Ultrafine-grained surface layer on Mg–Al–Zn alloy produced by cryogenic burnishing for enhanced corrosion resistance

An ultrafine-grained surface layer was produced on Mg–Al–Zn alloy by a new severe plastic deformation process, cryogenic burnishing. The total burnishing-influenced zone was found to be over 3.4 mm thick. A large increase in hardness from 0.86 to 1.35 GPa was obtained near the topmost surface, where grains were refined from 12 μm down to 263 nm. The corrosion resistance was significantly enhanced, which may due to the combined effects of grain refinement and strong basal texture.