镍基高温合金GH4145/SQ的高温低周疲劳行为

Hi-temp-low-cycle Fatigue Bahavior of Ni-based High temperature Alloy GH4145/SQ

主要研究了镍基合金 GH41 45 /SQ在 5 3 8℃高温下的低周疲劳行为与微细观机制。应变控制对称拉压疲劳试验结果表明 ,在循环形变过程中合金主要表现为初始疲劳硬化、随后疲劳软化及最终失稳断裂三个阶段 ,疲劳硬化 /软化速率与作用应变幅密切相关。合金的循环应力—应变曲线和应变—寿命曲线呈现出一定的双线性特征 ;对不同疲劳阶段的金相组织结构检查则揭示出 ,循环塑性应变作用将显著改变合金中沉淀颗粒的几何形状、尺寸和分布状态 ,并将改变位错与颗粒之间的交互作用行为 ,这一机制对合金的循环硬化和软化起促进作用 ;对不同应变幅下疲劳断口的扫描电镜 (SEM)观察则进一步表明了疲劳断口微观形貌特征与作用应变幅相依 ,随着控制应变幅减小 。

The low cycle fatigue behavior of Ni based alloy GH4145/SQ under 538 ℃ and its micro mechanizm have been studied. The fatigue test of stress control symetric tension compression showed that in the duration of cycling mislocation, the main process is begining with fatigue hardening, then follows with fatigue softening and finally the metal loses stability and fractures. The rate of fatigue hardening/softening has close relationship with the acted stress amplitade. The examinations for metallurgical structure of different fatigue stage reveals that the action of cycling plastic stress will significantly change the geometric form, size and distribution of the precipitating particles in the alloy and also change the interactional behavior between the particles and mislocation and this mechanizm has a promoting effect on cycling softening/hardening of the alloy. With the help of SEM, a further positive explanation for the above statement can be made.