AIN和B对热压烧结C_f/SiC复合材料性能的影响

Effects of AIN and B on the Carbon Fiber Reinforced Silicon Carbide Matrix Composites

研究了烧结助剂ＡＩＮ 和Ｂ对Ｃｆ／ＳｉＣ复合材料力学性能的影响。结果表明：Ｂ含量较低时（小于０．５ｗ ｔ％ ），Ｂ的增加能有效地提高复合材料的抗弯强度与断裂韧性，继续增加Ｂ的用量至１ｗ ｔ％ ，虽能大幅度提高复合材料的强度，但使复合材料的断裂韧性大大降低。ＡＩＮ 与ＳｉＣ高温反应形成固溶体，能起到强化和细化基体ＳｉＣ晶粒以及改善ＳｉＣ晶界结构的作用，但对复合材料内纤维与基体间界面的结合影响较小，因此与Ｂ的作用相比，ＡＩＮ 对复合材料密度和力学性能的影响较小。烧结助剂为５ｗ ｔ％ ＡＩＮ－０．５ｗ ｔ％ Ｂ，经１８５０℃和２５ＭＰａ 热压烧结后的Ｃｆ／ＳｉＣ复合材料具有较佳的综合力学性能，其抗弯强度与断裂韧性值分别为５２６．６ＭＰａ 和１７．１４ＭＰａ·ｍ １／２。

The effects of the composition and amount of additives (AIN and B) on the mechanical properties of C/SiC composites were investigated. The mechanical properties were obviously improved by introducing trace amount of B. Increasing the amount of B up to 1wt%, the flexural strength can be improved significantly, but the composite shows lower fracture toughness. Though leading to the strengthening and fining of the SiC grains as the result of the formation of AIN SiC solid solution, AIN has minute effect on the interface between the fiber and matrix, so the change of the mechanical properties are mainly attributed to B. The flexural strength and fracture toughness of the C/SiC composite containing 5wt% AIN adn 0 5wt%B, sintered at 1850℃ under a pressure of 25MPa, reach 526 6MPa and 17 14 MPa·m 1/2 respectively.