Influences of cold rolling, recrystallization and surface effect on the transformation textures in a TA10 titanium alloy

Abstract

Abstract A transformation treatment based on surface effect induced transformation is applied to cold rolled TA10 titanium alloy sheets to change and control transformation texture. This kind of treatment can promote the α-phase nucleation at sheet surface region during cooling and control the growth of surface α-grains into center layer of sheet. The results indicate that as the heating temperature increased, the transformation textures in the final HCP-structured TA10 sheets changed in helium atmosphere from the recrystallization type texture of <11-20>//RD to the transformation type texture of <11-20>//ND. The textures in sheets treated at low transformation temperature of 1000°C reveal texture memory effect, while those treated at high transformation temperature of 1100°C illustrate the effects of both transformation strain and anisotropy in elastic modules of HCP titanium crystals. The surface effect is promoted by cooling gas of helium, which leads to layered structures along sheet thickness direction. The surface region often shows small equiaxed grains with recrystallization orientations, while the center layer reveals coarse grains with either plate-like or equiaxed grain morphology corresponding to transformation orientation or recrystallization orientation, respectively. The special grain boundaries in plate-like α variants are different from those in equiaxed grains. These differences in morphologies, sizes and orientations are explained in terms of the mechanism change of the factors affecting variant selection.