Microstructure and Residual Stress of In-situ Synthesized (TiC+TiB)/Ti Composites

(TiC+TiB)/Ti composites with different reinforcement (TiC, TiB) content were prepared by in-situ synthesis of Ti, graphite and TiB₂ followed by vacuum melting,forging and annealing. The phase composition and microstructure were studied and the residual stresses were measured. Numerical simulation formulas of residual stresses were also established to analyze the coupling relationship between micro residual stresses. The results show that the Ti substrate in Ti matrix composites was composed of deformed α-microstructure and the reinforcements dispersed evenly. TiC had equiaxed or irregular shapes while TiB was short fibrous and distributed along forging direction. Mirco residual stresses generated by the mismatch of coefficients of thermal expansion between TiC or TiB and Ti substrate were tension and compression stresses, respectively. When the volume ratio of TiC to TiB was 1:1, the coupling coefficient of the micro residual stresses was 2.0.