| GH4169 Nickel-based alloy has been widely used in the fabrication of aircraft engines, large turbine disks, blades and other similar components. These components usually operate at high temperature and under creep-fatigue loading conditions. Creep-fatigue interaction will lead to an increase in the probability of failure for these components. Hence, the research on creep-fatigue resistance and failure mechanisms of GH4169 alloy at high temperature would provide life-design criterion of domestic key equipments. In this dissertation, the effects of strain waveform and grain size of material on the creep-fatigue resistance and initiation and propagation mechanism of crack of GH4169 alloy were investigated. The main research contents and conclusions are listed as below:(1) The microstructures and tensile properties of GH4169 alloy made by forging and hot rolling were identified before and after heat treatment. The difference of microstructure as well as tensile properties between GH4169 alloy made by forging and hot rolling were investigated.(2) The influences of strain range on high temperature low cycle fatigue behavior as well as initiation and propagation mechanism of crack of GH4169 were investigated. It was found that with decreasing the strain range, the number of crack sources decreased and the corresponding fatigue life increased. As strain ranges increased, the proportion of short cracks (<50μm) in the second cracks decreased gradually. However, the magnitude of strain range had no influence on the crack propagation mode.(3) The effects of microstructure, grain size and strain waveform on the creep-fatigue interaction and life of GH4169 alloy were investigated. As the grain size decreased, the hardness increased and creep-fatigue life decreased gradually. The introductions of both tension and compression would lead to the obvious reduction in creep-fatigue life. The tensile hold was more harmful to the creep-fatigue resistance at higher larger strain ranges. |
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