Impact of ECAP at 300 °C on the microstructure and mechanical properties of the quenched Zr–2.5%Nb alloy

Abstract

We investigated the microstructure of the Zr–2.5%Nb zirconium alloy after subjecting it to equal-channel angular pressing (ECAP) and found that ECAP at 300 °C increases the strength by 140 to 180 %. Notably, unlike other studies, our alloy did not show complete dissolution of niobium particles, which may be due to the reduced diffusion rates at the lower deformation temperature of 300 °C. Pre-treatment involving quenching before severe plastic deformation was also studied, which developed a lamellar structure introducing additional boundaries that facilitated grain refinement during subsequent ECAP. The strength of the alloy was further enhanced by solid-solution hardening, achieved through the complete dissolution of the Nb particles into the matrix post-quenching. This process resulted in a 2.3-fold increase in yield strength after quenching plus ECAP compared to the initial coarse-grained state.