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本文研究了微观结构对718合金蠕变裂纹扩展行为的影响,对两种不同晶粒尺寸和三种不同碳化物分布的试样在650℃进行蠕变裂纹扩展试验。结果表明晶粒尺寸和碳化物结构显著影响蠕变裂纹扩展速率,蠕变裂纹扩展速率与晶粒尺寸成反比关系。碳化物成排且平行于裂纹试样的蠕变裂纹扩展抗力显著低于碳化物成排且垂直于裂纹的试样,更低于碳化物细小且均匀分布的试样。蠕变裂纹扩展速率与晶粒尺寸的反比关系归因于晶粒尺寸的增大使扩散路径增长,从而导致了微裂纹萌生和长大时间的增加。微观结构对718合金蠕变裂纹扩展行为的影响用蠕变裂纹扩展机理的三阶段模型给予了很好的解释。
In this paper, the effect of microstructure on the creep crack growth behavior of 718 alloy was studied. Two creep crack growth tests at 650 ℃ were carried out for two samples with different grain sizes and three different carbide distributions. The results show that the grain size and carbide structure significantly affect the creep crack growth rate, and the creep crack growth rate is inversely proportional to the grain size. The creep crack growth resistance of the carbides arranged in rows and parallel to the cracked specimen is significantly lower than that of the carbides arranged in rows and perpendicular to the crack, which is lower than that of the fine and uniformly distributed carbides. The inverse relationship between the creep crack growth rate and the grain size is attributed to the increase of the grain size and the increase of the diffusion path, which leads to the increase of the micro-crack initiation and growth time. Effect of microstructure on creep crack growth behavior of 718 alloy The three-phase model of creep crack propagation mechanism is well explained.