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In current research, the effect of the multi-directional forging (MDF) process on the microstructure, texture, mechanical and electrical properties of AA-6063 under different heat treatment conditions at various MDF temperatures was studied. The annealed AA-6063 alloy was processed up to three passes of MDF at ambient temperature. Three passes of this process were also applied to the solution-treated AA-6063 at ambient temperature and 177 °C. Microstructural investigations demonstrated that the MDF process led to a significant reduction in the average grain size as well as a considerable increase in the fraction of low angle grain boundaries. Texture analysis revealed that copper and Goss textures were mainly developed within the annealed and solution-treated samples of AA-6063, respectively. The hardness and shear strength values of all processed samples also showed a sizeable improvement compared to the initial heat-treated samples. For example, the hardness and shear yield strength value of the solution-treated sample MDFed for three passes showed more than 100 and 70% increase, respectively. The effect of the MDF process on the electrical conductivity of AA-6063 under different heat treatment conditions at various temperatures was negligible. So, it can be concluded that the MDF process increased the mechanical properties without an appreciable decrease in electrical conductivity.

This study was undertaken with the aim of modifying the microstructure and improving the tribological properties of in situ Al-20Mg2Si composite. For this purpose, friction stir processing (FSP) was applied on the composite at constant travel and rotation speeds of 110 mm/min and 1500 rpm, respectively, using three different tool pin profiles: threaded tapered cylindrical, triangular tapered, and triangular threaded tapered. The sliding wear tests were conducted using a pin-on-disc apparatus under the applied load of 30 N and sliding distance of 1000 m at room temperature. The results showed that FSP substantially improved tribological properties of the as-cast composite. The best result was observed in the sample processed by the threaded triangular tapered tool, where compared with the as-cast composite, its wear rate and average friction coefficient decreased by almost 40% and 18%, respectively. This improvement can be attributed to the significant refinement and uniform redistribution of Mg2Si intermetallics, especially the coarse irregular-shaped primary crystals, the formation of ultrafine grains, and elimination of casting defects from the substrate microstructure of the processed sample, which improves its hardness and increased its potential in supporting the oxide tribolayer on the composite surface.

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