硬质相晶粒尺寸对Mo_2FeB_2基金属陶瓷断裂韧性的影响

Effect of Grain Size on Fracture Toughness of Mo_2FeB_2-based Cermets

以Mo、Fe、FeB等为原材料,采用最高烧结温度(保温时间)分别为1 170℃(0 min)、1 250℃(0 min)以及1 250℃(40 min)的真空烧结工艺制备了硬质相晶粒尺寸不同的Mo2FeB2基金属陶瓷,所得烧结体的硬质相晶粒尺寸分别为1.12、1.31和1.73μm。利用压痕法测定了Mo2FeB2基金属陶瓷的断裂韧性。结果表明:Mo2FeB2基金属陶瓷的断裂韧性随着硬质相晶粒尺寸的增加而增大,当晶粒尺寸从1.12μm增加到1.73μm时,Mo2FeB2基金属陶瓷的断裂韧性从11.4 MPa·m1/2增加到14.2 MPa·m1/2。随着硬质相晶粒尺寸增加,裂纹偏转增强,并出现裂纹桥联和晶粒拔出现象,导致裂纹扩展路径和能量消耗增大,从而提高了Mo2FeB2基金属陶瓷的断裂韧性。

Using Mo, Fe, FeB and some other additives as raw materials, a series of Mo2FeB2-based cermets with different grain sizes were produced by vacuum sintering processes with the highest sintering temperature （time） of 1 170 ℃ （0 min）, 1 250 ℃ （0 min） and 1 250 ℃ （40 min）. The gained grain sizes of the cermets were 1.12, 1.31and 1.73 μm, respectively. The fracture toughness was measured by the indentation method. The results show that the fracture toughness increases gradually with the increase of grain size, which is characterized by the increase of crack deflection, cracks bridging and particles extracting. When the grain size increases from 1.12 μm to 1.73 μm, the fracture toughness increases from 11.4 MPa.m^1/2 to 14.2 MPa.m^1/2. The fracture toughness of Mo2FeB2-based cermets is improved with the increase of crack propagation path and energy consumption.