Effect of processing parameters on the morphology of α-phase in Ti-6Al-4V alloy during the two-step hot deformation

The morphology of the α-phase in titanium alloys considerably affected their physical and mechanical properties. In this research, the effect of applied strain and inter-pass times on the morphology of the α-phase was studied in the two-step hot deformation process. Hot compression tests were performed at 900 ºC and 0.001 s-1 while the strains in the first and second passes were set as (first cycle: 0.6 and 0.3) and (second cycle: 0.3 and 0.6) respectively, with various inter-pass times. The work softening parameter obtained from the stress-strain curves showed that the proper time for globularization of α-layers for the first pass strain of 0.6 was 240 s and for the second strain of 0.3 it was 240 and 300 s. Microstructure results indicated that the first pass strain of 0.3 and the inter-pass time of 240 s were the optimum conditions for globularization of α layers.