Phase formation on the sintering of MoSi2 powder by Ni addition

The microstructural development of MoSi2 powder during the sintering process was observed, and the phases were analyzed in order to elucidate the mechanism of enhanced sintering at low temperatures. The sintered density was 5.76 +/- 0.04 g/cu cm after sintering for 1 h at 1550 C, which is about 200-300 C lower than the temperature at which the same sintered density of pure MoSi2 of 10 microns can be obtained. The Ni2Si phases segregated around particle necks, and these phases formed as thin films along the grain boundary during the sintering process. It is suggested that the (Mo,Ni)5Si3 phase is a by-product of the reaction between Mo5Si3 and Ni2Si phases. (AIAA)