Microstructure Evolution during High Temperature Deformation of Ti-6Al-4V Alloy

Abstract

Abstract The effect of processing parameters, including deformation temperature, strain rate and deformation degree on the microstructure evolution and the microstructure variables (grain size and volume fraction of primary α phase) was investigated based on the microstructure observation and the quantitative metallography of the isothermally compressed Ti-6Al-4V alloy. The results show that the curves of grain size of primary α phase are oscillatory in the α+β two-phase region with increasing of the deformation temperature, and meanwhile the volume fraction of primary α phase decreases. The effect of the strain rate on the morphology of primary α phase is significant, while its effect on the microstructure variables of isothermally compressed Ti-6Al-4V alloy is dependent on deformation temperature. The grain size of primary α phase decreases with increasing of strain rate above 1203 K, but below 1203 K it fluctuates. The curves of volume fraction of primary α phase are oscillatory with increasing of strain rate above 1223 K, but below 1223 K the volume fraction decreases. The grain size of primary α phase increases slightly after a drop with increasing of the deformation degree, and meanwhile the secondary α phase decreases gradually. The effect of deformation degree on the volume fraction of primary α phase is not significant.