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本文在低碳马氏体型超高强度钢强韧性规律研究的基础上,系统地研究了疲劳断裂规律。试验结果表明,典型钢种25Si2Mn2CrNiMoV通过950℃加热油淬350℃回火,其疲劳强度(σ_(-1),σ_(-1N)等)和裂纹扩展抗力(dα/dN,ΔK_(th)等)可以实现最优化。通过对疲劳裂纹的原位透射电子显微分析,发现了疲劳裂纹尖端塑性区内板条马氏体晶体交界处的残余奥氏体薄膜发生应变诱发马氏体相变,观察到疲劳裂纹扩展过程中组织结构的变化情况,从而讨论了显微组织结构与疲劳断裂行为的对应关系。
Based on the study of the toughness and toughness of low-carbon martensitic ultra-high strength steel, the law of fatigue fracture has been systematically studied. The results show that the fatigue strength (σ _ (- 1), σ _ (- 1N), etc.) and crack propagation resistance (dα / dN, ΔK th etc.) of typical steel 25Si2Mn2CrNiMoV are tempered at 950 ℃ for 350 ℃. ) Can be optimized. Through the in-situ transmission electron microscopic analysis of the fatigue crack, strain-induced martensitic transformation was found in the residual austenite film at the martensite crystal boundary of the plastic zone of the fatigue crack tip, and the fatigue crack growth process was observed In the organizational structure changes, thus discussing the microstructure and fatigue fracture behavior of the corresponding relationship.