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

SiCf/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, SiCf/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 SiCf/C/Mo/Ti2AlNb composites are much better than those of the SiCf/C/Ti2AlNb composites, as the C/Mo duplex coating can reduce the formation of brittle alpha(2)-phase and relieve the interfacial thermal residual stresses in SiCf/Ti2AlNb composites compared with C single coating. After the 1080 degrees C/1 h/850 degrees C/20 h heat treatment, the matrix of the SiCf/C/Mo/Ti2AlNb composite transformed into mainly B2 + O homogenous mixture and a small amount of alpha(2) 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.