A novel strategy synergistically enhances the strength and ductility of Mg-Gd-Zr alloys by tailoring a heterogeneous structure

Abstract

We introduced an innovative methodology employing the high shearing dispersion technique (HSDT) to uniformly distribute Zr particles, creating a heterogeneous structure with more and finer fine-grained regions after extrusion, which enhanced the strength and ductility synergistically in Mg-3Gd-1Zr (VK31) alloys. Compared to non-high sheared VK31 (NHS-VK31) alloy, the high sheared VK31 (HS-VK31) alloy exhibited a 30 MPa increase in yield strength and a 7.9 % improvement in elongation. HSDT applied before solidification effectively dispersed and refined Zr particles, suppressed dynamic recrystallization nucleation and growth during extrusion, which contributing to the development of heterogeneous structures. The finer average grain size of the HS-VK31 alloy (3.64 μm) was a key factor in the strength increase compared to the NHS-VK31 alloy (8.09 μm). During deformation of the HS-VK31 alloy, the more numerous and finer grains in fine-grained regions created favorable conditions for the activation of <c+a> dislocations, which were easily decomposed into partial dislocations (<c> dislocations and <a> dislocations) and stacking faults. The activation of high-density non-basal dislocations and stacking faults in the fine-grained zones was primarily responsible for the improvement of ductility. Additionally, the more dispersed and finer Zr particles in HS-VK31 alloy could effectively alleviate stress concentration, preventing the deterioration of ductility. This work presented an advanced design paradigm for heterogeneous structures, providing novel insights and perspectives for the evolution of strength-ductility synergy in alloy development.