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The study aims to analyze the tensile behavior and microstructural changes in MAR‐M247 nickel‐based superalloy across different temperatures. Tensile behavior is examined under a constant strain rate of 2.5 × 10−4 s−1 at varying temperatures. Results indicate a temperature‐dependent nature of the alloy's tensile properties. At 550 °C, a Portevin–Le Chatelier effect is observed, attributed to twinning nucleation and carbon atom diffusion. Dynamic recrystallization occurs at 950 °C, manifesting in a sinusoidal stress–strain curve. At room temperature, the primary fracture mechanism involves dislocation shearing in the γ matrix, with minor dislocation shearing in the γ′ phase. At 550 °C, carbides along grain boundaries and the γ′ phase impede dislocation motion. Concurrently, dislocations shear the γ′ phase, leading to the formation of superlattice intrinsic stacking faults and Kear–Wilsdorf locks, thereby enhancing tensile strength. However, at 950 °C, dislocation motion primarily involves climb, carbides decompose, the γ′ phase softens and enlarges, resulting in a notable decrease in tensile strength. [ABSTRACT FROM AUTHOR]

During steam turbine rotor operation, the startup and showdown processes can cause asymmetric loading stress, leading to fatigue damage. To research the cyclic deformation behavior and fatigue failure mechanisms of 9% Cr‐based steel under asymmetric loading conditions, the strain ratios including −1, 0, and 0.1 are introduced into the low cyclic fatigue tests at 430°C. The results show the cyclic softening behavior is observed under three strain ratios at 430°C. As the strain ratio increases, the crack initiation sources, plastic strain, and consumed energy present an increasing trend. Comparing the microstructure morphology at different strain ratios, the coarsening lath and carbides affect fatigue crack initiation. Besides, the grain rotation and dynamic recrystallization can be observed, resulting in the cyclic softening behavior during the fatigue test. Finally, a new fatigue life prediction model is proposed at 430°C. Highlights: The low cycle fatigue tests are conducted under R = −1, 0, and 0.1 at 430°C.The dynamic recrystallization is observed, resulting in the cyclic softening behavior.A fatigue life prediction model considering the strain ratio is proposed at 430°C. [ABSTRACT FROM AUTHOR]

In the current work, a multiscale model was developed coupling a macro-model with the macromechanical physically based yield strength and a crystal plasticity model with micromechanical properties and realistic grain orientation based on the representative volume element. The simulation results show that the effect of microstructure on the macromechanical properties can be considered in the macro constitutive model due to a good consistency between experimental and computed results; whereas solid strengthening, grain boundaries, and dislocation density played a more crucial role than others. Besides coupling simulation and microstructure by EBSD, the microstructure evolution can be well explained by the micromechanical model. Strain is related to the grain orientation, leading to inhomogeneous deformation, forming the various Schmid factor and slip systems. A plastic strain occurs close to the grain boundaries and declines into the grain, resulting in higher kernel average misorientation (KAM) and geometry necessary dislocations (GNDs) in the grain boundaries. The higher the loading, the higher the local strain. Shear bands with around 45 degrees can be formed, resulting in crack initiation and tensile shear failure. This work has developed the guidance of structural integrity assessment and prediction of mechanical properties for the engineering material and components. [ABSTRACT FROM AUTHOR]