Experimental Analysis on the Material Properties of A356.0 Aluminum Alloy Surface Nanostructured by Severe Shot Peening

Abstract

The effects of severe shot-peening process and formation of a nanostructured surface layer on mechanical properties of A356.0 alloy were investigated in this paper. X-ray diffraction analyses revealed that the average size of near-surface grains in severe shot-peened specimens is 75.8 nm. Three types of disk-shaped specimens, non-treated, conventionally shot-peened, and severely shot-peened were subjected to pin-on-disk wear test in the dry condition, in different loading and sliding speeds. Shot-peening process increases both hardness and roughness of the surface, and these two factors have, respectively, positive and negative effects on wear resistance. However, because of high-density grain boundaries in severe shot-peened specimens, the effect of increased hardness overcomes the effect of increased roughness. As a result, the wear resistance of severely shot-peened specimens is higher than the others. Wear tracks were characterized by scanning electron microscopy. By changing the normal load from 5 to 10 N, the wear regime alters from mild to severe. Morphology of the specimens illustrated that the predominant wear mechanism in the mild regime and the severe regime are, respectively, oxidation and abrasive. Experimental results also showed that severe shot-peening procedure improves hardness, yield strength, and fracture toughness up to 52, 16, and 49%, respectively.