Achieving superior high-temperature performance in Ti60 alloy with dispersed TiC reinforcement via directed energy deposition

Abstract

Addition of reinforcing particle is a potential strategy to counteract the significant strength degradation of titanium alloys at their maximum service temperature of 600 °C. However, a long-standing challenge for particle-reinforced titanium matrix composites is their poor ductility and limited formability. In this work, directed energy deposition (DED) was employed to fabricate Ti60 alloy with dispersed TiC particles, using carbon-decorated C/Ti60 composite powders as feedstock. The reinforced TiC particles, with a volume fraction of approximately 9.8 %, consist of submicron TiC span across multiple α laths and nanoscale TiC particles within α laths. Due to the introduction of TiC particles, the average width of α phase has decreased from 1.18 μm to 0.92 μm. The TiC particles significantly enhance the high-temperature strength of the Ti60 alloy by 11.7 %, 11.0 %, and 10.6 % at 600 °C, 650 °C, and 700 °C, respectively, through a combination of Orowan strengthening, grain refinement and solid solution strengthening mechanisms, while retaining excellent elongation of 16.3 %, 42.3 % and 47.1 %. Additionally, the nanoscale TiC particles form coherent interfaces within the matrix, resulting in lattice distortions that increase the proportion of low-angle grain boundaries. This phenomenon can provide sufficient driving force for the early triggering of the Dynamic recrystallization (DRX) process, resulting in a lower recrystallization temperature in the TiC/Ti60 composites compared to the Ti60 alloy. This work represents a significant advancement in overcoming the trade-off between strength and ductility in particle-reinforced titanium matrix composites and offers a promising avenue for the next generation of high-temperature light alloys.