Simultaneously enhanced strength and corrosion resistance of Mg–3Al–1Zn alloy sheets with nano-grained surface layer produced by sliding friction treatment

Abstract

Simultaneous improvement of the two disparate properties such as mechanical strength and corrosion resistance of Mg alloys is the object researchers have been pursuing all the time. In this study, by means of sliding friction treatment (SFT), a nanocrystalline surface layer (with an average grain size of 70 nm on the topmost surface) was successfully generated on coarse-grained (CG, mean grain size: 25 μm) Mg–3Al–1Zn (AZ31) alloy sheet. The SFTed AZ31 exhibited simultaneously enhanced mechanical strength and corrosion resistance as compared to the CG counterpart. Specifically, the yield strength (YS) of SFTed sample is 236 MPa, which is almost twice that of CG sample (123 MPa). Meanwhile, the hydrogen evolution rate during 80 h immersion in 3.5% NaCl is reduced from 0.44 ml/cm2/h to 0.17 ml/cm2/h after SFT treatment. Effective grain refinement was responsible for the notable strength increment. The improvement in corrosion resistance might be correlated with SFT-induced grain refinement, good surface quality, second-phase particles fragmentation and strong basal texture. These combined capabilities of SFT render it a commercially viable manufacturing process for comprehensive properties modification of Mg products.