Pressure-dependent flow behavior of Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 bulk metallic glass
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An experimental study of the inelastic deformation of bulk metallic glass Zr41.2Ti13.8Cu12.5Ni10Be22.5 under multiaxial compression using a confining sleeve technique is presented. In contrast to the catastrophic shear failure (brittle) in uniaxial compression, the metallic glass exhibited large inelastic deformation of more than 10% under confinement, demonstrating the nature of ductile deformation under constrained conditions in spite of the long-range disordered characteristic of the material. It was found that the metallic glass followed a pressure (p) dependent Tresca criterion ⳱ 0 + p, and the coefficient of the pressure dependence  was 0.17. Multiple parallel shear bands oriented at 45° to the loading direction were observed on the surfaces of the deformed specimens and were responsible for the overall inelastic deformation.
I. INTRODUCTION
Since the discovery of the first metallic glass in the form of a thin ribbon by Klement et al.,1 many metallic glasses in binary and ternary alloy systems were developed prior to the 1980s.2–4 However, high critical quenching rate (103–107 K/s) required to form these metastable materials imposed a limit on the attainable sizes (typically smaller than a millimeter) for these metallic glass samples, mainly due to factors such as thermal stability and conductivity of these materials during the undercooling process. The scatter in geometric properties made accurate measurement of mechanical properties extremely difficult and less reliable. The application of metallic glasses as structural materials was impossible until the recent development of bulk metallic glasses of centimeter-scale thickness using relatively inexpensive materials and simple processing techniques in the last decade.5,6 One of the most important bulk metallic glass families, named Vitreloy family, has been recognized as an intriguing class of potential structural amorphous material (SAM). One of the most thoroughly studied bulk metallic glasses is Vitreloy 1,7 i.e., Zr41.2Ti13.8Cu12.5Ni10Be22.5 (commonly referred to as Vit 1), which has many desirable properties such as high specific strength and hardness, corrosion resistance, and near-net-shape casting ability.6,8–10 It is being applied as a structural material in coatings, electronic packaging, sporting equipment, and defense purposes.10 a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 18, No. 9, Sep 2003
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At elevated temperatures near or above its glasstransition temperature, Vitreloy 1 exhibits nonlinear viscoelastic behavior, and its deformation behavior can be well characterized.11 However, at low temperature (e.g., room temperature), the high strength metallic glass deforms elastically and fails in a brittle and catastrophic manner, although one may expect the material to be ductile because of its metallic bonding. While the study of high-temperature homogeneous deformation behavior11 can assist in understanding the net-shape thermal casting pr
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