Effect of underwater friction stir processing on the microstructure, mechanical properties, and wear resistance of Al-9.2Si-4.9Cu-0.7Mg alloy

This research explores how rotational speed affects the microstructure, mechanical properties, and wear resistance of an Al-9.2Si-4.9Cu-0.7Mg alloy subjected to underwater friction stir processing. Analysis of the microstructure revealed a reduction in grain size from 4.4 ± 0.3 µm at 800 rpm to 2.3 ± 0.5 µm at 600 rpm. The tensile strength increased from 271.5 ± 11.3 MPa in the as-received material to 458.5 ± 13.1 MPa at 600 rpm, but dropped to 360.4 ± 12.2 MPa at 800 rpm. Elongation improved from 1.3 ± 0.2% in the base material to 3.7 ± 0.2% at 600 rpm and 4.2 ± 0.3% at 800 rpm. Significant improvements in wear resistance were observed, with wear rates decreasing from 6.9 ± 0.2 µg/m in the base material to 4.3 ± 0.3 µg/m at 600 rpm and 4.6 ± 0.1 µg/m at 800 rpm.