In situ pressureless sintering of SiC/MoSi2 composites

SiC-reinforced MoSi2 composites have been successfully prepared by in situ pressureless sintering from elemental powders of Mo, Si and C. Meanwhile, the evolutions of the samples’ microstructure and phase at different temperatures were investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with an energy dispersive X-ray spectrometer (EDS). It can be seen that at the temperature of 1100 °C, the main phases were Mo and Si, accompanying with a small amount of rich molybdenum products Mo5Si3 and Mo3Si. Then the main phases changed to MoSi2 and SiC when the sintering temperature reached 1300 °C. Finally we obtained MoSi2/SiC composites with well-dispersed SiC particles after sintering at the temperature of 1550 °C for 120 min. The evolution of porosity in these composites fits the porosity reduction model well developed by Pines and Bruck, which revealed the particle agglomeration in the composites. The flexural strength and fracture toughness of 10% SiC/MoSi2 composites were up to 274.5 MPa and 5.5 MPa m1/2, increased by approximately 40.8% and 30.6% compared with those of monolithic MoSi2, respectively.