Achieving extraordinary thermal stability of fine-grained structure in a dilute magnesium alloy

Abstract

High-temperature solid-solution is indispensable for bake-hardenable dilute Mg alloys, which generally induces grain coarsening. Herein, we report extraordinary thermal stability in a bake-hardenable dilute Mg-1.61Zn-0.57Mn-0.54Ca-0.46Al (wt. %, ZMXA2110) alloy, maintaining fine-grained structure at 450 °C. The thermal stability is stemmed from the Zener pinning effect of dense fine (∼15.0 nm) core–shell β-Mn particles and co-segregation of Zn and Ca at grain boundaries. The fine-grained (∼3.2 μm) dilute alloy exhibits high room-temperature formability in solid-solution condition with an Index Erichsen value of ∼6.0 mm, and impressive yield strength of ∼293 MPa with an evident increment of ∼60 MPa by bake-hardening treatment.