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<p>Iron-based shape memory alloy FeMnAlNiTi that exhibits over 400&#xa0;°C temperature window of superelasticity and near-zero temperature dependence of transformation stress has garnered significant attention in the scientific community. Presence of nanoprecipitates is crucial to the functionality of this SMA, and we present a direct link between the degree of ordering of the precipitates, spinodal modulation and superelastic functionality. Upon quenching from 1225&#xa0;°C, the microstructure spontaneously decomposes into BCC matrix and DO<sub>3</sub> precipitates, both of which exhibit spinodal modulation. Prolonged aging of up to 200&#xa0;h at 200&#xa0;°C increases the degree of order of the precipitates as the modulated domains are annealed. However, no changes were detected in the precipitates' size or area fraction, ruling out the possibility of precipitate coarsening or nucleation. Concomitantly, the composition of the BCC matrix remains unchanged and continues to exhibit spinodal modulation with a wavelength of 1.13&#xa0;nm to 1.24&#xa0;nm. Finally, it is demonstrated that ultrahigh transformation stress of about 1.4 GPa can be attained along with an exponential decrease in the specific damping capacity and a consequent increase in the functional fatigue resistance.</p>

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Effect of Atomic Ordering of DO3 Precipitates on Superelasticiy and Functional Fatigue of Iron-Based Shape Memory Alloy FeMnAlNiTi

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月1日

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  • R. Sidharth,
  • H. Akamine,
  • W. Abuzaid,
  • ASK. Mohammad,
  • T. Niendorf,
  • M. Nishida,
  • H. Sehitoglu

摘要

Iron-based shape memory alloy FeMnAlNiTi that exhibits over 400 °C temperature window of superelasticity and near-zero temperature dependence of transformation stress has garnered significant attention in the scientific community. Presence of nanoprecipitates is crucial to the functionality of this SMA, and we present a direct link between the degree of ordering of the precipitates, spinodal modulation and superelastic functionality. Upon quenching from 1225 °C, the microstructure spontaneously decomposes into BCC matrix and DO3 precipitates, both of which exhibit spinodal modulation. Prolonged aging of up to 200 h at 200 °C increases the degree of order of the precipitates as the modulated domains are annealed. However, no changes were detected in the precipitates' size or area fraction, ruling out the possibility of precipitate coarsening or nucleation. Concomitantly, the composition of the BCC matrix remains unchanged and continues to exhibit spinodal modulation with a wavelength of 1.13 nm to 1.24 nm. Finally, it is demonstrated that ultrahigh transformation stress of about 1.4 GPa can be attained along with an exponential decrease in the specific damping capacity and a consequent increase in the functional fatigue resistance.