Relatively poor shape memory effect (SME) of iron-based shape memory alloys (Fe-SMAs) limits their further applications. Although recent studies have demonstrated significant SME improvements in Fe‑SMAs using various tensile-based methods, their behavior under compressive loading remains underexplored. This study investigates the SME of Fe-SMAs under quasi-static and impact compressive loading, addressing the limitations of existing impact testing apparatuses and the unclear relationship between martensitic transformation and volume resistivity during unloading and subsequent heating. A modified split Hopkinson pressure bar (SHPB) apparatus, equipped with a double momentum trap structure, was developed to ensure accurate high strain rate testing by eliminating residual stress waves and multiple loadings. Simultaneously, real‑time volume resistivity monitoring to capture the martensitic transformation during single compressive unloading and cyclic compressive training process was performed. The results revealed that the SME of Fe‑SMAs improves with increasing strain rate and that cyclic compressive training further enhances shape recovery under both quasi‑static and impact conditions. Notably, the maximum shape recovery ratio $\eta$$\eta$ is observed under the quasi-static compressive loading after the fifth cycle, reaching about 94.6 %, which is larger than the impact tensile training after sixth cycle ($\eta$$\eta$=93 %). The shape recovery under the impact was generally lower compared to tensile training due to coexistence of multiple and single variants, as confirmed by electron backscatter diffraction (EBSD) analyses. Larger grain size produced under quasi-static training results in a higher SME. This study provides insights into the compressive training mechanisms of Fe-SMAs, contributing to the optimization of SME for diverse loading applications.

中文翻译：

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准静态和冲击压缩载荷下 Fe-Mn-Si 基形状记忆合金的马氏体相变和形状记忆行为

铁基形状记忆合金 （Fe-SMA） 的形状记忆效应 （SME） 相对较差，限制了其进一步应用。尽管最近的研究表明，使用各种基于拉伸的方法在 Fe-SMA 中实现了 SME 的显著改善，但它们在压缩载荷下的行为仍未得到充分探索。本研究研究了准静态和冲击压缩载荷下 Fe-SMAs 的 SME，解决了现有冲击试验设备的局限性以及卸载和随后加热过程中马氏体转变与体积电阻率之间不明确的关系。开发了一种改进的分体式霍普金森压力棒 （SHPB） 装置，配备双动量陷阱结构，通过消除残余应力波和多重载荷来确保准确的高应变率测试。同时，进行了实时体积电阻率监测，以捕捉单次压缩卸载和循环压缩训练过程中的马氏体转变。结果表明，Fe-SMAs 的 SME 随着应变率的增加而提高，并且循环压缩训练进一步增强了准静态和冲击条件下的形状恢复。值得注意的是，在第 5 次循环后的准静态压缩载荷下观察到最大形状恢复率 $\eta$ ，达到约 94.6 %，大于第 6 次循环后的冲击拉伸训练 （ $\eta$ =93 %）。电子背散射衍射 （EBSD） 分析证实，与拉伸训练相比，冲击下的形状恢复通常较低，因为多个变体和单个变体共存。在准静态训练下产生的较大晶粒尺寸会导致更高的 SME。 本研究提供了对 Fe-SMA 压缩训练机制的见解，有助于优化 SME 以用于各种载荷应用。