Effects of Al additions on the microstructure and mechanical properties of MoSi2

The effects of At additions on the microstructure and mechanical properties Of MoSi2 were studied. With the At additions from 2.5 wt% to 5 wt%, the siliceous grain boundary phase in hot pressed samples was eliminated because of the formation of Al2O3 particles. It is shown that Al and SiO2 will react at 860 degreesC. During the reaction, Al atoms are mainly transferred to Al2O3 particles, and to some extent, diffuse into MoSi2 grains. Both the toughness and strength of Al containing composite exceed those of pure MoSi2 material. Bending strength and fracture toughness reach the highest value of 350 MPa, 4.05 MPam(1/2), respectively, at ambient temperature when Al addition is of 3.5 wt%.