Microstructural characterization and mechanical properties of (TiC+TiB)/TA15 composites prepared by an in-situ synthesis method

Titanium matrix composites reinforced with ceramic particles are considered a promising engineering material due to their combination of high specific strength, low density, and high modulus. In this study, the TA15-based composites reinforced with a volume fraction of 10% to 25% (TiB+TiC) were prepared using powder metallurgy and casting technique. Microstructural characterization and phase constitution were examined using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In addition, the microhardness, room temperature (RT) and high temperature (HT) tensile properties of the composites were evaluated. Results revealed that the reinforcements are distributed uniformly even in the composites with a high volume of TiB and TiC. However, as the volume fraction exceeds 15%, TiB and TiC particles become coarsening and exhibit rod-like and dendritic-like morphology. Microhardness increases gradually from 321.2 HV for the base alloy to a maximum of 473.3 HV as the reinforcement increases to 25vol.%. Tensile test results indicate that a reinforcement volume fraction above 20% is beneficial for enhancing tensile strength and yield strength at high temperatures, but it has an adverse effect on room temperature elongation. Conversely, if the reinforcement volume fraction is below 20%, it can improve high-temperature elongation when the temperature exceeds 600 °C.