Effects of A1 Additions on Microstructure and Mechanical Properties of MoSi_2

摘要

The effects of Al additions on the microstructure and mechanical properties of MoSi2 have been studied. With the A1 additions from 2.5 wt pct to 5 wt pct, the siliceous grain boundary phase in hot pressed samples was eliminated because of the formation of Al2O3 particles. It was shown that Al and SiO2 reacted at 860℃. During the reaction, A1 atoms were mainly transferred to Al2O3 particles, and to some extent, diffused into MoSi2 grains. Both the toughness and strength of Al containing composites exceeded those of pure MoSi2 material. Bending strength and fracture toughness reach the highest value of 350 MPa, 4.05 MPa.m1/2, respectively, at ambient temperature when Al addition was of 3.5 wt pct.