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<p>In ATI 718Plus, the <i>γ</i>′/<i>γ</i>″ coprecipitation phases with diverse morphologies effectively prevents the <i>γ</i>′ phase from overaging during slow cooling after solution treatment. The deformation behavior and mechanism of the <i>γ</i>′/<i>γ</i>″ coprecipitation phase at atomic scale still need further study. Thus, molecular dynamics simulations are carried out to investigate the effect of <i>γ</i>′ precipitation phase orientation ([001], [011], [111], and [112]) on the elastic constants, tensile properties, and low-cycle fatigue properties of <i>γ</i>′/<i>γ</i>″ coprecipitation models. The deformation behaviors and mechanisms of <i>γ</i>′/<i>γ</i>″ coprecipitation models are analyzed in detail. The results demonstrate that all <i>γ</i>′/<i>γ</i>″ 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 (<i>N</i> = 23), dislocations begin to form in the <i>γ</i>″ precipitation phase, causing a secondary reduction in cyclic stress. The extrusion of defect meshes into the <i>γ</i>′ 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 <i>γ</i>′/<i>γ</i>″ coprecipitation phases in ATI 718Plus superalloys, offering valuable theoretical guidance for optimizing the performance of the 718Plus alloy.</p>

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

  • 期刊论文

  • 发表日期：

    2025年11月2日

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  • Longlong Yang,
  • Kun Sun,
  • Cheng Chen,
  • Feng Dang

摘要

In ATI 718Plus, the γ′/γ″ coprecipitation phases with diverse morphologies effectively prevents the γ′ phase from overaging during slow cooling after solution treatment. The deformation behavior and mechanism of the γ′/γ″ coprecipitation phase at atomic scale still need further study. Thus, molecular dynamics simulations are carried out to investigate the effect of γ′ precipitation phase orientation ([001], [011], [111], and [112]) on the elastic constants, tensile properties, and low-cycle fatigue properties of γ′/γ″ coprecipitation models. The deformation behaviors and mechanisms of γ′/γ″ coprecipitation models are analyzed in detail. The results demonstrate that all γ′/γ″ 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 γ″ precipitation phase, causing a secondary reduction in cyclic stress. The extrusion of defect meshes into the γ′ 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 γ′/γ″ coprecipitation phases in ATI 718Plus superalloys, offering valuable theoretical guidance for optimizing the performance of the 718Plus alloy.