Insight into microstructure evolution and mechanical properties of 5 wt% SiC/Al composites by high frequency pulse current treatment

Abstract

In order to improve the status of stress concentration and anisotropy of the as-rolled SiC/Al composites, high frequency pulse current was employed to modify the microstructure and mechanical property. Results show that the skin effect makes the current concentrate on the surface zone. The high density current makes the static recrystallization of 35.8% occurred under the condition that the surface temperature is much lower than that of recrystallization temperature of Al alloy, and the grain size is refined from 2.52 μm to 2.06 μm. The obvious recrystallization behavior in the surface area indicates that the non-thermal effect plays a dominant role in the pulse current treatment process. As a contrast, subgrains growth and partial recrystallization occurred in the internal region and transition region under the non-thermal effect, resulting in a slight increase in average grain size to 2.78 μm and 2.75 μm. Nano-indentation results show that the micro-hardness and the indention work recovery rate in the surface area reach 2.09 GPa and 39.8%, respectively, which are 48.2% and 29.2% higher than that of the as-rolled composites, which proves that the mechanical properties have been improved comprehensively compared with as-rolled composites.