Abstract:The combined effects of isothermal annealing and pre-compression on the mechanical properties of Cu₃₆Zr₄₈Al₈Ag₈ bulk metallic glass (BMG) were investigated. The as-cast specimens were first annealed at 743 K for 10 min, and then pre-compressed under 800 MPa for 1, 3, 5 and 10 h, respectively. The results indicated that annealing resulted in the formation of nanocrystals with a diameter of ~10 nm in the amorphous matrix and a drastic decrease of the free volume, leading to complete loss of the plasticity of the BMG. Applying pre-compression under a stress of 800 MPa for a proper duration (5 h) resumed part of the lost free volume in the BMG matrix and therefore partially recovered the plasticity. A very long period of pre-compression (10 h) decreased the free volume again, which was caused by the excessive crystal growth.

Key words: bulk metallic glasses; annealing; pre-compression; free volume; nanocrystal