纳米SiC增韧Al_2O_3陶瓷复合材料的制备、表征及力学性能研究

Preparation, Characterization and Mechanical Properties of Nano-Si C Toughened Al_2O_3 Matrix Composites

以SiC和Si微米粉为添加剂,采用无压烧结工艺制备了纳米SiC增韧的Al2O3陶瓷复合材料,探讨了SiC含量、烧结气氛和烧结温度对复合材料的烧成收缩率、微观形貌、抗弯强度、维氏硬度及断裂韧性的影响。结果显示:SiC的添加使复合材料的烧成收缩率下降,惰性气氛下复合材料的收缩率要大于氧化气氛和还原气氛时的收缩率。在氧化性气氛下烧结时,当SiC添加量为4%时,复合陶瓷的体积密度为3.80 g·cm-3,抗弯强度、断裂韧性及维氏硬度均达到最大值,分别为480 MPa、5.12 MPa·m1/2、16.2 GPa。添加SiC后所得复合材料的基体颗粒为椭圆状,粒径为2μm左右,颗粒与颗粒之间结合紧密,颗粒形状的改变可能是因为烧结机理发生变化所致。纳米SiC颗粒位于晶界处,形成了由Al2O3-SiC-Al2O3搭桥联结的晶界,提高了晶界强度,导致裂纹只能在晶内传播。

Nano-Si C toughened Al2O3 matrix composites were prepared using pressureless sintering method, in which Si C and Si micron powders were used as additives. Influence of Si C content, sintering atmosphere and sintering temperature on the shrinkage rate, microstructure, flexural strength, hardness and fracture toughness of the Al2O3 matrix composites was studied. Results showed that addition of Si C resulted in a reduction of shrinkage rate for composites, and the shrinkage rate of composites obtained in an inert atmosphere was higher than that of the composites obtained in both oxidized and reduced atmospheres. When the Si C content was equal to 4%, the volume density of the composites was 3.80 g·cm^-3, their flexural strength, Vickers hardness and fracture toughness reached the maximum, i.e., 480 MPa, 5.12 MPa·m1/2, 16.2 GPa, respectively. Their particles were oval in shape with a size of about 2 μm and combined compactly with each other. A change of particle shape from plate to oval may have derived from the alternation of sintering mechanism. Nano Si C particles, which existed in Al2O3 crystals and formed Al2O3-Si C-Al2O3 bridges, resulted in a transcrystalline rupture of composites.