Characterization of hot deformation microstructures of alpha-beta titanium alloy with equiaxed structure

Abstract

Hot deformation behavior and microstructure evolution of TC11 (Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) alloy with equiaxed structure were investigated in the two-phase field at temperatures in the range of 980-800 °C and at strain rates of 0.001 s−1, 0.01 s−1, 0.1 s−1. Effects of thermo-mechanical parameters on both of the stress—strain curves and microstructure evolution were analyzed. Grain boundary characteristics of deformation microstructures were tested by electron backscattered diffraction (EBSD). The results reveal that β-phase dominates the deformation and presents discontinuous dynamic recrystallization at 980 °C; meanwhile, α-phase coarsens at lower strain rates and dissolves at higher strain rates, and α-phase volume fraction and grain size decrease with increasing strain rate. Super-plastic deformation occurs at 950-900 °C and strain rate of 0.001 s−1. And the deformation is dominated by soft β-phase, phase interfaces and grain boundaries. Microstructural mechanism operated at 850 °C is continuous dynamic recrystallization of α-phase that dominates the deformation, and β-phase deforms to match the deformation of α-phase.