Microstructure and Mechanical Properties of In-situ Synthesized TiC and TiB Reinforced Titanium Matrix Composites

The different contents of in-situ synthesized TiC, TiB and TiC+TiB (volume proportion of 1:1)/Ti titanium matrix composites were prepared by vacuum consumable melting, forging and annealing process, and the microstructure, tensile properties at room temperature and high temperature (300℃) and compression properties at room temperature were studied. The coupling relationship between the strengthening effects of TiC and TiB during stretching at room temperature was analyzed. The results show that the matrix structure of composites was deformed α structure; TiC presented fine equiaxed shape and slightly thick ellipsoidal shape, and TiB presented short fiber shape. When the total volume fraction of reinforcements was fixed, the strengthening effect of TiC and TiB was higher than that of TiC or TiB, and increased with the increase of volume fraction of reinforcements; however, the plasticity of composites decreased obviously. The main tensile fracture mode of composites at room temperature was bearing failure of reinforcements, while the fracture mode at high temperature included bearing failure of reinforcements and debonding of some TiB short fibers with matrix. The relationship of strengthening effects between TiC and TiB reinforcements and fine-grain met the superposition of coupling coefficient of 1.5 during stretching at room temperature.