A bake-hardenable Mg-Zn-Sn-Ca alloy addressing strength-corrosion trade-off via solute segregation to dislocations

Abstract

Increasing dislocation density is conducive to improving strength of Mg alloys, while the corrosion resistance would be considerably compromised because high-energy dislocations preferentially suffer severe corrosion. Herein, an appreciable flow stress increment of ∼43 MPa (from ∼191 MPa to ∼234 MPa) with no sacrifice of corrosion resistance could be achieved in solutioned Mg-2Zn-1Sn-0.5Ca (wt.%, ZTX210) alloy after 2 % pre-stretch and aging treatment. Even though introducing higher density of dislocations after 5 % pre-stretch, the aged alloy does not show deterioration in corrosion resistance compared to the solutioned counterpart. The reduced elastic strain energy around basal 〈a〉 dislocation cores by co-segregation of Zn, Ca and Sn atoms accounts for the inhibited adverse effect of dislocations on corrosion resistance. The solute co-segregation could also pin dislocation motion, thereby endowing alloy with excellent bake-hardenability. This work would provide new insights to fabricate strong and anti-corrosive Mg alloys.