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研究了2种高温条件下镍基单晶合金的低周疲劳行为。试验温度和总应变幅是影响合金低周疲劳寿命的2个主要因素,在相同温度下,低周疲劳寿命随应变幅的减小而增大;在同一应变幅下,870℃的疲劳寿命均小于760℃的疲劳寿命。二次细小y相有效阻碍了位错的滑移,提高了合金在760℃低周疲劳变形抗力,位错滑移带成为疲劳裂纹萌生及扩展的主要途径;870℃循环应力曲线前期出现短暂硬化和后期软化的现象,y’相逐渐粗化和高密度的位错缠结是循环软化的主要原因。局部应力集中与合金内微孔的交互作用是疲劳裂纹萌生的源头。
The low cycle fatigue behavior of nickel base single crystal alloys under two kinds of high temperature conditions was studied. The test temperature and the total strain amplitude are the two main factors affecting the low cycle fatigue life of the alloy. At the same temperature, the low cycle fatigue life increases with the decrease of the strain amplitude. At the same strain amplitude, the fatigue life at 870 ℃ Fatigue life less than 760 ℃. The secondary fine y-phase effectively impedes the slip of dislocations, improves the low-cycle fatigue resistance of the alloy at 760 ℃, and the dislocation slip band becomes the main path of fatigue crack initiation and propagation. The early period of 870 ℃ cyclic stress curve appears short-term hardening And late softening phenomenon, y ’phase coarsening and high-density dislocation entanglement is the main reason for the cycle of softening. The interaction between local stress concentration and micropores in alloy is the source of fatigue crack initiation.