Pre-strain me diate d fast natural aging in a dilute Mg-Zn-Ca-Sn-Mn alloy

A remarkable natural aging (NA) hardening response induced by pre-strain treatment, i.e. an evident increment of flow stress from-138 MPa to-163 MPa within only 48h, was observed in a dilute Mg-1.0Zn- 0.45Ca-0.33Sn-0.2Mn (wt.%, ZXTM10 0 0) alloy sheet. The pre-strain deformation introduces profuse basal < a > dislocations and supersaturated non-equilibrium vacancies, favoring the solute diffusion process and therefore resulting in a heterogeneous solute distribution for energy minimization. The retarded dislocation movement by co-segregation of Zn and Ca atoms is responsible for the strengthening effect. This work sheds light on the appreciable NA phenomenon previously unexpected in dilute Mg alloys assisted by the introduction of crystal defects, and the associated microstructure evolutions at ambient temperature provide a novel strategy for the design of high-performance low-cost Mg alloys. (c) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.