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The welding tool geometry plays a critical role in acquiring desired microstructures and the heat-affected zones, and consequently improving the strength of the joint in friction stir welding. In this study, a friction stir welding process with different tool pin and shoulder diameter was numerically modeled. A thermomechanically coupled, 3D FEM analysis was used to investigate the effect of tool pin and shoulder diameter on welding force, material flow, thermal, and strain distributions in AA5083 aluminum alloy. Then, an artificial neural network model was employed to model the correlation between the tool parameters (pin and shoulder diameter) and heat-affected zone, thermal, and strain value in the weld zone.

In this research, nanosized SiC and Al 2 O 3 particles were added to as-cast AZ91 magnesium alloy, and surface nanocomposite layers with ultrafine-grained structure were produced via friction stir processing (FSP). Effects of reinforcing particle types and FSP pass number on the powder distribution pattern, microstructure, microhardness, and on tensile and wear properties of the developed surfaces were investigated. Results show that the created nanocomposite layer by SiC particles exhibits a microstructure with smaller grains and higher hardness, strength, and elongation compared to the layer by Al 2 O 3 particles. SiC particles do not stick together and are distributed separately in the AZ91 matrix; however, distribution of SiC particles is not uniform in all parts of the stirred zone (SZ), which causes heterogeneity in microstructure, hardness, and wear mechanism of the layer. Al 2 O 3 particles are agglomerated in the different points of matrix and create alumina clusters. However, distribution of Al 2 O 3 clusters in all parts of the SZ is uniform and results in a uniform microstructure. In the specimen produced by one-pass FSP and SiC particles, the wear mechanism changes in different zones of SZ due to the nonuniform distribution of particles. However, in the specimen produced by Al 2 O 3 particles, the wear mechanism in all parts of the SZ is the same and, in addition to the abrasive wear, delamination also occurs. Increasing FSP pass number results in improved distribution of particles, finer grains, and higher hardness, strength, elongation, and wear resistance.

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