Overall optimization in microstructure and mechanical properties of 5 wt% SiC/7075Al composites by high-frequency electric pulse assisted treatment

Abstract

The microstructure evolution and mechanical properties of 5 wt% SiC/7075Al composites processed with a combination of three-step spark plasma sintering (SPS), hot rolling (HR), and high-frequency electric pulse assisted treatment (HEAT) processing were investigated herein. It was found that the HEAT tremendously promoted the recrystallization behavior after the hot rolling, leading to grain refinement and residual stress weakening. It can be attributed to the combination of the electrical (Electron wind) and thermal effects (Joule heat) of pulse current. Electron wind promotes the expansion of the movement of dislocations, providing the material basis for recrystallization. Joule heat and residual stress within the matrix provide the substance conditions. There was a remarkable improvement in strength and ductility, among which the increase in strength was mainly due to the combined effect of phase precipitation strengthening and grain refinement, while the increase in elongation was mainly attributed to grain refinement and residual stress weakening. Compared to those of the untreated samples, the average grain size decreased by 18.3%, residual stresses reduced by 70%, and tensile strength improved by 37.3%. High-frequency assisted treatment has a comprehensive improvement on the microstructure and mechanical properties of SiC/7075Al composites.

Keywords

• SiC/7075Al composites
• High-frequency electric pulse assisted treatment
• Grain refinement
• Residual stress weakening