Investigation into cooling-rate dependent residual stresses in ZrB₂–SiC composites using improved Raman spectroscopy method

Thermal residual stresses in spark-plasma sintered ZrB₂–20 vol% SiC composites were investigated for different cooling rates employed after sintering. A new method using barycenter shift of Raman emission band was developed to determine the surface residual stress in the SiC phase, with improved accuracy compared to measurements using the traditional peak shift method. Effect of cooling rate on thermal residual stress was quantitatively identified and analyzed. The results showed that the Raman spectroscopy method based on the barycenter shift can reduce the measurement scatter caused by small grain sizes and thus has better accuracy for ZrB₂–SiC composites with nano-sized SiC particles. It was found that a lower cooling rate reduced the average residual stress, which was attributed to the smaller thermal gradient, lower stain rate and more diffusional creep with reduction in cooling rate. In addition, decreasing grain size could also reduce the residual stress. This study provides an improved measurement method and a better understanding of the development and distribution of thermal residual stresses in ZrB₂–SiC composites.