Oxidation of Nb/Nb5Si3 In Situ Composites Fabricated via Spark Plasma Sintering with Al Addition

Dense Nb/Nb5Si3 composites were fabricated via spark plasma sintering technology using Nb, Si, and Al elemental powders as raw materials. The microstructures of the synthesised composites were analysed through scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. The results show that the composites consisted of residual Nb particle phase and Nb5Si3 phase. The microstructure of the Nb/ Nb5Si3 in situ composites was evidently affected by Al addition, which prompted the formation of the Al3Nb10Si3 phase. The oxidation resistance of the Nb/Nb5Si3 in situ composites significantly improved with the increase in Al addition. Pesting oxidation behaviour was exhibited at 800°C by the Nb-20Si composites when exposed to air for 4h. This pest oxidation behaviour is not exhibited by the Nb-20Si-10Al and Nb-20Si-15Al composites after exposure to air for ~10h. The composite exhibits the best oxidation resistance at 15at% Al.