Enhancing mechanical performance of Ti–Mo–Si titanium matrix composites via Al-doped MoSi2 addition

Abstract

Ti–Mo–Si titanium matrix composites (TMCs) with high Si content are potential for high-temperature applications but show limited mechanical properties at room temperature due to the severe Ti–Si interfacial reaction. In this work, we propose a novel reinforcement alloying strategy to improve the interface bonding between matrix and reinforcement and enhance the room temperature mechanical properties of the Ti–Mo–Si TMCs. Specifically, the MoSi2 compound was mechanical alloyed with minor Al, then the effects of Al-doped MoSi2 addition on the microstructure, mechanical properties, fracture behavior and strengthening mechanisms of the Ti–Mo–Si composites were studied systematically. With the addition of Al-doped MoSi2, the matrix microstructure of the Ti–Mo–Si composites was refined and the mechanical properties were improved significantly. Notably, the TMC reinforced by 4 wt% Al-doped MoSi2 shows higher tensile strength and bending strength (766 MPa and 2616 MPa) than those of TMC (733 MPa and 2236 MPa) without Al-doping, respectively. The increase in strength is mainly attributed to the decrease in the volume fraction of Ti5Si3 and the tight interface bonding between the matrix and the reinforcement, leading to a high load transfer efficiency and a uniform strain distribution. In addition, dislocation strengthening and grain boundary strengthening play the key role in governing overall strength the Ti–Mo–Si composites.