Si_3N_4-TiN/BN层状陶瓷材料阻力曲线及其增韧机制的研究

RESISTANCE-CURVE BEHAVIOR FOR Si_3N_4-TiN/BN LAMINATED COMPOSITES AND THEIR TOUGHNESS MECHANISM CONSIDERATION

通过压痕小裂纹直接量测法获得Si3N4-TiN/BN层状复合材料的阻力曲线 ,并采用指数经验公式拟合处理了实验数据 ,解释了各拟合参数的物理意义 .对层状复合材料阻力曲线所具有的独特的台阶状进行了分析 ,并对层状复合材料具有高韧性的机理作了深入的研究 .结果表明弱间层的层状结构具有明显的增韧效果 .这是由于弱间层的存在将出现裂纹偏转现象 ,吸收大量的断裂功 ,从而大幅度提高了裂纹的扩展容限 ,使断裂韧性有较大增长 .

R-curves for Si3N4-TiN/BN laminated composites are established by the direct measurement of the propagation of Vickers indentation cracks in length under progressively applied bending stresses. An empirical exponential relation is fitted for the data. The unique step shape of the R-curve of laminated composites is discussed. Moreover, the mechanism of high fracture toughness and prolonged crack tolerance shown in the R-curve deduction of laminated composites is further explained. The crack will deflect because the weak layer exits, which will absorb more fracture work and improve the crack tolerance greatly, therefore the fracture toughness increases remarkably.