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

Abstract

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, α grains were gradually elongated and β grains were split. The α phase developed a fiber texture with <011¯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 α grains and globularization of partial β grains. The intensity of <011¯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 α grains and transformed β grains. The tensile strength was obviously higher than the annealed state due to smaller α plates thickness and dispersion strengthening effects. Refinement of transformed β grains and α plates thickness led to the higher tensile strength in the higher strain specimens.