Ultrafine-Grained Surface Layer Formation of Aluminum Alloy 5083 by Friction Stir Processing

Friction stir processing experiments are conducted on aluminum alloy 5083 plates to enhance the surface integrity by introducing an ultrafine-grained surface layer. Microstructural analyses are carried out using optical microscopy to characterize the grain structures under various conditions. Within the produced surface layer, equiaxed ultra-fine grains are observed due to dynamic recrystallized during FSP. The grain size is reduced from 40 μm to a submicron level for the FSP rotational speed of 800 rpm. The hardness is increased to a peak value of 151 HV, which is higher than that of the unprocessed area by 50%.