Research progress in nanocrystalline microstructure, mechanical properties and nanocrystallization mechanism of titanium alloys via surface mechanical treatment

Local severe plastic deformation via mechanical treatment is the main method for surface nanocrystallization of titanium alloys. The methods mainly include surface mechanical attrition, supersonic fine particles bombarding, high energy shot peening and laser shock peening. Nanostructured surface layer could be synthesized by controlling the processing parameters, and the microstructure gradually changes from nanocrystalline structure to the coarse grains in the base alloy along depth direction. The nonstructural surface layer increases the strength, hardness and corrosion resistance of titanium alloys evidently. The surface nanocrystallization mechanism of titanium alloys mainly depends on the content of α and β phases. The twin intersection mechanism dominate that the refinement in titanium alloys mainly consists of α phase, while the refinement in titanium alloys mainly consisting of β phase was induced by dislocation intersection instead. The investigation prospects of the surface nanocrystallization of titanium alloys via mechanical treatment were proposed on the basis of current status.