Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Piotr Błyskun"

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[...]

Fractographic discoveries: investigation of bulk metallic glasses fracture surfaces after static compression test DOI:10.15199/28.2015.2.1

  The aim of these studies was to broaden the knowledge of bulk metallic glasses failure mechanisms. Two glass forming systems: Zr48Cu36Al16 - xAgx (x = 0, 6, 12, 16 at. %) and Cu48Zr36Ag16 - yTiy (y = 3, 5, 8 at. %) were selected for the studies. Rod shape samples with a diameter of 3 mm were produced from pure elements by the copper mould casting. X-ray diffraction allowed to determine the crystalline phase presence within the samples (Fig. 1). Both partially crystalline and fully amorphous samples were subjected to the static compression tests. The fractography of the resultant scraps was performed by the scanning electron microscopy. The studies reveal several new issues and confirm a few already known related to deformation and fracture mechanisms of metallic glasses. Authors carefully observed and insightfully discussed issues like: main fracture surface exclusiveness for vein-like patterns (Fig. 2), plastic strain implementation by the slip bands proliferation (Fig. 3), vein-like pattern development degree dependence on the fracture stress (Fig. 4), temperature rise relics presence on the main fracture surface (Fig. 5) or determining the origin of a crystalline phase just by the fracture surface observations (Fig. 6, 7). The results presented in this manuscript might be useful for future materials expertise that would potentially be done on metallic glass scraps from failed constructions. Key words: bulk metallic glasses, compression tests, scanning electron microscopy, fractography. Fraktografia przełomów masywnych szkieł metalicznych po statycznej próbie ściskania Celem pracy było poszerzenie wiedzy o mechanizmach zniszczenia masywnych szkieł metalicznych. Do badań wybrano dwa układy szkłotwórcze: Zr48Cu36Al16 - xAgx (x = 0, 6, 12, 16 at. %) i Cu48Zr36Ag16 - yTiy (y = 3, 5, 8 at. %). Z czystych pierwiastków wytworzono pręty o średnicy 3 mm metodą odlewania do formy miedzianej. Badania dyfrakcji promieni rentgenowskich pozwoliły ustalić[...]

Influence of silver on glass forming ability and mechanical properties of Zr-Cu-Al alloys DOI:10.15199/28.2015.4.1

  The work focuses on studying the influence of silver content on the glass forming ability and the mechanical properties of the Zr48Cu36Al16 - xAgx alloys (x = 0, 2, 4, ..., 16 at. %). Rods with a diameter of 3 mm were manufactured by the copper mould casting. X-ray diffraction studies (Fig. 1) revealed that samples with 6÷14 at. % of silver content were fully amorphous. Differential scanning calorimetry (Fig. 3) allowed selecting the alloy that possessed the best glass forming ability on the basis of the supercooled liquid region width (ΔTx). The Zr48Cu36Al6Ag10 alloy exhibited ΔTx = 91 K. Mechanical properties of the alloys were characterized by means of Vickers microhardness (Fig. 5) and room temperature compression tests (Fig. 6). The highest value of microhardness was detected for the partially crystalline Zr48Cu36Al16 alloy (791 HV). However, the highest compression strength was measured for the Zr48Cu36Al12Ag6 alloy (σc = 1881 MPa). It should be noticed that a plastic strain was observed in the fully amorphous alloys. On the other hand, partially crystalline samples cracked catastrophically without any observable plastic strain. These studies revealed that the silver content increase resulted in the microhardness and the compression strength decrease. Good mechanical performance and satisfying glass forming ability of the fully amorphous alloys examined at this work seems to be promising set of properties for structural applications. However, the Zr48Cu36Al4Ag12 is the most promising one. Key words: bulk metallic glasses, Zr-Cu-Al alloys, silver addition, glass forming ability, mechanical properties. Wpływ srebra na zdolność do zeszklenia i właściwości mechaniczne stopów z układu Zr-Cu-Al Praca dotyczy określenia wpływu dodatku srebra na zdolność do zeszklenia i właściwości mechaniczne stopów Zr48Cu36Al16 - xAgx (x = 0, 2, 4, ..., 16% at.). Pręty o średnicy 3 mm odlewano do formy miedzianej. Badania dyfrakcyjne promieni re[...]

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