Microstructure and mechanical properties of laser melting deposited (TiB+TiC)/TA15 in situ titanium matrix composites

(TiB+TiC)/TA15 in situ titanium matrix composites with 9%，11%，22% and  57% volume fractions of TiB+TiC reinforcements, respectively were fabricated by the laser melting deposition manufacturing process. The morphology of TiB changes from plate-like to prismatic while the morphology of TiC evolves from particle-like to dendritic with the increasing volume fraction of the reinforcements. The Rockwell hardness and elastic modulus of the composites increase and the ductility decreases with the increasing volume fraction of TiB+TiC reinforcements. The composite with a reinforcement volume fraction of 9% exhibits the optimum mechanical properties，while the tensile strength of the composites decreases abruptly when the reinforcement volume fraction is up to approximately 11%. The yield strength (935 MPa) and ultimate tensile strength (1040 MPa) of the laser melting deposited in situ (TiB+TiC)/TA15 composite containing 9% volume fraction of TiB+TiC reinforcements are both enhanced by 12% compared to the as-laser deposited titanium alloy TA15.