Effect of rate on the deformation properties of metastable β in a high Sn content zirconium alloy

The quaternary zirconium alloy, Zr-3.5Sn-0.8Mo-0.8Nb, has shown promise as a possible system for utilization of transformation-induced plasticity. In this study, we investigate the effect of strain rate and stress-relaxation on the beta -> alpha phase transformation at room temperature, and present a technique to characterize the thermally-activated deformation of component phases of multi-phase alloys. The apparent activation volume of the a phase of this alloy is 13-18b(3), in agreement with previous studies on a-zirconium alloys, while the beta phase has an apparent activation volume of 80-150b(3). The deformation-induced phase transformation is observed to occur more readily at lower strain rates, due to a higher strain-rate dependence than dislocation slip. This effect may lead to enhanced resistance to necking in this alloy during forming operations.