Effect of strain rates on the plastic deformation behavior and serrated flow of Zr55.7Cu22.4Ni7.2Al14.7 bulk metallic glass

Abstract

The effects of strain rates on the plastic deformation behavior and serrated flow of Zr55.7Cu22.4Ni7.2Al14.7 bulk metallic glass (BMG) were studied by compression test at room temperature. The results show that the plastic deformation behavior of metallic glass at room temperature is highly sensitive to strain rates. The plastic strain, yield strength, compressive strength and fracture strength were found to increase with decreasing of strain rates. For example, the plasticity and the compressive strength increased from 0.4 ± 0.1%–8.3 ± 0.4 %, and from 1684 ± 11 MPa to 2000 ± 23 MPa, respectively. In addition, the number and density of shear bands on the fracture side also increased gradually. The fracture morphology, which is mainly composed of vein-like patterns, can be understood by the fact that the number and density of vein-like patterns increase with decreasing of strain rates. However, the mechanism of serrated flow was analyzed and discussed from the perspective of the initiation, expansion, and interaction of multiple shear bands correspondingly. With decreasing strain rates, the uniformity of the serrated flow in the first stage is not sensitive to the change of strain rates, while the uniformity of the second stage serrated flow changes. The change of serrated flow from near uniformity to non-uniformity in the second stage is attributed to the interaction between multiple shear bands. In comparison, with decreasing strain rates, the stress drops in the second stage first decreases and then increases due to the interaction of shear bands. The plastic deformation behavior and serrated rheology of bulk metallic glasses (BMGs) at room temperature, which lay a foundation for promoting the engineering application of BMGs, were discussed in details in this study.