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<p>Differential scanning calorimetry (DSC) provides macroscopic thermodynamic and kinetic information on the martensite/austenite transformation, enabling a quantitative linkage between microstructure and the temperature- and energy-scales of shape memory performance, and thus allowing a more comprehensive explanation and prediction of the shape memory behavior and repeatability of Fe-Mn-Si shape memory alloy (Fe-SMA). This study investigates the thermal and microstructural evolution of a Fe-28Mn-6Si-5Cr SMA subjected to six cycles of cyclic compressive training under both quasi-static and impact loading. DSC revealed that all characteristic transformation temperatures decreased after deformation, with the largest shifts in martensite start temperature <i>M</i><sub><i>s</i></sub> and martensite finish temperature <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(M_{\dot f}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mi>M</mi> <mrow> <mrow> <mover> <mi>f</mi> <mo>˙</mo> </mover> </mrow> </mrow> </msub> </math></EquationSource> </InlineEquation>, the clear difference between quasi-static and impact is <i>M</i><sub><i>f</i></sub>. The specific enthalpy and driving force grew rapidly during the first three quasi-static cycles but plateaued thereafter; impact loading induced a marked jump in these parameters at the second cycle, followed by minimal variation. Calculations of effective stress and internal stress showed that quasi-static training progressively lowered effective stress and internal stress, indicative of facilitated reverse transformation, while impact training maintained higher levels. Electron backscatter diffraction (EBSD) analyses demonstrated that quasi-static compression promoted pronounced martensite variant alignment after unloading, in contrast to the more random, weakly accumulated martensite under impact loading; recrystallization mapping further revealed that, by the sixth cycle, quasi-static specimens retained ∼85% substructure with ∼1.2% recrystallization, whereas impact specimens exhibited ∼60% substructure and ∼2% recrystallization, signifying earlier functional degradation.</p>

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Thermal and microstructural responses in Fe-Mn-Si shape memory alloy during rate-dependent cyclic compressive training

  • 期刊论文

  • 发表日期：

    2026年5月25日

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  • Qian Sun,
  • Bo Cao,
  • Takeshi Iwamoto

摘要

Differential scanning calorimetry (DSC) provides macroscopic thermodynamic and kinetic information on the martensite/austenite transformation, enabling a quantitative linkage between microstructure and the temperature- and energy-scales of shape memory performance, and thus allowing a more comprehensive explanation and prediction of the shape memory behavior and repeatability of Fe-Mn-Si shape memory alloy (Fe-SMA). This study investigates the thermal and microstructural evolution of a Fe-28Mn-6Si-5Cr SMA subjected to six cycles of cyclic compressive training under both quasi-static and impact loading. DSC revealed that all characteristic transformation temperatures decreased after deformation, with the largest shifts in martensite start temperature Ms and martensite finish temperature \(M_{\dot f}\) M f ˙ , the clear difference between quasi-static and impact is Mf. The specific enthalpy and driving force grew rapidly during the first three quasi-static cycles but plateaued thereafter; impact loading induced a marked jump in these parameters at the second cycle, followed by minimal variation. Calculations of effective stress and internal stress showed that quasi-static training progressively lowered effective stress and internal stress, indicative of facilitated reverse transformation, while impact training maintained higher levels. Electron backscatter diffraction (EBSD) analyses demonstrated that quasi-static compression promoted pronounced martensite variant alignment after unloading, in contrast to the more random, weakly accumulated martensite under impact loading; recrystallization mapping further revealed that, by the sixth cycle, quasi-static specimens retained ∼85% substructure with ∼1.2% recrystallization, whereas impact specimens exhibited ∼60% substructure and ∼2% recrystallization, signifying earlier functional degradation.