Microstructure and Mechanical Properties of Cu–Zr–Al Bulk Metallic Glass with Addition of Co

Abstract

(Cu₄₆Zr₄₆Al₈)_100−xCo_x (x = 0, 1, 2, 3 and 4) bulk metallic glasses (BMGs) were synthesized by copper mold casting, and the effect of Co addition on the microstructure and mechanical properties of Cu₄₆Zr₄₆Al₈ BMG was investigated. The existence of immiscibility gap between Co and the main component Cu is responsible for liquid separation to form droplet-type structure during solidification. The size scale for the droplet-type structure trends to increase with the Co concentration. Depending on the glass-forming ability of the separated liquid phase, amorphous/amorphous or amorphous/crystalline composite structure can be obtained. The results of compression test reveal that the plasticity and the fracture strength can be simultaneously enhanced with an appropriate amount of Co addition owing to nanoscale phase separation with the formation of Cu-rich and Co-rich glassy phases.