A Series of Zr-Based Bulk Metallic Glasses with Room Temperature Plasticity

A group of plastic Zr-Al-Ni-Cu bulk metallic glasses (BMGs) with low Zr content was developed and their thermal and mechanical properties were investigated. The results show that these Zr-based BMGs have a single crystallization event for all heating rates in the studied temperature region. The glass transition temperature T_g decreases with increasing Zr content for all heating rates. There are two melting procedures for the BMGs whose Zr content is less than 52 at %, while three melting procedures for the other Zr-based BMGs. The second melting procedure is split into two melting procedures for Zr_52.5Al_12.2Ni_12.6Cu_22.7 and Zr₅₃Al_11.6Ni_11.7Cu_23.7 BMGs, while the first melting procedure is split into two melting procedures for the other BMGs. The activation energy decreases with increasing sensitivity index β for the studied Zr-based BMGs. The plastic strain ε_p is in the region of 0.2%-19.1% for these Zr-based BMGs. Both yield strength σ_y and fracture strength σ_f are smallest for Zr₅₅Al_8.9Ni_7.3Cu_28.8 BMG whose ε_p is largest among all studied Zr-based BMGs and reaches up to 19.1%. In addition, the mechanism for the large difference of the plasticity among the studied Zr-based BMGs is also discussed.