【摘要】 研究热机疲劳载荷下不同疲劳周次和应变幅值对316L后续拉伸性能的影响，使用金相显微镜和扫描电子显微镜对断口以及断口附近表面形貌进行分析，并使用透射电镜观察不同疲劳周次下的位错结构，最后基于拉伸性能提出剩余疲劳寿命预测方法。结果表明，热机疲劳周次和应变幅值对拉伸性能的影响趋势明显不同，热机疲劳周次对拉伸性能的影响显著大于应变幅值的影响。热机疲劳周次和应变幅值的增加导致试样表面出现明显的宏观裂纹，材料韧性下降，在热机疲劳周次达到50%N_f之后，试样的断裂模式由单纯的韧性断裂转变为混合断裂，热机疲劳过程中的位错结构演化是导致材料强度增加的主要原因。基于均匀延伸率、延伸率、均匀拉伸塑性应变能以及拉伸塑性应变能对剩余疲劳寿命进行预测，其中基于均匀拉伸塑性应变能的预测结果最为准确。更多还原

【Abstract】 The effects of fatigue cycle and strain amplitude of thermo-mechanical fatigue loading on the subsequent tensile properties were investigated.Metallographic microscopy and scanning electron microscopy were used to analyze the fracture surface and the surface morphology near the fracture location.Transmission electron microscopy was also used to observe the dislocation structure under different fatigue cycles.Finally, a remaining fatigue life prediction method was proposed based on the tensile properties.Results show that the effects of thermo-mechanical fatigue cycle and strain amplitude on tensile properties show different trends, in which, the effect of thermo-mechanical fatigue cycles on tensile properties was found to be significantly greater than that of strain amplitude.As the fatigue cycles and strain amplitude increase, obvious macroscopic cracks appear on the specimen′s surface, inducing a reduction in material toughness.Fracture mode changes from a ductile fracture to a mixed fracture mode after the fatigue cycles reach 50%N_f.The evolution of the dislocation structure during thermo-mechanical fatigue was identified as the main reason for the enhancement of tensile strength.Subsequently, the remaining fatigue life was predicted based on the uniform elongation, elongation, uniform tensile plastic strain energy and tensile plastic strain energy, among which the fatigue life prediction based on the uniform tensile plastic strain energy was the most accurate.更多还原