Equiaxed α microstructure evolution in wrought Ti-10Al-1Zr-1Mo-1Nb alloy during annealing

Abstract

Evolution of alpha microstructure on the thermomechanical treated Ti-10Al-1Zr-1Mo-1Nb alloy during annealing was studied. The solution-treated materials were groove-rolled or uniaxially compressed in the alpha+beta region and annealed at 1173 K. The flow softening behavior and crystal rotation in alpha platelets revealed an evolution of deformation texture. The volume fraction of equiaxed alpha grains was increased during annealing. Especially in the material compressed at a strain rate of 1 s(-1), the equiaxed alpha grains developed within a shorter annealing duration than 1.8 ks. The deformation with higher strain rates promoted the division and fragmentation of alpha platelets during annealing. Transmission electron microscopy and X-ray diffraction analyses were employed to characterize dislocation components and structure, where the installed screw dislocations provided a fine substructure and high energy alpha/alpha boundaries in a platelets. The triple junction consisting of alpha/beta boundaries and alpha/alpha boundaries may provide a site for thermal grooving, which induces the division and fragmentation of a platelets. Therefore, deformation at a higher strain rate is necessary in alpha+beta processing to develop a fine equiaxed a microstructure for the Ti-10Al-1Zr-1Mo-1Nb alloy during annealing.