Effects of Al additions on Microstructure of Hot Pressed MoSi_2

The effect of Al additions on the microstructure of hot pressed MoSi2 was studied, and theconcept of t ran s it ion- gas- phase-sintering was proposed. The results indicate t hat t he SiO2 phaseon grain boundary is eliminated by the reaction of Al and SiO2 while the Al2O3 particles areproduced, and the MoSi2 lattice is changed because of the diffusion of Al atoms. Furthermore,the sintering is advanced because of the deformation of MoSi2 lattice and the disappearance ofresidual gas which is replaced by Al vapor in isolated pores, so porosity is reduced. The porosityis the lowest when Al additive is 3.5 wt%.