Wyniki 1-10 spośród 13 dla zapytania: authorDesc:"Tadeusz Kulik"

Nanocrystalline Al-30%Fe alloy obtained by mechanical alloying and hot-pressing

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In the present study, mechanical alloying followed by hot-pressing consolidation has been used to obtain bulk nanocrystalline Al-30%Fe alloy. Nanocrystalline two-phase Fe(Al)+Al5Fe2 alloy was the product of mechanical alloying of Al-30%Fe powder mixture. The milling product was hot-pressed at 1000 °C for 180 s under a pressure of 7.7 GPa. Structural investigations of the consolidated material[...]

Thermal and magnetic properties of nanocrystalline alloys from Fe-Co-Hf-Zr-Cu-B system

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One of the most rapidly developing groups of magnetically soft materials are the nanocrystalline, iron-based alloys. Special interest concerns the materials obtained by partial crystallization of metallic glasses, with better magnetic properties than those found for the amorphous counterparts. Nanocrystalline magnetically soft materials are divided into three main groups: Finemets, Nanoperms [...]

Influence of silicon content on the microhardness of Al91-xSixNi7Mm2 rapidly solidified ribbons

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Rapid soldification is well known method to obtain alloys with nanometer grain size. The nanometer grains provide an increase of mechanical properties of the alloys. In the present work Al-Si-Ni-Mm (mischmetal) alloys were produced by melt spinning technique to obtain nanoscale grains embeded in amorphous matrix. The melt spun ribbons were invastigated by X-Ray difraction (XRD) and different[...]

Nanocrystalline Ni3Al-based alloys produced from aluminium scrap by mechanical alloying and subsequent heating

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As it is known, the reduction of grain size to the nanometer scale can improve the mechanical properties of materials. In this work, the nanocrystalline powders containing 75at.% of Ni and 25at.% of Al and other alloying elements were produced by ball milling of powdered aluminium scrap (silumins) with addition of Ni powder. The powders were investigated by X-ray diffraction after different s[...]

Influence of casting parameters on thermal properties of bulk metallic glass Cu48Zr36Ag11Ti5

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Bulk metallic glasses take their structure straight from the liquid. In opposition to the crystal metallic alloys they possess neither a crystalline structure nor its defects, such as vacancies, dislocations or grain boundaries [1]. This causes an extraordinary properties of this group of materials. As regards to their properties, metallic glasses differ significantly among each other, because of their sensitivity to even the slightest change of chemical composition. However, it is possible to describe same general features. Bulk metallic glasses exhibit high compressive strength (from 2 to 5 GPa) [2, 3] and relatively low Young’s modulus (70÷90 GPa) [4], what gives rise to an ability of accumulating a large amount of elastic energy. Moreover, they have very high wear resistance [5] that comes not only from the hardness [6], but also from very high surface smoothness [7]. These materials also exhibit very attractive formability. A characteristic temperature area of very high viscosity appears during heating before crystallization of the amorphous structure. This area is defined as ΔTx and is called a supercooled liquid region. It appears between the onset temperature of crystallization - Tx and the glass transition temperature - Tg: ΔTx = Tx - Tg. In this temperature region metallic glass is very susceptible for plastic deformation (that may reach 106%) and many little parts can be put together to produce one complex detail [5]. What is important, the amorphous structure is not lost after heating for short time [8÷10]. In addition, the parameter ΔTx is often being used to describe glass forming ability of a bulk glassy alloy. It means that alloys with higher value of ΔTx exhibit better glass forming ability. For this reason, the research effort is focused to find optimal manufacturing parameters of the glass with the widest supercooled liquid region. A lack of long range ordering (characteristic for amo[...]

Influence of silver on the glass forming ability and mechanical properties in Cu-Zr-Ti-Ag bulk metallic glasses

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Cu-based bulk metallic glasses (BMGs) exhibit promising mechanical properties: high fracture stress, large elastic strain, good fracture toughness and good corrosion resistance [1]. In addition, non-elastic flow has been reported in some new Cu-based systems [1, 2]. These glasses are also less expensive than currently exploited commercially Zr-based BMGs [3]. The unique set of mechanical properties of Cu-based BMGs is the reason for potentially wide application zone of these materials [4, 5]. However, their mechanical properties and glass forming ability (GFA) need to be improved even further before common industry usage. The aim of this work was to investigate the influence of silver addition on the GFA and mechanical properties of the Cu-Zr-Ti alloys. Chemical composition of examined alloys was prepared after following formula: Cu48Zr36Ti16 - xAgx (x = 0, 5, 8, 11, 13 at. %). The GFA was investigated on the basis of the temperature interval of supercooled liquid region (ΔTx). This region appears between the onset temperature of crystallization (Tx) and the glass transition temperature (Tg). In this temperature region bulk metallic glasses are very susceptible for plastic deformation. Moreover, it is possible to join many little parts together. Mechanical properties of the investigated alloys were determined by means of Vickers microhardness and room temperature compression test. EXPERIMENTAL The m[...]

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