Microstructure and mechanical properties of hot pressed ZrB 2-20SiC composite

摘要

AbstractIn this study effort has been made to evaluate micro structural features and corresponding mechanical properties such as bulk hardness, micro hardness, flexural strength and fracture toughness of the ZrB2-20vol% SiC composite before and after infra-red (IR) heating at 1400 and 1500°C for 600s. Volume fraction of the ZrB2-matrix phase and SiC reinforcing particulate phase of the composite remain same before and after IR heating. The surface of the composite after IR heating at 1400°C appears to be covered by a thin outer tetragonal SiO2layer, and a thin inner monoclinic ZrO2layer. Flower like morphology of these oxides is also observed in the oxide scale. Some penetration of oxide product inside the surface defects is also seen. Similar oxide scale is observed for 1500°C IR heated sample except the absence of flower like oxides morphology in this case. This marginal oxidation on the outer surface of the composite due to IR heating does not affect the mechanical properties of the composite. The mechanical properties such as, bulk hardness, micro hardness, flexural strength and fracture toughness of the composite do not get deteriorated after IR heating of the composite at 1400 and 1500°C for 600s rather it appears to improve slightly after IR heating possibly due to healing of the surface defects during IR heating.Highlights?There is no perceptible change in microstructure of ZrB2-20SiC composite occurred due to IR heating of the composite at 1400°C and 1500°C for 600 s. Volume fraction of matrix phase (ZrB2) and reinforcing particles (SiC) remain same after IR exposure.?A very thin SiO2layer on top of a mixed ZrO2-SiO2layer is observed in IR heated composite due to very limited time of exposure (600 s).?The mechanical properties such as flexural strength, hardness and fracture toughness of the composite do not get affected due to IR heating rather it appears to be slightly improved after IR heating. This may possibly due to healing of surface defects by penetration of oxide product in it.]]>