Tailoring grain size distribution for optimizing strength and ductility of multi-modal Zr

Abstract

In this study, multi-modal Zr metals composed of nano-grains (NG), ultrafine-grains (UFG) and micro-grains (CG) with various size distributions have been produced via cryorolling followed by thermal annealing. The strength of the multi-modal Zr consisting of UFG and CG follows approximately the rule-of-mixtures with the volume fraction of CG, while its ductility in the rolling direction deviates positively from the rule-of-mixtures. The 78% UFG+22% CG sample with a grain size distribution in the range of 200nm–1.6μm exhibits a good combination of high tensile strength (σb∼650MPa) and uniform elongation (εu∼13.4%), much better than that of CG Zr, σb∼350MPa and εu∼13.8%. The present study is significant for the enhancement of strength and ductility of engineering materials via the design of multi-scale structure.