Microstructure and mechanical properties of TiC/Ti6Al4V composite fabricated by concurrent wire-powder feeding laser-directed energy deposition

Abstract

Laser-directed energy deposition concurrent wire-powder feeding (L-DED-WP) combines the advantages of wire-feeding and powder-feeding laser deposition, offering a novel method for fabricating metal matrix composites at a lower cost and higher efficiency. This work successfully produced defect-free Ti6Al4V alloy and TiC/Ti6Al4V composites using wire-feeding laser deposition and L-DED-WP, respectively. L-DED-WP process was achieved by lateral feeding of Ti6Al4V wire and coaxial feeding of TiC particles, with an additional TiC content of 2.93 wt%. The microstructure characteristics and mechanical performance of Ti6Al4V alloy and TiC/Ti6Al4V composites were analysed. The results indicate that after adding TiC particles, the in-situ eutectic-TiC precipitated in the matrix. Due to the uneven distribution of TiC particles along the build direction during solidification, the quantity of eutectic-TiC gradually increased from the bottom to the middle and top regions of the deposition layer. Correspondingly, the morphology of eutectic-TiC was granular at the bottom, short rod-like in the middle, and a mix of both granular and short rod-like in the top region. Additionally, the eutectic-TiC served as heterogeneous nucleation sites, promoting the refinement and inhibiting the growth of α-Ti, resulting in a decreased aspect ratio of α-Ti and texture strength. Compared to Ti6Al4V, the yield strength of TiC/Ti6Al4V increased by 11.19 %, while the tensile strength improved by 11.46 %. However, during the tensile testing, the non-uniformly distributed brittle eutectic-TiC could only release stress by fracturing, resulting in a 2.57 % decrease in elongation.