Contribution of microstructure and slip system to cyclic softening of 9wt.%Cr steel

Effect of microstructural evolution on the cyclic softening of a 10% Cr martensitic steel under low cycle fatigue at 600 °C

“…So, changes in the strengthening from free dislocations and lath structure is more pronounced during the first half-life. This finding is in accordance with the results on the other 9%Cr martensitic steels [25,27]. The lower softening rate at the second half of cyclic testing is probably attributed to the fact that absorbed energy is mainly spent on the fatigue crack propagation at this stage.…”

“…The main microstructural changes contributing the cyclic softening consist in the decreasing the dislocation density by dislocation annihilation, coarsening of martensitic laths and transformation of lath structure into dislocation cell and subgrain structure [4][5][6][7][8][9][10][16][17][18][19][20][21][22][23][24]. Despite the fact that microstructural evolution leading to cyclic softening is considered in a limited number of works [25,26] the models describing a decrease in the dislocation density and the subgrain coarsening at elevated [23] and room [27] temperatures were developed. In contrast to creep, under LCF conditions the dispersion of secondary-phase particles changes insignificantly.…”

Evaluation of the effect of various prior creep-fatigue interaction damages on subsequent tensile and creep properties of 9%Cr steel

“…Moreover, the peak tensile stress of C-F test displays three softening stages: initial rapid softening stage, subsequent linear stable stage and final accelerated stage. The microstructure evolutions have been identified as the main reason for the observed cyclic softening behavior [38,39], which is illustrated in the following paragraph.…”

Influence of dynamic strain aging pre-treatment on the low-cycle fatigue behavior of modified 9Cr–1Mo steel

“…It has been reported that the variation of slip systems between {1 1 0}h1 1 1i and {1 1 2}h1 1 1i, depending on the Schmid factor, was responsible for the structure change from lath to dislocation cell structure [4]. DSA pre-treatment resulted in a high stress in Fig.…”

“…It is also a candidate material for use in the cladding of nuclear fuel, heat exchangers, reactor pressure vessels, and primary pipes for the next generation nuclear reactors [3,4]. The components of high-temperature systems are often subjected to repeated thermal stresses, which is due to temperature gradients, occurring on heating and cooling during start-ups and shut-downs or during temperature transients [5].…”