Thermal mismatch stress relaxation and dislocation transformation of 45%SiCp/Al composites by continuous diode laser heating

Abstract

The purpose of the study was to investigate the effect of laser beam scanning on residual stress relaxation and metallographic structure evolution of 45%SiCp/Al composites with an increase in the temperature. Based on the theory of elasticity and equivalent inclusions, the residual stresses distribution of individual component in 45%SiCp/Al composites with an increase in the temperature are obtained. The results demonstrated that the speed of stress relaxation for matrix and interface was faster with the temperature variation from 25 to 300 °C comparing with the temperature variation from 300 to 500 °C. The dislocation configurations and morphologies of second precipitated phases with laser treatment were characterized using the optical microscopy and transmission electron microscopy. It is found that the thermal residual stress relaxation mechanism with an increase in the temperature was caused due to the evolution of dislocation density and dislocation structure arrangements. A physical model of dislocation and grain evolutionary process with an increase in the temperature was proposed, and the effects of laser scanning on precipitated phase was analyzed in view of the interaction mechanism between the mobile dislocations and the precipitated phase. The nanoindentation test was also carried out to analyse the effect of residual stress and dislocations configuration on the mechanical response of individual component.