Microstructure, creep behavior and corrosion resistance in the ultrafine-grained surface layer of Mg-6Zn-0.2Y-0.4Ce-0.5Zr alloy processed by surfacing friction treatment

Gradient Mg-6Zn-0.2Y-0.4Ce-0.5Zr alloy sheet, with a nanocrystalline surface layer of 98 nm on the topmost surface, was prepared by sliding friction treatment (SFT). Nanoindentation test used to research the influence of grain refinement on the creep behavior and corresponding deformation behaviors under different range of loading strain rates. It is shown that nano-grained layer exhibits a long creep distance but a peaceful creep behavior, which is mainly attributed to the abundant plastic deformation behaviors after nanocrystallization. The corrosion behavior of SFTed layer and un-SFTed layer was investigated by electrochemical tests and hydrogen evolution in 3.5% solution. The corrosion resistance is improved in the nano-grained layer by the reduction of grain size which promotes the formation of passive film and the rearrangement of second-phase particles which suppresses the corrosion rate. SFT method is an effective way in refining grain size while improving the corrosion resistance.