A study of hot deformation of Cd-1% Zn alloy using power dissipation maps

The hot deformation behavior of Cd 1% Zn alloy has been studied using hot compression testing in the temperature range 50-300 deg C and in the strain rate range 0.001-100 s exp -1 . On the basis of the flow stress data, processing maps showing the variation of the efficiency of power dissipation (given by 2m/(m+1), where m is the strain rate sensitivity of flow sterss) with temperature and strain rate are obtained. The material exhibits four domains: (1) dynamic recrystallization (DRX) domain at 250 deg C, 0.1 s exp -1 with a peak efficiency of approx40%; (2) dynamic recovery domain centered at 200 deg C, 0.001 s exp -1 with a maximum efficiency of 30%; (3) a superplasticity domain at 300 deg C, 0.001 s exp -1 with 64% maximum efficiency, and (4) cracking domain at 300 deg C, 100 s exp -1 with a maximum efficiency of 51%. Microstructures observed after DRX process are homogeneous with the grain size varying sigmoidally with temperature. Large variations in grain size and abnormal grain growth were observed after superplastic deformation. In comparison with pure Cd, DRX in Cd 1% Zn alloy occurs at a higher strain rate with a lower peak efficiency value. The change in DRX characteristics in Cd 1% Zn alloy is attributed to the possible decrease in the stacking fault energy (SFE) due to the addition of Zn. The instability criterion has predicted unstable flow at 200 deg C and 100 s exp -1 and the corresponding microstructures show bands of fine grains produced by static recrystallization after inhomogeneous deformation