微波烧结WC-ZrO2复合材料的微观组织及增韧机理

Microstructure and Toughening Mechanism of WC-ZrO_2 Composites by Microwave Sintering

采用微波烧结工艺制备超细晶WC-ZrO_2复合材料,研究了其显微组织和力学性能。结果表明:ZrO_2含量为10 wt%、烧结温度为1360°C时获得的WC-10ZrO_2复合材料综合性能良好,致密度达98.50%,其断裂韧性和硬度分别为8.13 MPa·m^(1/2)和21.81 GPa。随着烧结温度的升高,致密度增大,硬度也随之升高。温度达到1320°C时,硬度达到最高值22.58 GPa。继续升高温度,晶粒粗化导致硬度降低,但断裂韧性随温度升高不断增大。烧结温度为1360°C时,纯WC试样的硬度为23.92 GPa,当ZrO_2含量增加至14 wt%时,材料的硬度降低至21.3 GPa,但韧性却由4.04 MPa·m^(1/2)大幅度提高至9.60 MPa·m^(1/2)。WC-ZrO_2复合材料断裂主要表现为穿晶断裂,ZrO_2颗粒阻碍了裂纹的扩展,使裂纹发生偏转、绕行和桥接,增加裂纹扩展路径,从而达到增韧的效果。

In this paper,the ultrafine-grained WC-ZrO2 composites were fabricated by microwave sintering.The microstructure and mechanical properties of the composites were studied.The results showed the WC-10ZrO2 composite fabricated at 1360℃exhibited excellent comprehensive mechanical properties.It had a relative density of 98.50%,a fracture toughness of 8.13 MPa·m^1/2 and a hardness of 21.81GPa.With the increase of sintering temperature,relative density and hardness increased simultaneously;Hardness reached the highest value of 22.58 GPa at 1320°C.but when the sintering temperature was over 1320°C,hardness decreased because of grain coarsening.Fracture toughness increased with sintering temperature.Sintered at 1360°C,hardness of pure WC was 23.92 GP and fracture toughness was 4.04 MPa·m^1/2.When the content of ZrO2 increased to 14 wt%,hardness decreased to 21.3 GPa,but fracture toughness was significantly increased from 4.04 MPa·m^1/2 to 9.60 MPa·m^1/2.The fracture mechanisms of WC-ZrO2 composites include mainly transgranular rupture,ZrO2 particles hindered the extension of crack,made crack deflection,bypass and bridging,increased the crack propagation path,thus achieved toughening effect.