Microstructural evolution and mechanical properties of SiC/2009Al composites under T6 heat treatment/high-frequency pulsed current treatment

30vol.% SiC/2009Al composites fabricated by powder metallurgy combined with hot extrusion technology were subjected to T6 heat treatment and high-frequency pulsed current treatment. The differences in microstructural evolution of the composites under these two conditions were analyzed, and the nano-mechanical behavior and tensile mechanical properties of the composites were tested.The results show that the internal grains of the as-extruded composites are severely elongated and deformed, with Al₂Cu and Mg₂Si precipitated phases dispersedly distributed inside. After shot peening deformation, the composite surface undergoes deformation while generating a certain number of microcracks. High dislocation density and strain hardening exist inside the shot-peened composites; after T6 heat treatment, partial static recovery occurs in the Al matrix region, and the proportion of low-angle grain boundaries decreases from 42.0% (shot-peened state) to 17.2%. After high-frequency pulsed current treatment, a higher proportion of static recovery and recrystallization occurs on the composite surface, and the proportion of low-angle grain boundaries decreases from 42.0% (shot-peened state) to 11.9%.The high-frequency skin effect and proximity effect effectively eliminate the macro/micro residual stress of the composites, and the KAM (Kernel Average Misorientation) value in the surface region decreases from 0.66 (shot-peened state) to 0.29. The tensile strength and elongation of the composites treated with 10000 Hz current reach 456 MPa and 19.5%, which are 38.6% and 29.14% higher than those of the shot-peened state, respectively. This confirms that high-frequency pulsed current treatment is a more excellent post-treatment strengthening technology.