Effect of FeCoNiCrMn addition on the Ti6Al4V alloy fabricated by spark plasma sintering and selected laser melting

Titanium matrix composites reinforced with high-entropy alloy (HEA) of FeCoNiCrMn particles were fabricated via spark plasma sintering (SPS) and selective laser melting (SLM) techniques. Effects of HEA contents on the microstructure and mechanical properties of Ti6Al4V (Ti64) alloy were comparatively investigated. Experimental results showed that some residue FeCoNiCrMn particles were existed in the Ti64 matrix and formed to be composite materials after SPS processing. There was a shell structure between the Ti64 matrix and the HEA particles, which was the element diffusion zone containing CrMn compounds. However, the HEA particles were completely solid dissolved into the Ti64 alloy, and β+ α´ dual-phase structure was formed after SLM processing. The optimal mechanical properties were achieved with 3.0 wt% HEA via SPS with an ultimate tensile strength (UTS) of 1139 MPa and 9.7 % ductility. SLM-processed Ti64/3.0HEA alloy achieved much higher properties, with a UTS of 1357 MPa and ductility of 10.9 %, attributed to dual-phase structure and TRIP effect. After heat-treatment, the SLM processed alloy showed enhanced ductility to 14.5 % with reduced strength. These findings highlighted the potential of FeCoNiCrMn particles as an effective reinforcement for titanium matrix composites, providing insights into the microstructural optimization for high-performance applications.