Designing Zr-Cu-Co-Al Bulk Metallic Glasses with Phase Separation Mediated Plasticity

摘要

New Zr-based bulk metallic glasses (BMGs) with improved plasticity were developed in the Zr-Cu-Co-Al system by a combination of Zr45Cu50Al5 and Zr55Co25Al20 BMGs with a certain concentration ratio. The compressive plasticity of the investigated alloys depends strongly on the concentration ratio of the two BMGs. Because of the positive enthalpy of mixing between Cu and Co (ΔHCu-Co = +9 kJ/mol), a strong repulsive interaction between Cu and Co is introduced, whereas an attractive interaction exists among the other constituent elements in the liquid state. When two BMGs are combined at a 1:1 concentration ratio, a maximum compressive plasticity of ~12 pct is achieved for the Zr50Cu25Co12.5Al12.5 BMG. The plasticity enhancement is attributed to atomic-scale chemical/structural fluctuations achieved through liquid-phase separation.