Influence of the Crystalline Phase on Strain-Rate Sensitivity of a Zr-Cu-Ni-Al Bulk Metallic Glass at Room Temperature
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INTRODUCTION
BULK metallic glasses (BMGs), possessing a combination of exceptional properties including ultrahigh strength, high hardness, large elastic limit, unique fracture toughness, and excellent wear resistance, have attracted considerable interest from the materials science community.[1–7] However, monolithic BMGs always fail catastrophically along narrow shear bands when loaded in tension or compression, exhibiting very limited plasticity prior to fracture. The lack of plasticity has seriously restricted their widespread applications as structural and engineering materials. The development of bulk metallic glass composites (BMGCs) opens new prospects for the application of BMGs in modern industries.[8–13] The second phase, either ex situ or in situ, can serve as an effective barrier to the fast propagation of the shear bands, leading to multiplication, branching, and deflection of the shear bands,[13] thus resulting in the enhanced plasticity. Due to the combination of high strength and excellent plasticity, BMGCs have attracted longstanding attention[14] in engineering applications such as kinetic energy penetrators, where this kind of advanced material may be subject to a dynamic deformation condition. Therefore, it is of essence to clarify their mechanical responses to a wide range of strain rates in order to extend their potential applications. Recently, several efforts have been dedicated on investigating the dynamic responses of BMGCs using Split-Hopkinson Pressure Bar (SHPB) technique.[15–18] Li et al.[15] carried out the quasistatic and dynamic compression tests on four tungsten power-reinforced YONGJIANG HUANG, Senior Research Associate, WEI ZHENG, Ph.D. Student, and JUN SHEN, Professor, are with the School of Materials Science and Engineering and Key Laboratory of Micro-Systems and Micro-Structures Manufacturing, Harbin Institute of Technology, Ministry of Education, Harbin 150001, P.R. China. Contact e-mail: [email protected] Manuscript submitted February 5, 2012. Article published online August 7, 2012 5202—VOLUME 43A, DECEMBER 2012
and Vit106 Vit105 (Zr52.5Ti5Cu17.9Ni14.6Al10) (Zr57Nb5Cu15.4Ni12.6Al10) BMGCs, and it was revealed that the dynamic loading resulted in higher failure stress than the quasistatic loading. Wang et al.[16] conducted compression tests on a tungsten wire-reinforced Zr41.25 Ti13.75Ni10Cu12.5Be22.5 BMGC at different strain rates, and they found that the strain-rate sensitivity exponent of the composite is half of the monolithic tungsten. Hou et al.[17] and Ma et al.[18] investigated the dynamic mechanical properties of a tungsten fiber-reinforced Zr41.25Ti13.75Ni10Cu12.5Be22.5 BMGC at different temperatures, and they stated that its compressive strength decreases with increasing temperature. It should be noted that the abovementioned experiments mainly focused on the dynamic mechanical properties of ex situ composites. However, so far, little attention has been devoted to dynamic mechanical properties of in situ composites. In this article, Zr53Cu18.7Ni12Al16.3 (at. pct) all
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