Microstructure evolution and mechanical properties of an Mg-Gd alloy subjected to surface mechanical attrition treatment

Nanometer-sized grains (around 50-100 nm) were generated in the surface layer (0-30 μm) of an Mg-3Gd alloy by means of surface mechanical attrition treatment (SMAT) at room temperature. The deformation process and the formation mechanism of nano grains were investigated by using transmission electron microscopy. The results show that twinning dominates the initial stage of the plastic deformation when the dislocation slips are obstructed. And till all the coarse grains are divided into substructures by twin-twin interactions and twin-dislocation arrays intersections, dislocation slips and stacking faults begin to play an important role in impelling subgrains to nanograins by lattice rotating through dislocation arrays slipping. Dynamic rotation recrystallization is the primarily formation mechanism of the nanocrystalline of Mg-3Gd alloy by SMAT, which is distinct from the migration recrystallization normally observed in severe plastic deformation process.