Abstract
Surface Mechanical Attrition Treatment (SMAT) is one of the processes used to improve surface properties. In the present study, the effect of process parameters such as the diameter and number of shots, working height, and SMAT time on the residual stresses and the mechanical properties of the AZ31 magnesium alloy surface is investigated. This analysis was performed using Minitab software, experimental tests, Taguchi test design (array L9), and signal-to-noise analysis. In this research, investigating the microstructure using a scanning electron microscope (SEM), determining the phases and crystal structure using an X-ray diffraction (XRD) pattern, measuring the hardness of the samples using the Vickers method, and evaluating the wear behavior of the samples using the wear test method by peening on the disc were considered. Samples 1 and 3 had the minimum and maximum mass reduction, accompanied by a 32 and 57 % increase in wear resistance compared to the raw sample. By performing the SMAT process during the L9 experiments, the nanocrystallization of the grains caused a 35 and 46 % increase in the hardness of samples 1 and 3 with minimum and maximum hardness, and as a result, an increase of 32 and 57 % in wear resistance was seen compared to the raw sample. According to the results, time was considered the most important parameter of the process, and it affected the residual stress, surface hardness, and wear resistance by 63 and 64 %, respectively. This relates to the fineness of the grains on the surface and the microstrains created by the SMAT process.

Key words
AZ31 alloy, surface mechanical attrition treatment, Taguchi approach, microstructures, compressive residual stress, hardness, roughness, wear resistance

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