Numerical Analysis of the Effects of Reinforcing Particles on the Residual Stress of TiB₂/Al-Si Composites Fabricated by Laser Powder Bed Fusion

Large temperature gradient will produce high residual stress during laser powder bed fusion (LPBF). In metal matrix composites (MMCs), the thermal-induced stress distributes complexly. It is indispensable to study the interfacial stress of MMCs during LPBF process. In this study, a multi-phase finite element model was established to reveal the temperature and stress distributions of TiB₂/Al-Si composites fabricated by LPBF. Influences of particulate geometries on the residual stress were also analyzed in the model. The numerical results indicate that the residual stress in the composites was induced by high temperature gradient and coefficient of thermal expansion mismatch simultaneously. TiB₂ reinforcing particles suffer large compressive stress perpendicular to the interface. In the matrix, the stress component at the interface is negative and increases rapidly with distance from the particle increases. The interfacial compressive stress lessens the mean tension stress in the nearby regions of the matrix. Maximum von Mises stress is generated at the interface in the matrix, which may cause defects and cracks. High interfacial stress was generated in the vicinity of the vertex of cubic particles and the internal stress large in ellipsoidal particles, indicating that particles with fewer edges and smaller slenderness ratio possess greater thermal shock resistance.