Microstructure and characterization of surface nanocrystallization of aluminum alloy

A nanostructured surface layer was fabricated on an aluminum alloy 1420 by using a high-energy shot peening (HESP) technique. HESP induced structure alone the depth of the treated sample surface layer was characterized by means of X-ray diffraction, transmission electron microscope and high-resolution electron microscope; and the hardness variation along the depth of the treated sample was examined. Experimental results show that nano-structured surface layer of about 20μm of thickness is formed after HESP, the average grain size increases from about 20 nm in the surface layer to about 100 nm at a depth of 20μm. In the region of 20-50μm deep from the surface, there exists submicro-fine grained layer. The degree of the surface crystallization is related to the amount of the plasticity deformation. The surface nanocrystallization can realize by the method of the plastic deformation of dislocation slipping. The hardness of nanostructured surface layer is enhanced significantly after HESP compared with that of the initial sample.