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

• Microstructure of Nb/Nb5Si3 composite alloyed with W and Mo is change obviously.
• W and Mo elements can solid solution in Nb and Nb5Si3 phase respectively.
• Alloyed with W and Mo, the solid solubility of Nb5Si3 phases is undetected.

Microstructures of Nb/Nb5Si3 composites and it 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 Nb/Nb5Si3 composites include primary Nb and eutectic mixtures of Nb and Nb5Si3, and the coarse and fine eutectic mixtures are detected. The microstructure of Nb/Nb5Si3 composites alloyed with W or Mo is unaltered, and W and Mo elements solid solution in Nb and Nb5Si3 phase are detected, but that alloyed with W and Mo together, The microstructures are change 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.