压痕残余应力对氮化硅基复合材料阻力曲线行为的影响

THE INFLUENCE OF INDENTATION RESIDUAL STRESS ON THE RCURVE BEHAVIOR FOR SILICON NITRIDE BASED CERAMIC COMPOSITES

通过压痕小裂纹直接量测法获得ＴｉＣ，ＴｉＮ／Ｓｉ３Ｎ４复合材料的阻力曲线，采用更具合理性的指数经验公式拟合处理实验数据，初步探讨了Ｋ∞，Ｋ＊Ｒ，ΔＣ＊等参数的物理意义。对压痕残余应力消除前后的实验结果进行比较，发现压痕残余应力的消除，提高了材料的极限断裂韧性值Ｋ＊Ｒ，却大大减少了裂纹稳态生长的容限，使得材料的脆性行为更为突出。作为对比，基体材料的阻力曲线也一并进行了测量和研究。

Rcurves for TiC,TiN/Si 3N 4 ceramics are established by direct measurement of the change of Vickers indentation cracks in length under progressively applied bending stresses.A more reasonable empirical exponential relation is fitted for the data.Physical meanings of parameters,such as K ∞, K  R,and Δ C  are discussed.The experimental results before and after eliminating indentation residual stress are compared,and it is shown that the elimination of residual stress due to indentation improves the critical fracture toughness K  R,but decreases the cracking tolerance greatly,and makes the brittle behavior of material more apparent.For comparison,the Rcurve for the matrix material is also measured and discussed.