The fatigue behavior of 41Fe-25.5Ni-23.5Cr alloy welded joints subjected to different multistage post-weld heat treatment (PWHT) conditions was studied. The fatigue life of welded joints under PWHT1 (600 °C-1 h/1050 °C-1 h/950 °C-30 min) was significantly prolonged, which was attributed to the low cyclic hardening rate caused by the small cyclic yielding stress and effective stress. The microstructure analysis indicated that the twin boundaries in the fusion line maintained continuity with those in the base metal, causing the inhomogeneous fatigue deformation to be primarily distributed in the weld metal rather than the fusion line. The crystallographic orientation (0 0 1) of weld metal under PWHT1 remained unchanged during fatigue, the slip of bowed dislocation lines was the characteristics of fatigue deformation and the grain growth led to the decrease in weld metal deformation. The crystallographic orientation under PWHT2 (1050 °C-1 h) changed from (1 1 1) to (0 0 1), and the slip of tangled dislocation lines resulted in an accumulation of weld metal deformation. To study the impact of deformation behavior on fatigue properties, new dislocation slip models were developed based on the increase in dislocation density caused by the parabolic slip area and dislocation line length. The results of this study indicate that multistage PWHT is a remarkable approach to prolong the fatigue life of 41Fe-25.5Ni-23.5Cr alloy welded joints at high temperatures.

研究了 41Fe-25.5Ni-23.5Cr 合金焊接接头在不同多级焊后热处理 (PWHT) 条件下的疲劳行为。PWHT1 (600 °C-1 h/1050 °C-1 h/950 °C-30 min)下焊接接头的疲劳寿命显着延长，这归因于小的循环屈服应力导致的低循环硬化率和有效应力。显微组织分析表明，熔合线中的孪晶界与母材中的孪晶界保持连续性，导致不均匀疲劳变形主要分布在焊缝金属中，而不是熔合线中。晶体取向 (0  0 1）PWHT1下焊缝金属在疲劳过程中保持不变，弓形位错线的滑移是疲劳变形的特征，晶粒长大导致焊缝金属变形减小。PWHT2 (1050 °C-1 h) 下的晶体取向从 (1  1  1) 变为 (0  0  1)，并且缠结的位错线的滑移导致焊缝金属变形的累积。为了研究变形行为对疲劳性能的影响，基于抛物线滑移区和位错线长度引起的位错密度增加，开发了新的位错滑移模型。这项研究的结果表明，多阶段 PWHT 是延长 41Fe-25.5Ni-23.5Cr 合金焊接接头在高温下的疲劳寿命的显着方法。