Masing Behavior and Microstructural Change of Quenched and Tempered High-Strength Steel Under Low Cycle Fatigue

Feng-Mei Bai^1,2，Hong-Wei Zhou³，Xiang-Hua Liu¹，Meng Song³，Ya-Xin Sun³，Hai-Long Yi¹，Zhen-Yi Huang²

1. State Key Laboratory of Rolling and Automation , Northeastern University2. School of Metallurgical Engineering , Anhui University of Technology3. School of Materials Science and Engineering, Anhui Key Lab of Materials Science and Processing , Anhui University of Technology

摘 要：Low cycle fatigue behavior of a quenched and tempered high-strength steel（Q960 E） was studied in the strain amplitude ranging from ± 0.5% to ± 1.2% at room temperature. As a result of fatigue loading, the dislocation structural evolution and fracture mechanism were examined and studied by transmission electron microscopy and scanning electron microscopy（SEM）. The results showed that this Q960 E steel showed cyclic softening at different strain amplitudes, and the softening tendency was more apparent at strain amplitude of ±（0.6–1.2）% than that at ± 0.5%. The reduction in dislocation density with increasing strain amplitude is responsible for the softening tendency of cyclic stress with the strain amplitude. The material illustrates near-Masing behavior at strain amplitude ranging from ± 0.6% to ± 1.2%. The near-Masing behavior of Q960 E high-strength steel can be the result of stability of martensite lath at different strain amplitudes. Partial transformation from martensite laths to dislocation cells is responsible for the derivation from ideal Masing behavior. In the SEM examination of fracture surfaces, transgranular cracks initiate on the sample surface. Striations can be found during the crack propagation stage.

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