Influence of Strain Rate on Compressive Deformation Behavior of a Zr-Cu-Ni-Al Bulk Metallic Glass at Room Temperature
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INTRODUCTION
BULK metallic glasses (BMGs) are new promising candidates for engineering and structural materials due to their favorable mechanical properties, such as extremely high strength, superior hardness, large elastic limit, unique fracture toughness, and excellent wear resistance.[1–7] It is true that many engineering materials, including BMGs, may experience deformation at various strain rates during service. Therefore, it is of particular interest to clarify their mechanical responses within a wide range of strain rates in order to extend their potential applications. Recently, the mechanical behaviors of BMGs at various strain rates, particularly at dynamic strain rates of higher than 103 s1, have attracted increasing attention from the materials science community.[8–17] To date, the relationship between the strain rate and compressive yield strength of BMGs has not been well established in the literatures. Bruck et al.[8] and Subhash et al.[9] demonstrated that the compressive yield strength of the Zr41.25Ti13.75Cu12.5Ni10Be22.5 BMG is essentially insensitive to the strain rate applied. However, Sun et al.[10] found that the yield strength of the Zr41.2Ti13.8Ni10Cu12.5Be22.5 BMG decreases under dynamic compressive tests, suggesting a negative strain-rate dependence of yield strength. Moreover, the negative strain-rate sensitivity to compressive yield strength was also reported in many other glass forming alloys, such as Pd40Ni40P20,[12] (HfxZr1–x)52.5Ti5Ni14.6Cu17.9Al10,[11] W. ZHENG, Postdoctoral Student, Y.J. HUANG, Senior Research Assistant, and J. SHEN, Professor, are with the State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, P.R. China. Contact e-mail: [email protected] G.Y. WANG, Senior Research Assistant, and P.K. LIAW, Professor, are with the Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996 USA. Manuscript submitted April 11, 2010. Article published online February 24, 2011 METALLURGICAL AND MATERIALS TRANSACTIONS A
Zr57Ti5Cu20Ni8Al10,[13] and Zr38Ti17Cu10.5Co12Be22.5.[14] On the contrary, the positive strain-rate dependence of yield strength was found in Ti40Zr25Ni8Cu9Be18[15,16] and Nd60Fe20Co10Al10 glasses.[17] The preceding conflicting results suggest that the intrinsic mechanism of the effects of strain rates on the compressive strength of BMGs remains a controversial issue. Apparently, many factors, including chemical compositions, loading mode, and sample shape, could play a crucial role on the nature of the strain-rate sensitivity of the yield strength in metallic glasses. Therefore, more experimental data are needed in order to gain more insights into the strain-rate dependence of the mechanical behavior of BMGs. In the present article, the compressive deformation behaviors of a Zr50.7Cu28Ni9Al12.3 (at. pct) BMG recently developed by Sun et al.[18] are investigated under quasi-static and dynamic compression. The influence of strain rates on mechanical behavior of the BMG studied is discu
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