Applicability of Pre-Plastic Deformation Method for Improving Mechanical Properties of Bulk Metallic Glasses

Pre-plastic deformation (PPD) treatments on bulk metallic glasses (BMGs) have previously been shown to be helpful in producing multiple shear bands. In this work, the applicability of the PPD approach on BMGs with different Poisson's ratios was validated based on experimental and simulation observations. It was found that for BMGs with high Poisson's ratios (HBMGs, e.g., Zr₅₆Co₂₈Al₁₆ and Zr₄₆Cu₄₆Al₈), the PPD treatment can easily trigger a pair of large plastic deformation zones consisting of multiple shear bands. These PPD-treated HBMGs clearly display improved strength and compressive plasticity. On the other hand, the mechanical properties of BMGs with low Poisson's ratios (LBMG, e.g., Fe₄₈Cr₁₅Mo₁₄Y₂C₁₅B₆) become worse due to a few shear bands and micro-cracks in extremely small plastic deformation zones. Additionally, for the PPD-treated HBMGs with similar high Poisson's ratios, the Zr₅₆Co₂₈Al₁₆ BMG exhibits much larger plasticity than the Zr₄₆Cu₄₆Al₈ BMG. This phenomenon is mainly due to more defective icosahedral clusters in the Zr₅₆Co₂₈Al₁₆ BMG, which can serve as nucleation sites for shear transformation zones (STZs) during subsequent deformation. The present study may provide a basis for understanding the plastic deformation mechanism of BMGs.