Effects of multi-pass drawing strain and heat treatment on microstructure, texture and mechanical properties of Ti-6Al-4V alloy

In this study, a rolled Ti-6Al-4V alloy bar was processed by multi-pass drawing till 60% strain. The drawn state specimens were annealed and solid solution aged. The microstructure evolution characteristics, texture evolution features and mechanical properties changes were systematically investigated. During drawing, alpha grains were gradually elongated and beta grains were split. The alpha phase developed a fiber texture with < 01<(1)over bar>0 > parallel to the drawing direction, and the texture intensity increased with increasing the strain. The yield strength and ultimate tensile strength increased up to 1164 MPa and 1235 MPa respectively with increasing the strain. Annealing resulted in the recovery and the recrystallization of alpha grains and globularization of partial beta grains. The intensity of < 01<(1)over bar>0 > fiber texture decreased compared to the drawn state specimens. The tensile strength decreased and the ductility increased compared to the drawn state specimens and the strength followed the Hall-Petch relationship. After solid solution aging heat treatment, the microstructure consisted of primary alpha grains and transformed beta grains. The tensile strength was obviously higher than the annealed state due to smaller alpha plates thickness and dispersion strengthening effects. Refinement of transformed beta grains and alpha plates thickness led to the higher tensile strength in the higher strain specimens.