The microstructure evolution and tensile properties of Ti–43Al–4Nb–1Mo-0.2B alloy during hot rolling

Abstract

Ti–43Al–4Nb–1Mo-0.2B (at.%) (TNM) alloy sheets were fabricated, and the corresponding microstructure developed from lamellar to duplex structure with the rolling reduction increased from 50% to 72.5%. Interestingly, a novel Z-type lamellar structure developed at 67.5% deformation strain, and the formation process was discussed by calculating the Schmid factor. Moreover, α2+γ→βo phase transformation occurred at the kink band boundaries. Subsequently, as the reduction increased to 72.5%, the coarse βo phase decomposed and transformed to α2+γ phases due to the distortion energy stored after multi-pass rolling. Finally, the room-temperature tensile properties of the TNM sheets were tested. With the comparison of the as-forged alloy, the strength and ductility increased significantly by hot rolling, and the ultimate tensile strength reached 880 MPa at 60% total reduction. The relationship between the rolling process, microstructure evolution, and corresponding properties was established.