Formation and properties of Zr 48 Nb 8 Fe 8 Cu 12 Be 24 bulk metallic glass
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Zr/Nb-based bulk metallic glass (BMG) with a composition of Zr48Nb8Fe8Cu12Be24 was formed in cylindrical shapes 8 mm in diameter by the quartz tube water quenching method. The formation and acoustic, thermal, mechanical, and elastic properties of the BMG were investigated. The BMG exhibited excellent glass-forming ability, high thermal stability, and excellent mechanical properties. I. INTRODUCTION 1
In 1960, Duwez first synthesized Au75Si25 metallic glassy ribbons at Caltech, then, metallic glasses were soon realized to have considerable fundamental and commercial importance. After that, much research has been done on exploring new metallic glass-forming alloys. However, most alloys exhibit very low glass-forming ability (GFA), and extremely high critical cooling rates (>106 K/s) were required to form metallic glasses by the cooling from melts. In 1990s, metallic glass of La55Al25Ni20 alloy was formed with a critical cooling rate lower than 103 K/s.2 Since then, a number of glass-forming systems with excellent GFA, such as MgCuY, NdFeAl, ZrAlNiCu, ZrTiCuNiBe, PdNiCuP, and FeAlGaPSiB,3 have been exploited in bulk form. Zr41T14Cu12.5Ni10Be22.5 is one of the best glass formers without containing noble metals, developed by Peker and Johnson4 in 1993. This metallic glass can be formed at a slow cooling rate below 1 K/s, and its GFA is close to the oxide glasses. Bulk metallic glasses (BMGs) have been found to exhibit excellent elastic properties, high corrosion resistance, and superplasticity in the supercooled liquid region [SLR, is defined by the temperature interval between the glass transition temperature (Tg) and the onset crystallization temperature Tx , ⌬T ⳱ Tx − Tg].3 This offers great potential for engineering applications. On the other hand, the BMG is thermodynamically metastable; it has a tendency to transit to stable states when the temperature is higher or even lower than Tx . The lower thermal stability will severely restrict the wide applications of the BMGs. Thus the exploration of new glass-forming systems with higher thermal stability is rather important. Substitution with similar elements is an effective method in the exploration of new glass-forming systems. Table I shows some typical substitutions of the a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 16, No. 6, Jun 2001
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glass-forming alloys. It is well known that the properties of element Nb and Fe are similar to those of the Ti and Ni respectively, but Nb and Fe have higher melting temperatures. Therefore, the substitution of the latter with the former may be an effective way to improve the thermal stability of the BMG without impairing the GFA. Super-plasticity of the BMG is also of importance for industry, as it can be used to produce components having complex shapes from materials that are hard to machine.12 Previous research3 shows that the BMGs usually exhibit an inhomogeneous deformation behavior at a temperature of about 100 K below gla
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