高碳当量灰铸铁低周疲劳行为研究

Study on Low Cycle Fatigue Behavior of High Carbon Equivalent Gray Cast Iron

研究了高碳当量灰铸铁的常温低周疲劳行为。恒应变幅疲劳试验表明:高碳当量灰铸铁的循环断裂次数较小,且随应变幅增加而减小。疲劳断口分析表明:疲劳裂纹萌生于试样表面、铸造缺陷和片状石墨尖端处,且沿石墨片扩展,其疲劳断裂方式为沿晶脆断;高碳当量灰铸铁组织中片状石墨较多,对基体造成切割作用,促进裂纹扩展,加速疲劳断裂进程。

The low cycle fatigue behavior of high carbon equivalent gray cast iron at room temperature was studied by the use of electro-hydraulic servo static universal testing machine, metallographic microscope and scanning electron microscopy. The constant strain fatigue test shows that the number of cyclic fractures of high carbon equivalent gray cast iron is small, and it decreases with increasing strain amplitude. Fatigue fracture analysis shows that the fatigue cracks are initiated on the surface, casting defects and flaky graphite tips, and the cracks propagated along the graphite. The fatigue fracture mode is intergranular brittle fracture. A large number of flaky graphites exist in high carbon equivalent gray cast iron, which cut the matrix, promote the expansion of the crack and accelerate the fatigue fracture process.