Regulation of silicide phase in Nb-Si in-situ composites: Strategies and progress

Nb-Si in-situ composites have become candidate materials for hot-end components of aircraft engines due to their excellent high-temperature performance, whereas the inherent brittleness of high content silicides severely restricts their engineering applications. In this work, the strategies and research progress of phase control of silicides are systematically reviewed. The control mechanisms of alloying, preparation process, heat treatment and hot deformation on the type, morphology, size, distribution and phase transformation of silicides are mainly introduced, and the influences of corresponding microstructure evolution on the mechanical properties of alloys are also systematically clarified. For example, the combined alloying of Ti-Zr-Hf can increase the room-temperature fracture toughness of the alloy by 87.7%, and ultrasonic-assisted treatment yields a 69.16% improvement in fracture toughness compared with the traditional casting process. The problems of insufficient quantitative control and limited process adaptability in current silicide design are pointed out. The future development directions such as multi-process coupling, non-equilibrium preparation and multi-scale mechanical modeling are prospected, which provides theoretical support for the silicide design and engineering application of high-performance Nb-Si in-situ composites.