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

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. (C) 2013 Elsevier B. V. All rights reserved.