Hot deformation behavior of Ti–20Zr–6.5Al–4V alloy in the α+β and single β phase field

Abstract

The hot deformation behavior of Ti–20Zr–6.5Al–4V alloy in the α+β and single β phase field was investigated by compression tests in the temperature range of 800–1050°C and strain rate range of 10−3–100s−1. At low temperatures and high strain rates, the flow curves exhibited a pronounced stress drop at the very beginning of deformation, followed by a slow decrease in flow stress with increasing strain. The magnitude of the stress drop increased with decreasing deformation temperature and increasing strain rate. At high temperatures and low strain rates, the flow curves exhibited typical characteristics of dynamic recrystallization. A hyperbolic-sine Arrhenius-type equation was used to characterize the dependence of the flow stress on deformation temperature and strain rate. The activation energy of deformation in the α+β phase field decreased from 375.5 to 174.3kJ/mol with increasing strain, while it decreased from 220.6 to 172.5kJ/mol in the single β phase field. The processing maps for hot working at different strains were constructed. The optimum processing window was determined to be in the strain rate range of 7.4×10−3–1.2×10−1s−1 and temperature range of 895–1020°C.