Nanocrystalline structure of magnesium alloys subjected to high energy shot peening

At present methods of high energy shot peening (HESP), one of the severe plastic deformation (SPD) has been used to process ultrafine-grained (UFG) (nano- and submicrocrystalline) materials. It has been found that during SPD of AZ91 magnesium alloy the structure of the surface layer develops from a cell structure to a fragmented structure with high angle misorientations and a mean grain size of 40 nm. According to X-ray and transmission electron microscopy data, the nanostructure is the single phase which is the supersaturated solid solution by β-phases re-dissolution in Mg matrix. Fast diffusion during deformation is conditioned by the high stresses acting on the grain boundaries and the volumes of the fine grains. During deformation of the nanocrystalline the volume diffusion coefficient is equal to about Dv = 2.2 × 10−15 cm2/s.