Effect of solution and aging treatment on the microstructure and tensile properties of SiC_f/C/Mo/Ti₂AlNb composites

SiC_f/C/Mo/Ti₂AlNb composites were prepared by foil-fiber-foil (FFF) method and are used as model system to study the effect of solution-ageing treatments on the interface and mechanical properties of SiC fiber-reinforced TiAl-matrix composites. By contrast, SiC_f/C/Ti₂AlNb composites were prepared and heat treated under the same process parameters. The interfacial microstructures of the as-prepared and heat treated composites were investigated by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Tensile strength tests of the composites were carried out at room temperature. So the effect of C/Mo duplex coated SiC fibers on the microstructure and tensile behavior of the composites was studied. The results reveal that the interfacial thermal stability and integrity of the SiC_f/C/Mo/Ti₂AlNb composites are much better than those of the SiC_f/C/Ti₂AlNb composites, as the C/Mo duplex coating can reduce the formation of brittle α₂-phase and relieve the interfacial thermal residual stresses in SiC_f/Ti₂AlNb composites compared with C single coating. After the 1080 °C/1 h/850 °C/20 h heat treatment, the matrix of the SiC_f/C/Mo/Ti₂AlNb composite transformed into mainly B2+O homogenous mixture and a small amount of α₂ phase, and the tensile strength of the composite was tested, which shows that the tensile properties of the composite was maintained after the solution-ageing treatment.