such as air intake, transmission, or suspension system [8÷11]. Literature shows that reinforcing magnesium matrix composites with glassy carbon particles (Gcp) or short carbon fibers (Csf) improves wear resistance of composites [12÷15], while some decrease of density was noticed [13÷15]. However, application of particles or short fibers as reinforcement can cause technological problems because of stability loss by Mg-C suspension, related to differences in components densities [16]. The segregation of carbon reinforcement in composite occurs in the form of two zones: Gcp - a rich zone (top of suspension, effect of less Gcp density) and an α-Mg zone. App[...]

Oxidation behavior of Co-Al-Mo-Nb and Co-Ni-Al-Mo-Nb new tungsten-free y-y' cobalt-based superalloys DOI:10.15199/40.2017.9.5

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Nowadays, the development of heat-resistant materials is crucial for aircraft industry due to the fact that turbine engines performance increasingly depends on high temperature stability of components, therein turbine blades and combustion sectors. From the other site oxidation and hot corrosion, concomitant to high temperature are the main mechanisms leading to faster degradation of materials used it this type of engineering systems [4]. Lifetime of high-temperature elements can be decreased owing to usage of low quality fuels, containing sulphur, sodium and halides impurities. This type of atmosphere promotes formation of liquid flux, which dissolves oxide layers protecting metal and causes increase of oxidation rate. Diffusion of sulphur into alloy results in sulphides formation and the corrosion damage development [2, 5, 9]. The solution providing hot corrosion protection for nickel-based superalloys is utilization of special barrier bond coatings, however this method is expensive and technologically demanding. Protective band coatings enhance hot corrosion resistance, whereas are still not suitable for long exposure at high temperature, therefore development of a new materials with comparable high temperature strength and greater oxidation and hot corrosion resistance is necessary [8]. Nickel-based superalloys are commonly used materials for high temperature applications, whereas cobalt-based alloys are utilized as well. Conventional cobalt-based superalloys exhibit remarkable corrosion resistance, mechanical properties at high-temperature and thermal fatigue resistance [11]. This type of alloys is based on solid solution of refractory elements (W, Mo, Nb, Ta) in fcc cobalt matrix, further strengthened by various carbides, therein M23C6, M7C3 and MC carbides [14]. Further investigations aimed in search of cobalt-based alloys with comparable mechanical properties to γ’ strengthened nickel-based alloys. It was repor[...]

Influence of leather tanning waste addition and sintering parameters on physical and mechanical properties of ceramic granules DOI:10.15199/28.2016.3.7

  This paper presents results of manufacturing the ceramic porous granules made of the local waste materials. These granules were produced from the mixture of the car wind-shield glass contaminated by residuals of the PVB foil and aluminosilicate-based mine slates. Addition of the leather tanning wastes was used in order to increase granules porosity without significant decrease of mechanical properties. The paper shows the effect of tanning wastes addition and sintering parameters on the properties of the resultant granules in comparison to the leather-free product. Porosity, apparent density and water absorption were examined according to EN 1097 standard, and compressive strength was examined according to UNE-EN 13055-1 standard. Differences in the microstructure of granules were examined using scanning electron microscope. Partial substitution of both starting materials by tanning wastes and/or the two-step sintering regime could significantly improve the physical properties, what has been shown in the present paper. Key words: ceramic granules, leather tanning waste, recycling, waste management, windshield glass. Inżynieria Materiałowa 3 (211) (2016) 131÷136 DOI 10.15199/28.2016.3.7 © Copyright SIGMA-NOT MATERIALS ENGINEERING 1. INTRODUCTION Nowadays, there are several issues related to recycling the car windshield glass. One of these problem is related to the layered structure of a car windshield. Two layers of glass are separated by a polymer layer of polyvinyl butyral (mainly known as PVB), which improves mechanical properties of the laminated material but simultaneously it prevents the separation of layers in the waste glass during a mechanical treatment. Advanced technology allows to separate those layers during screening resulting in separation of PVB as a large-sized fraction from the fine glass powder. It is impossible to produce the windshields again from these materials, but the PVB scraps can be used once more as an[...]

Oxidation performance of Co-Al-W and Co-Ni-Al-W new type of y-y' cobalt-based superalloys DOI:10.15199/28.2017.4.2

  Development of high efficiency turbine engines leads to evolution of heat-resistant superalloys of different types. The nickel-based superalloys are still being the most frequently used in high temperature applications, whereas new types of γ-γʹ cobalt-based analogues are becoming gradually more effective and popular [1÷3]. These alloys exhibit better oxidation, corrosion and wear resistance than Ni-based alloys, although have inferior strength. Solidus temperature of these alloys is 100÷150°C higher than those of commercial nickel alloys, such as CMSX-4 [4, 5]. The microstructure of γ-γʹ Co-based superalloys contains face-centered cubic matrix γ, strengthened by γ′ phase, which is a ternary compound with the L12 structure and usually Co3(Al, W) formula [6]. Furthermore, in the microstructure occurs variety of carbides (M23C6, M7C3 and MC). In fact, formation of γ′ phase is difficult due to required value of lattice mismatch less than 1% [7]. The γ′ Co3(Al, W) exists owing to Al and W content. The alloying elements such as Ti, Ta, Nb, Mo and V promote the γ′ formation and increase solvus temperature. It is also confirmed that the phase stability of the γʹ phase greatly increases by Ni substitution for Co because the Ni3Al with the L12 structure is very stable and the γʹ phase exists in a wide composition range in the Ni-Co-Al ternary phase diagram [8]. One of the most popular alloy from this group is tungsten containing Co-9Al-9W and Co-20Ni-7Al-7W (at. %) alloys [9, 10]. Co-Al-W alloys after high temperature oxidation are characterized by multilayered oxide structure [11, 12]. Surface layer has been characterized as cobalt monoxide, which is harmful to humans and dangerous for the environment. Middle layer consists of mixed oxides of Al, W and other elements present in alloy [13]. Furthermore, several authors reported an external Al2O3 scale in cobalt-based[...]

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