Microstructure and mechanical properties of B4C/TC4 titanium matrix composites produced by laser directed energy deposition

B4C/TC4 titanium matrix composites are fabricated by laser-directed energy deposition（L-DED） to investigate the effect of B4C content on the microstructure and mechanical properties of the deposited layers. The results indicate that during the deposited process，B4C reacts in-situ with the TC4 matrix，generating TiC and TiB reinforcement phases. With the addition of B4C content，the hardness of the composites increases significantly，while the plasticity decreases accordingly. When the mass fraction of B4C is 0.2%，the precipitated phases of TiC and TiB exhibit the most uniform distribution. At this point，the composite achieves the highest strength while still maintaining good plasticity，demonstrating the optimal comprehensive mechanical properties. This performance optimization is mainly attributed to the synergistic effect of multiple strengthening mechanisms，including the load transfer effect of TiB phases with a high aspect ratio，the pinning effect of precipitated phases on grain boundaries and the resulting grain refinement.