Lamellar orientation control of TiAl-based alloy by uniaxial compressive deformation at high-temperature in (α+β) two-phase region

Abstract

In this study, the orientation of (α+γ) lamellar structure in the TNM alloy (Ti-43.7Al-4 Nb-1Mo-0.1B) is controlled by high-temperature uniaxial compression conducted in the (α+β) two-phase region. The control of the lamellar orientation is focused on a control of α phase orientation because of being decisive for lamellar γ orientation. All true stress-true strain curves indicated the work softening due to dynamic recrystallization. The stress-strain curve behaviors were consistent with microstructure observation. The peak stress increased with a decrease in lamellar colony size. After deformation in the (α + β) two-phase region at 1543 K and 1573 K, where the content of α phase was dominant, a fiber texture with the (0001)α2 plane tilted 35° away from the compression plane was formed by the deformation mechanism of α phase. On the other hand, at 1623 K where the content of β phase was dominant, a double (0001)α2 fiber texture tilted at 35°- 45° and 80°- 90° away from the compression plane was observed. The double (0001)α2 fiber texture is considered to be caused by β→α phase transformation during cooling according to Burgers orientation relationship. Single-step uniaxial compressions conducted at the (α + β) two-phase region at different temperature (1543 K−1623 K) led to an inclination of (0001)α2to compression plane and subsequently lamellar interfaces of one colony unparallel to those of other colonies.