采用扫描电镜原位观测的方法,跟踪观察了低周疲劳载荷作用下超高强度钢中AlN夹杂导致裂纹萌生与扩展的微观行为,得到了材料疲劳裂纹表面长度与内部长度之间的关系,可以根据实际检测到的材料或者结构疲劳裂纹表面长度计算其内部长度,并估算其剩余寿命.

Ultra-high strength steel makes advancement incessantly with development of aeronautical industry.However,its sensitivity to the flaw increases with increasing in strength level.Non-metallic inclusion as one of the inevitable flaws must influence the performance,especially fatigue performance,of ultra-high strength steel.In-situ fatigue tests with special designed SEM have been conducted to trace the whole process of crack initiation and propagation induced by AlN inclusion in ultra-high strength steel under low-cycle fatigue load.The strong linear between the surface length and the inside length of fatigue crack was gained.The inside length can be calculated based on the surface length of fatigue crack detected in material or structure and the residual life can be estimated.