Evaluation of microstructure and mechanical performance of spark plasma sintered TiAl alloy reinforced with Si3N4 and TiCN additives

Abstract This work evaluates the microstructure and mechanical characteristics of spark plasma sintered TiAl-matrix composites containing 3 wt% Si 3 N 4 and 3 wt% TiCN additives. Microstructural and phase studies reveal the development of TiAl and Ti 3 Al phases in monolithic TiAl, whereas the 3Si 3 N 4 /TiAl and 3TiCN/TiAl composites display additional in situ-formed phases, such as Ti 5 Si 3 , Ti 2 AlN, and Ti 3 AlC 2 . Specifically, a relatively homogeneous microstructure with well-dispersed reinforcing phases was achieved in the TiCN/TiAl composite compared to the 3Si 3 N 4 /TiAl composite. Among the sintered composites, the 3Si 3 N 4 /TiAl composite exhibited the maximum densification (~ 99.6%) and hardness of approximately 418 HV 0.5 . Conversely, the 3TiCN/TiAl composite exhibits superior compressive strength (~ 2378 MPa) and improved strain tolerance (~ 35.6%), while the 3Si 3 N 4 /TiAl composite only shows moderate improvement owing to the less effective load transfer and weaker interfacial bonding. Analysis of the fractured surface indicates that pure TiAl exhibits brittle intergranular fracture, while the 3Si 3 N 4 composite displays a mixed brittle-quasi-ductile mode. The 3TiCN/TiAl composite presents a more refined, energy-absorbing fracture mode. These results show the effectiveness of TiCN particles in optimising the structural integrity and mechanical performance of TiAl-matrix composites for advanced engineering applications.