Microstructure and mechanical properties of multi-phase TiAl alloy matrix composites consolidated via field-assisted sintering technique

Abstract

In this study, fully densified Si3N4/TiAl composites were fabricated using the field-assisted sintering technique (FAST). Microstructural analysis showed the evolution of a continuous network structure consisting of minor fractions of in-situ formed Ti2AlN, unreacted Si3N4 ceramic particles and dominant Ti5Si3 intermetallic phases within the TiAl matrix at Si3N4 content above 1.5 wt%. The hardness of the developed composites increases with increasing Si3N4 content, with 7Si3N4/TiAl composite exhibiting the highest hardness of approximately 487 HV1.0, which was about 57% higher than that of the sintered pure TiAl alloy. Among the sintered samples, 1.5Si3N4/TiAl composite displayed the highest flexural strength of 832.65 ± 12.88 MPa (34.3% higher than pure TiAl matrix) with a deflection of 0.14 mm. In contrast, the lowest flexural strength and deflection of 535.44 ± 21.14 MPa and 0.09 mm were obtained in composite reinforced with 7 wt% Si3N4 ceramic content. The fractured surface of the sintered samples displayed predominantly cleavage fracture mode.