Microstructural Evolution and In Situ Formation of TiB and TiC in Ti─5Al─2.5Sn Alloy Processed by Powder Metallurgy

The incorporation of ceramic reinforcements into titanium alloys is widely explored to improve mechanical performance and expand application potential. This study investigates the in situ formation of TiB and TiC in a Ti–5Al–2.5Sn alloy with B ₄ C addition via powder metallurgy at different reinforcement contents and sintering temperatures. Thermodynamic calculations indicate an increase in the β ‐transus temperature and a reduction in the melting point with B ₄ C addition, suggesting the possible formation of a transient liquid phase during sintering. Differential scanning calorimetry reveals endothermic events associated with the melting of Al and Sn, followed by exothermic reactions at temperatures lower than those reported for comparable Ti–B ₄ C systems, suggesting enhanced diffusion during sintering. Phase formation is identified by X‐ray diffraction, while scanning electron microscopy and electron backscatter diffraction reveal TiB, limited TiC, and a predominantly α ‐Ti matrix. Porosity increases with reinforcement content and decreases with sintering temperature; however, hardness increases under both conditions. Overall, the combined thermodynamic, thermal, and microstructural results suggest that a transient liquid phase may have contributed to the earlier in situ formation of TiB and TiC and influenced the microstructural evolution of the composites.