Designing strong and ductile heterogeneous lamella-structured Mg alloy via diffusion bonding

Abstract

Achieving superior strength-ductility synergy in Mg alloys is a critical issue for engineering applications. To address the trade-off between strength and ductility, the introduction of heterogeneous lamellar structures has recently proven be an effective strategy. In this study, we fabricated an AZ31/WE43/AZ31 alloy with heterogeneous lamellar structure using diffusion bonding (DB). Increasing the DB temperature enhanced the diffusion behavior, resulting in the precipitation and growth of Al2(Y, Nd) phases within the interfacial diffusion zone. Additionally, grain growth occurred, leading to a reduction in the heterogeneity of the grain size in individual AZ31 and WE43 layers. The sample fabricated at 460 °C, which exhibited relatively high heterogeneity and strong interfacial bonding, demonstrated a good combination of yield strength (202.4 MPa), ultimate tensile strength (315.8 MPa), and elongation (19.4 %). These mechanical properties significantly surpassed those of the original individual materials and exceeded the rule-of-mixture predictions. The excellent strength-ductility synergy observed in this alloy can be attributed to the presence of heterogeneous deformation-induced stress (HDI stress), which promotes extensive activation of non-basal dislocation slips. Furthermore, in-situ tensile tests demonstrated that the pile-up of geometrically necessary dislocations (GNDs) at the heterogeneous interface contributed to the superior HDI strengthening and HDI strain hardening. Overall, this study provides new insights into the fabrication of heterogeneous lamella-structured Mg alloys with strength-ductility synergy.