The α2 precipitation from equiaxed γ phase in as-cast Ti-44Al-4Nb-2Cr-0.1B alloy

Abstract This paper presents the novel duplex microstructure in Ti-44Al-4Nb-2Cr-0.1B alloy during the heat-treatment of 1200°C/24h+1300°C/1h/FC, which precipitate two kinds of α2 phases from the equiaxed γ grains. The mechanisms of γ→α2 transformation in equiaxed γ grains were investigated. Two needle-like α2 variants can be observed inside one parent γ grain with the intersection angle of 71.4°. The irregular α2 were preferentially precipitated at γ grain boundaries with large disorientation, nucleated selectively in the γ grain whose {111}γ plane nearly parallel the γ/γ grain boundary, and grew into the neighbor γ grains with no orientation relationship.