PAS烧结SiC-石墨复相陶瓷的阻力曲线行为和抗热震性能

R-curve behavior and thermal shock resistance of SiC-graphite composites prepared by PAS sintering process

采用PAS烧结工艺,在1 680℃成功制备出Si C-石墨复相陶瓷,并研究了石墨含量对复相陶瓷物理力学性能、韧性、R曲线(阻力曲线)行为和抗热震性能的影响。结果表明,随石墨含量的增加,复相陶瓷的致密度、抗弯强度、弹性模量和维氏硬度均有所降低;以韧化比(TI)作为复相陶瓷的韧性指标,表明石墨含量越多,复相陶瓷的韧性越好,存在陡峭的上升R曲线行为,该指标更能反映复相陶瓷的韧性特征;显微形貌分析发现,复相陶瓷中存在的层状石墨增加了能量耗损,裂纹在扩展过程中发生偏转、分叉和桥联等现象,使得Si C复相陶瓷的韧性和抗热震性能得以改善。

SiC-graphite ceramic composites were successfully fabricated by plasma activated sintering （PAS） method at 1 680 ℃ .The effects of graphite content on the physical mechanical properties, toughness, R-curve and thermal shock resistance of SiC-graphite composite were investigated. The experimental results show that the relative density, flexure strength, elastic modulus and hardness decrease with increasing graphite content.With TI as toughness index, the toughness of SiC-graphite composite is improved by increasing graphite content,which shows a sharp raising R-curve behavior.TI can really exhibit the toughness characteristic of SiC-graphite composites.Through the observation of the microstructures,the graphite plates existing in composites can consume more fracture surface energy during thermal shock.The cracks deflection, branching and bridging occur during cracks propagation, which improve the toughness and thermal shock resistance of SiC-graphite composites.