High temperature deformation of a Cu40Zr44Ag8Al8 bulk metallic glass

The deformation behavior of a Cu40Zr44Ag8Al8 bulk metallic glass in its supercooled liquid region was investigated in compression. Strain rate jumps were carried out at various temperatures ranging from about Tg to Tg + 20 K. The results show that the alloy exhibits quasi-Newtonian behavior at the highest temperature with a transition to non Newtonian flow when temperature decreases and strain rate increases. The mechanical behavior has been analyzed in the framework of the free volume model. The material has been characterized after deformation at Tg + 20 K by XRD and comparison has been made with the same material simply held at high temperature for the same duration. It was observed that deformation slightly accelerates crystallization which results in a very important hardening on the stress–strain curve. However, even if there is no hardening at high temperature which suggests that no crystallization has occurred, some hardening is observed at room temperature even for short holding times at high temperature.