Cyclic responses of a novel heat resistant martensitic steel, 9Cr3Co3W1CuVNbB steel, under different loading modes were studied to reveal its complex strengthening mechanisms at high temperature. Based on the experimental observations, dislocation strengthening, precipitation strengthening by M₂₃C₆ phase, MX phase, and Cu-rich phase, and subgrain boundary strengthening were the main mechanisms for its excellent fatigue and creep-fatigue properties. In particular, the dynamic process of interaction between phase and dislocation were studied with the help of molecular dynamics method, and the different contributions of hard and soft phases in the studied steel were determined in fatigue and creep-fatigue loading. Based on these phenomena, a physically-based constitutive model was proposed for both fatigue and creep-fatigue (dwell fatigue at elevated temperature) tests considering various micromechanical mechanisms. Three ways for dislocation annihilation were proposed to simulate the dislocation evolution under different loadings. In addition, the effect of Cu-rich phase was modeled by critical breaking angle and dislocation line tension. The capability of the proposed model under different loading modes was verified by comparing cyclic responses, hysteresis loops, stress relaxation, and dislocation density evolution. The proposed model provides an alternative perspective on understanding fatigue and creep-fatigue behaviors of heat resistant martensitic steels owning the similar strengthening mechanisms.

研究了新型耐热马氏体钢 9Cr3Co3W1CuVNbB 钢在不同加载模式下的循环响应，以揭示其在高温下复杂的强化机制。根据实验观察，M ₂₃ C _{6位错强化、析出强化}相、MX 相和富 Cu 相以及亚晶界强化是其优异的疲劳和蠕变疲劳性能的主要机制。特别是，借助分子动力学方法研究了相和位错之间相互作用的动态过程，并确定了所研究钢中硬相和软相在疲劳和蠕变疲劳载荷中的不同贡献。基于这些现象，提出了一种基于物理的本构模型，用于考虑各种微观机械机制的疲劳和蠕变疲劳（高温下的驻留疲劳）测试。提出了三种位错湮灭方法来模拟不同载荷下的位错演化。此外，富铜相的影响通过临界断裂角和位错线张力来模拟。通过比较循环响应、滞后回线、应力松弛和位错密度演化，验证了所提出模型在不同加载模式下的能力。所提出的模型为理解具有类似强化机制的耐热马氏体钢的疲劳和蠕变疲劳行为提供了另一种视角。