Microstructures and mechanical properties of Nb/Nb5Si3 composites alloyed with W, Mo and W–Mo fabricated by spark plasma sintering

Microstructures and mechanical properties of Nb/Nb5Si3 composites alloyed with W, Mo and W–Mo fabricated by spark plasma sintering were investigated. The microstructures were examined using scanning electron microscope (SEM). X-ray diffraction (XRD) was performed on the bulk specimens for identification of phases. The chemical species were analyzed using electron-probe micro-analysis (EPMA). Results indicated that the microstructures of Nb/Nb5Si3 composites alloyed with W or Mo is unaltered, including primary Nb and eutectic mixtures of Nb and Nb5Si3, and the coarse and fine eutectic mixtures. The W and Mo elements solid solution in Nb and Nb5Si3 phase are detected. But that alloyed with W and Mo together. The microstructures are changed obviously, including Nb phase, the solid solubility phases of W and Mo atoms in Nb, and the solid solubility phases of Nb atoms in W are also found, but the solid solubility phenomenon of Nb5Si3 phases is not detected. The microhardness of Nb and Nb5Si3 phases increases obviously because of solid solution strengthening. The excellent high temperature tensile strength of Nb−20Si−10W−10Mo sample was obtained. It is attributable to granular Nb surrounding by Nb5Si3 phase in eutectic, which different with interlamellar eutectic.