Effects of Thermo-mechanical Treatment and Al Content on the Microstructure and Room Temperature Ductility in γ+α₂ Type Binary Titanium Aluminides

Abstract

Thermo-mechanical treatment conditions have been investigated on γ+α₂, type titanium aluminides to obtain a uniformly fine grained structure which is expected to exhibit a high ductility at room temperature. A higher working reduction, followed by a heat treatment at the temperature at which volume fractions of the γ and α phases are equal to each other is required to obtain the fine duplex microstructure consisting of the equi-axed γ and lamellar grains. The room temperature tensile elongation in such fine duplex microstructures strongly depends on the volume fraction of the α₂ phase. A higher Al content results in a high tensile elongation, especially 7.8% in the stoichiometric composition where small amount of α₂ are contained. The maximum elongation of 7.8% is substantially higher than those formerly reported.