Effect of Reinforcement Contents on Microstructure and Mechanical Properties of In-situ Synthesized Ti Matrix Composite 增强体含量对原位合成钛基复合材料微观组织及力学性能的影响

Four different kinds of TC18 Ti matrix composites containing trace amounts of TiB and TiC were fabricated by in-situ synthesis method. Results show that the merging of β grain is accelerated with increasing the reinforcements during heat treatment, and the standard deviations of β grain size distribution tend to decrease. The microstructure phenomenon is associated with the influence of the reinforcements on the boundary migration of β grains. The pinning ability of the reinforcements to the grain boundary migration decreases, which plays the most important role in the microstructure refinement. The plasticity of the composites is excellent during tensile test. However, when the molar ratio of TiB to TiC in the composites is 4:1, the yield ratios of the composites are all higher than 0. 96, and gradually increase with the increase of the reinforcements. The grain boundaries absorb the dislocations, which slows down the increase of dislocation strengthening during the strengthening process. It is suggested that the reinforcements accelerate the absorption of dislocations, and thus lead to this result. The contribution of the microstructure refinement to the toughness increases with the increase of reinforcements.