拉保持对316L奥氏体不锈钢焊接接头低周疲劳循环应力响应及损伤机制的影响

在873 K温度下对316L奥氏体不锈钢母材和焊缝分别进行连续和拉保持低周疲劳试验,使用光学显微镜(OM)和透射电镜(TEM)对试样位错微观结构和裂纹扩展形貌进行观察,分析拉保持对母材和焊缝低周疲劳循环应力响应及损伤机制的影响.结果表明,母材在连续和拉保持低周疲劳试验初期都发生循环硬化,焊缝在连续低周疲劳试验中发生连续循环软化,而在拉保持试验后期则出现明显循环稳定阶段;母材和焊缝试样拉保持低周疲劳寿命低于其连续低周疲劳寿命;母材和焊缝在连续低周疲劳试验中裂纹主要以穿晶方式扩展,而在拉保持试验中焊缝是以沿晶或混合方式扩展.

Effect of tensile dwell on low cycle fatigue cyclic stress response and damage mechanism of 316L austenitic stainless steel welding joint

Continuous and tensile dwell low cycle fatigue tests of 316 L austenitic stainless steel base metal and weldment were carried out at 873 K temperature. The dislocation microstructure and crack propagation evolution in the specimens were examined using optical microscope(OM) and transmission electron microscopy(TEM). The effect of tensile dwell on the low cycle fatigue cyclic stress response and damage mechanism of base and weld metal was experimentally investigated. Cyclic hardening was observed in the base metal during both continuous and tensile dwell low cycle fatigue tests. However, continuous cyclic softening was observed during continuous low cycle fatigue in the weldment whereas clear cyclic saturation stage occurred during tensile dwell test. The fatigue life during tensile dwell low cycle fatigue was much shorter than that during continuous low cycle fatigue. Transgranular propagation of crack was the main character during continuous low cycle fatigue for both base metal and weldment. However, the crack propagated intergranularly or in mixed mode during tensile dwell low cycle fatigue test.