Substructure and texture evolution and flow behavior of TA15 titanium alloy compressed in the alpha + beta two-phase field

This paper investigates the substructure and texture evolution of a near-α titanium alloy Ti–6Al–2Zr–1Mo–1V (TA15) during isothermal hot compression in an α + β two-phase field. The microstructures of deformed samples were analyzed using an electron backscatter diffraction (EBSD) technique to study the effects of process parameters on the evolution of substructure and texture. The activated energy and the stress exponent were calculated to identify the deformation behaviors and the softening mechanisms. The experimental results showed that the transformation of low angle boundaries (LABs) to high angle boundaries (HABs) was sensitive to strain rate, strain and temperature. The volume fraction of the HABs increased with the increasing strain rate or strain but decreased with increasing temperature. During the transformation process, the dislocations inside the subgrains and around the subgrain boundaries were annihilated by dislocation reaction and absorption. The transformation of the LABs into HABs significantly influenced the flow stress during the thermomechanical processing. With the increase of strain or temperature, the texture in the alpha phase became weaker and the pyramidal slip systems began to be activated, while the texture in the beta phase tended to be stronger with more plastic deformation.