Evolution of residual stress of SiCf/Ti17 composites at high temperature evaluated by micro-Raman spectroscopy

Abstract

SiC_f/Ti17 composites are considered promising lightweight high-temperature structural materials for the aerospace field due to their excellent mechanical properties. However, during the manufacturing process, differences in the coefficients of thermal expansion between various material components inevitably generate thermal residual stresses at the interfaces. These thermal residual stresses can lead to stress concentration and other failure modes, thereby affecting the mechanical properties of SiC_f/Ti17 composites. Therefore, it is crucial to systematically study the residual stresses in the interfacial C coating and the W/SiC interfacial regions, as well as the evolution of these stresses at high temperatures. In this study, samples were first subjected to vacuum heat treatment, followed by systematic micro-Raman experiments conducted radially on the fibers. Subsequently, the Raman spectra were subjected to peak deconvolution to obtain precise target peaks. By combining Raman peak shifts with Hooke's law, the evolution of high temperature residual stresses in the C coating and W/SiC interfacial regions were determined. Additionally, changes in the Raman spectral data at different temperatures were analyzed to investigate the variations in the micro-composition of different regions. The results showed that at 850 °C, both the C coating and the W/SiC interfacial region exhibited good mechanical properties and strength retention. However, at 1050 °C, the mechanical properties of both regions gradually deteriorated, with the W/SiC interfacial region showing a sharp increase in compressive stress. At this point, the SiC_f/Ti17 composite material may face a risk of failure.