On the microstructural evolution in a 10% Cr martensitic steel during interrupted low cycle fatigue testing at 650 C

The correlation between cyclic softening and microstructural evolution using the interrupted low cycle fatigue (LCF) tests with a low strain amplitude of & PLUSMN;0.2% at 650 & DEG;C in a 10% Cr steel was studied. Cyclic softening was analyzed in terms of the friction and back stresses caused by short-range and long-range obstacles, respectively. Softening was mainly attributed to a decrease in the friction stress due to the dislocation annihilation. Whereas the back stress remained more stable due to additional precipitation on the lath boundaries, despite the intense lath widening caused by the disappearance of lath boundaries.