Laser powder bed fusion of Mo2C/Ti-6Al-4V composites with alternately laminated α′/β phases for enhanced mechanical properties

Abstract

Mo2C/Ti64 composites with nearly full densification and enhanced tensile strength were developed by using laser powder bed fusion (LPBF). The addition of 1–3 wt% Mo2C particles with an average particle size of ~ 1 µm enabled the LPBF-printed composites with an alternately laminated α′-Ti/β-Ti microstructure along with Mo2C and in-situ synthesized M23C6 (M was Ti, Al, V, and Mo). During LPBF, most of the Mo2C particles were incorporated into the Ti64 matrix, resulting in the α′-Ti and β-Ti solid solutions. The segregation of Mo contributed to the generation of the β-Ti phase at the melt pool boundaries of the composites, leading to the alternating hard α′-Ti/soft β-Ti phases. Remarkable improvements of 22.8% and 19.5% in the hardness and tensile strength of the Ti64 matrix were achieved, respectively. The strengthening of the LPBF-printed composites was associated with the formation of the laminated α′-Ti/β-Ti structure, solid solution behavior of Mo and C, and presence of the remaining Mo2C and precipitated M23C6. The findings are anticipated to provide insights into the selection of reinforcement materials for additively manufactured composites with nearly full densities and greater mechanical strength.