Microstructures and mechanical properties of hot-pressed MoSi2–matrix composites reinforced with SiC and ZrO2 particles

MoSi2–matrix composites reinforced with ZrO2 and SiC particles were fabricated by means of combustion synthesis (CS) combined with high-energy mechanical milling (MM) and hot-pressing and sintering. The microstructures and mechanical properties of the composites were investigated by X-ray diffractometry (XRD), scanning and transmission electron microscopy (SEM and TEM), and with a universal materials testing machine. The results show that SiC particles are mainly distributed inside the grains of the MoSi2 matrix, while ZrO2 particles are distributed at the inter-granular region and produce coalesence and coarsening of the matrix grains during hot pressing. The room-temperature indentation fracture toughness of the composites reinforced with ZrO2 particles non-stabilized by Y2O3 (the reinforcing agent is coded as 0Y-PSZ) was higher than that of the composites reinforced with ZrO2 particles stabilized by 2.5 mol% Y2O3 (the reinforcing agent is coded as 2.5Y-PSZ). However, the latter show higher bend strengths. Moreover, the composites hot-pressed at 1400°C has a lower bend strength than hot-pressed monolithic MoSi2. It is obvious that there is a synergistic effect of SiC and ZrO2 on the mechanical properties of ZrO2/(MoSi2+SiC) composites.