Influence of hot deformation process and annealing treatment on the microstructure of TC21 titanium alloy

Abstract

The TC21 alloy was subjected to hot compression tests at different strain rates (0.001 s^-1~10 s^-1), temperatures (890°C~1040°C), and deformation amount (0%~80%), followed by annealing at 900°C/1 h+AC. The microstructures of the samples were analyzed using OM, SEM, and EBSD techniques, and a systematic study of the microstructure evolution and flow softening mechanism was carried out, as well as an analysis of the variant selection phenomenon for the precipitation of α phase. The results show that the recrystallization mechanism of β grains in β region during deformation gradually changes from CDRX to DDRX with increasing strain rate and temperature; DRV is the dominant factor of the flow softening in the majority of deformation processes, which often occupies more than 50% of the contribution, and the contributions of deformation heat in α+β region and DRX in β region to flow softening cannot be neglected. The precipitated α phase will show the phenomenon of variant selection during the hot treatment in both α+β and β region, and the degree of variant selection decreases firstly and then rises as the deformation quantity increases, while it gradually decreases with the increase in temperature.