Microstructure and mechanical properties of in-situ Ti5Si3/TC4 composites via spark plasma sintering and hot rolling

In this study, low energy ball milling and spark plasma sintering techniques prepared the in-situ synthesized Ti5Si3 reinforced Ti-6Al-4V (TC4) matrix composites and then rolled them at high temperatures. In the composites with high Si content, the Ti5Si3 particles distributed at the interface of alpha-phase and 8-phase agglomerated and then formed a quasi-continuous network structure, which will deteriorate the plasticity of the composites. After hot rolling, the grains of the composite were significantly refined, and more Ti5Si3 particles were precipitated. With the increase in Si content, the tensile strength of sintered composites increased slightly, but the elongation decreased greatly. After hot rolling, the tensile strength of the composite increased significantly with an increment of 359.4 MPa, among which the composite with 0.6 wt% Si achieved a synchronous increase in strength and plasticity. The strengthening mechanism of sintered composites included dislocation strengthening, solution strengthening, and grain refinement, among which dislocation strengthening and grain refinement were the main strengthening mechanisms. The strengthening mechanism of rolled composites was mainly the dislocation strengthening caused by rolling, the grain refinement, and the mismatch of thermal expansion coefficient.