Effect of TiN inclusion on the microstructure and mechanical property of TC4 titanium alloy

This study investigated the effect of TiN inclusion on the microstructure and compressive property of TC4 titanium alloy at room temperature through metallographic analysis and quasi-in-situ compression test. Moreover, the crack propagation mechanism during compression was analyzed. The results show that the test samples with internal TiN inclusion were fabricated by hot isostatic pressing. There weren’t any observable cracks, pores, or other defects in the diffusion zone between TiN inclusion and the TC4 titanium alloy. The microstructure of the diffusion zone with thickness 80 μm was composed of α phase, β phase, δ phase and ε phase. The yield strength of the TC4 alloy was affected slightly, but the fracture strength reduced significantly due to the TiN inclusion at room temperature. During compression, cracks initiated from the tiny defects inside the TiN inclusion and propagated rapidly. The multi-scale α phases in the diffusion zone caused the cracks to deflect, which promoted the initiation of secondary cracks, thereby effectively hindering crack propagation. As the compressive deformation increased, TiN underwent completely fractured, which leading to the fracture of TC4 alloy.