Effect of Mo coating on the interface and mechanical properties of SiC fiber reinforced Ti6Al4V composites

Ti6Al4V-matrix composites reinforced by continuous SiC fibers with Mo coating as interfacial modification layers were prepared by foil–fiber–foil method. Tensile strength of the as-prepared composites was tested, and thermal exposure of the composites in vacuum was carried out at 700 or 800 °C for different duration in order to investigate the thermal stability of Mo interlayer. Interfacial microstructure of the as-prepared and thermal-exposed composites was studied detailedly with the help of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transaction electron microscopy (TEM). The results show that, on the one hand, the original Mo coating becomes three layers: the residual Mo layer, a very thin layer of TiC (about 200 nm) and a mixed layer of Mo + β-Ti. In addition, there are two layers of the matrix that affected by the dissolution of Mo atoms between Mo + β-Ti layer and the normal matrix, which are identified to be β-Ti and a mixture of β-Ti with strip-like α-Ti, respectively. On the other hand, the tensile strength of the composites is significantly improved as the Mo coating can effectively hinder the fiber/matrix interfacial reaction, and the thermal exposure analysis indicates that Mo coating has excellent thermal stability when temperature is blow 700 °C.