High-temperature fracture toughness of SiC–Mo5(Si,Al)3C composites

The fracture toughness (K1C) of melt-infiltrated SiC–Mo5(Si,Al)3C composites was measured from room temperature to 1400°C using the indentation strength method at 1 atm argon atmosphere. The fracture toughness was found to increase from 3.6 MPa·m1/2 at room temperature to 7.7 MPa·m1/2 at 1400°C. This increase was mainly attributed to the plastic deformation of the infiltrated Mo5(Si,Al)3C phases at high temperatures, which act as ductile toughening inclusions. The influence of annealing temperatures and atmospheres on K1C was studied. The effect of indentation load on K1C was also analyzed.