Microstructures of Nb/Nb_5Si_3 composites and it alloyed with W, Mo and W-Mo fabricated by spark plasma sintering

摘要

Microstructures of Nb/Nb_5Si_3 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/Nb_5Si_3 composites include primary Nb and eutectic mixtures of Nb and Nb_5Si_3, and the coarse and fine eutectic mixtures are detected. The microstructure of Nb/Nb_5Si_3 composites alloyed with W or Mo is unaltered, and W and Mo elements solid solution in Nb and Nb_5Si_3 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 Nb_5Si_3 phases is not detected. The microhardness of Nb and Nb_5Si_3 phases increases obviously because of solid solution strengthening.