Effect of γ′ phase orientation on the mechanical properties of γ′/γ" coprecipitation phase in ATI 718Plus superalloys

LL Yang and K Sun and C Chen and F Dang, JOURNAL OF MATERIALS SCIENCE, 60, 22880-22898 (2025).

DOI: 10.1007/s10853-025-11663-2

In ATI 718Plus, the gamma '/gamma '' coprecipitation phases with diverse morphologies effectively prevents the gamma ' phase from overaging during slow cooling after solution treatment. The deformation behavior and mechanism of the gamma '/gamma '' coprecipitation phase at atomic scale still need further study. Thus, molecular dynamics simulations are carried out to investigate the effect of gamma ' precipitation phase orientation (001, 011, 111, and 112) on the elastic constants, tensile properties, and low-cycle fatigue properties of gamma '/gamma '' coprecipitation models. The deformation behaviors and mechanisms of gamma '/gamma '' coprecipitation models are analyzed in detail. The results demonstrate that all gamma '/gamma '' coprecipitation models exhibit mechanical stability. Specifically, the 001 model has the highest yield strain, which correlates with its biggest Poisson's ratio and Cauchy pressure. But a yield terrace appears on the tensile stress- strain curves of all models except the 001 model. Attributing to the various in generalized stacking-fault energy among various precipitated phases, it leads to distinct deformation mechanisms in each model. The 001 model undergoes cross-slip deformation, while the 011 model, 111 model, and 112 model experience stacking faults and extended dislocations. The 011 model has the largest cyclic stress and stress amplitude, which are consistent with its highest shear modulus, Young's modulus, and Vickers hardness. However, after a certain number of cycles (N = 23), dislocations begin to form in the gamma '' precipitation phase, causing a secondary reduction in cyclic stress. The extrusion of defect meshes into the gamma ' phase reduces the dislocation density in the 111 model and 112 model. This study provides atomic-scale insights into the mechanical properties and deformation mechanisms of gamma '/gamma '' coprecipitation phases in ATI 718Plus superalloys, offering valuable theoretical guidance for optimizing the performance of the 718Plus alloy.

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