Effect of initial grain size on the hot deformation behavior of 47Zr-45Ti-5Al-3V alloy

The effect of initial grain size on the hot deformation behavior of the 47Zr-45Ti-5Al-3V (wt.%) alloy was investigated by compression tests. 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 for the coarse-grained alloy was higher than that for the fine-grained alloy. A hyperbolic-sine Arrhenius-type equation was used to characterize the dependence of the flow stress on deformation temperature and strain rate. The flow stress for the coarse-grained alloy was higher than that for the fine-grained alloy at a given deformation temperature and strain rate. The activation energy of deformation decreased gradually with increasing strain, and at strains larger than 0.1 the activation energy for the fine-grained alloy was higher than that for the coarse-grained alloy. The processing maps for hot working at different strains were obtained. Fine initial grains reduced the flow instability and decreased the deformation temperature for the optimum hot working condition.