Superalloy ultrathin sheets have high strength, outstanding oxidation resistance, corrosion resistance and fatigue performance, and its thin-walled components occupy a considerable proportion in aeroengines. In the microforming process of aeroengine thin-walled components, the superalloy ultrathin sheet is often deformed under complex loading states and shows obvious springback. However, the forming and springback laws of superalloy ultrathin sheet in the microforming process are not clear and often affected by size effect. In addition, the existing nonlinear kinematic hardening models cannot accurately forecast the deformation and springback of superalloy ultrathin sheets. To address this issue, the cyclic shearing tests were performed to systemically explore the size effect on Bauschinger effect, permanent softening, transient hardening and work hardening stagnation of superalloy ultrathin sheets under cyclic loading states. The mechanism of size effect on cyclic mechanical response was systematically revealed through microstructure evolution combined with surface layer effect. In addition, a new multiscale cyclic hardening model was proposed based on the Y-U model and size effect on cyclic deformation behavior of superalloy ultrathin sheets. The new multiscale cyclic hardening model coupling surface layer effect and grain boundary strengthening effect was constructed by modeling the relationship between the cyclic mechanical response and size effect. Comparisons between the original Y-U model and the new proposed model on the characterization effect of shear stress-strain curves demonstrated that the proposed cyclic hardening model can accurately present the cyclic deformation behavior. To further verify the prediction capability of the proposed cyclic hardening model, the springback behavior of superalloy ultrathin sheet in U-bending test and hydroforming of seal ring was predicted via the proposed model combined with the decrease of elastic modulus and Yld2000–2d yield criterion, and the predicted results were compared with experimental ones. Comparative research revealed that the proposed cyclic hardening model can accurately describe the cyclic deformation behavior and springback of superalloy ultrathin sheets affected by size effect.

高温合金超薄板具有高强度、突出的抗氧化、耐腐蚀和疲劳性能，其薄壁部件在航空发动机中占有相当大的比重。在航空发动机薄壁构件微成形过程中，高温合金超薄板经常在复杂的加载状态下发生变形，并出现明显的回弹现象。然而，高温合金超薄板在微成形过程中的成形和回弹规律尚不明确，且常受尺寸效应影响。此外，现有的非线性随动硬化模型无法准确预测高温合金超薄板的变形和回弹。为了解决这个问题，进行了循环剪切试验以系统地探索包辛格效应、永久软化、循环加载状态下高温合金超薄板的瞬态硬化和加工硬化停滞。通过微观结构演化结合表层效应，系统地揭示了尺寸效应对循环力学响应的机理。此外，基于YU模型和高温合金超薄板循环变形行为的尺寸效应，提出了一种新的多尺度循环硬化模型。通过对循环力学响应与尺寸效应之间的关系进行建模，构建了耦合表面层效应和晶界强化效应的新型多尺度循环硬化模型。原始 YU 模型与新提出的模型对剪切应力-应变曲线表征效果的比较表明，所提出的循环硬化模型能够准确地呈现循环变形行为。为了进一步验证所提出的循环硬化模型的预测能力，通过所提出的模型结合弹性模量的降低和 Yld2000-2d 屈服准则，预测了高温合金超薄板在 U 型弯曲试验和密封环液压成形中的回弹行为，并将预测结果与实验结果进行了比较。比较研究表明，所提出的循环硬化模型可以准确描述受尺寸效应影响的高温合金超薄板的循环变形行为和回弹。为了进一步验证所提出的循环硬化模型的预测能力，通过所提出的模型结合弹性模量的降低和 Yld2000-2d 屈服准则，预测了高温合金超薄板在 U 型弯曲试验和密封环液压成形中的回弹行为，并将预测结果与实验结果进行了比较。比较研究表明，所提出的循环硬化模型可以准确描述受尺寸效应影响的高温合金超薄板的循环变形行为和回弹。为了进一步验证所提出的循环硬化模型的预测能力，通过所提出的模型结合弹性模量的降低和 Yld2000-2d 屈服准则，预测了高温合金超薄板在 U 型弯曲试验和密封环液压成形中的回弹行为，并将预测结果与实验结果进行了比较。比较研究表明，所提出的循环硬化模型可以准确描述受尺寸效应影响的高温合金超薄板的循环变形行为和回弹。并将预测结果与实验结果进行了比较。比较研究表明，所提出的循环硬化模型可以准确描述受尺寸效应影响的高温合金超薄板的循环变形行为和回弹。并将预测结果与实验结果进行了比较。比较研究表明，所提出的循环硬化模型可以准确描述受尺寸效应影响的高温合金超薄板的循环变形行为和回弹。