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<p>Achieving non-magnetism, ultra-high strength, excellent toughness and ductility at cryogenic temperatures is demanding, yet challenging, in the austenitic stainless steels applied as coil structures of fusion engineering. In this study, the solid solution treatment is used to regulate the microstructures and mechanical properties of a novel Fe–21Cr–15Ni–5Mn–2Mo austenitic stainless steel. Particularly, the grain growth behavior and the distributions of grain boundary characteristic are investigated to reveal their correlation with cryogenic mechanical properties and deformation mechanisms. The results show that the slow grain growth during low-temperature solution treatment is attributed to the carbonitride and Σ3<sup><i>n</i></sup> boundaries. The Σ3<sup><i>n</i></sup> boundaries effectively strengthen the material in the same way as general grain boundaries. After 1090&#xa0;°C (1363&#xa0;K) solution treatment, the steel exhibits an exceptional combination of ultra-high tensile strength at − 269&#xa0;°C (4.2&#xa0;K) of 1861.7 ± 17.8&#xa0;MPa, yield strength of 1439 ± 32.2&#xa0;MPa and elongation of 36.5 ± 2.6%. The synergistic deformation mechanisms at cryogenic temperature, including the formation of deformation twins, mobile dislocation and stacking faults, assist to enhance the strain hardening and stable plastic flow. Besides, the synergy also effectively avoids stress concentrations, which is conducive to the uniform elongation and toughness. The findings contribute to gain comprehensive understandings of cryogenic deformation mechanisms and will help to material design strategies for non-magnetic austenitic steels.</p>

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Synergistic deformation mechanisms induce ultra-high cryogenic strength and ductility in a novel non-magnetic austenitic stainless steel

  • 期刊论文

  • 发表日期：

    2025年5月26日

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  • Mengxing Zhang,
  • Changjun Wang,
  • Dangshen Ma,
  • Jianxiong Liang,
  • Boning Zhang,
  • Yu Liu,
  • Weihan Chu,
  • Chuanjun Huang

摘要

Achieving non-magnetism, ultra-high strength, excellent toughness and ductility at cryogenic temperatures is demanding, yet challenging, in the austenitic stainless steels applied as coil structures of fusion engineering. In this study, the solid solution treatment is used to regulate the microstructures and mechanical properties of a novel Fe–21Cr–15Ni–5Mn–2Mo austenitic stainless steel. Particularly, the grain growth behavior and the distributions of grain boundary characteristic are investigated to reveal their correlation with cryogenic mechanical properties and deformation mechanisms. The results show that the slow grain growth during low-temperature solution treatment is attributed to the carbonitride and Σ3n boundaries. The Σ3n boundaries effectively strengthen the material in the same way as general grain boundaries. After 1090 °C (1363 K) solution treatment, the steel exhibits an exceptional combination of ultra-high tensile strength at − 269 °C (4.2 K) of 1861.7 ± 17.8 MPa, yield strength of 1439 ± 32.2 MPa and elongation of 36.5 ± 2.6%. The synergistic deformation mechanisms at cryogenic temperature, including the formation of deformation twins, mobile dislocation and stacking faults, assist to enhance the strain hardening and stable plastic flow. Besides, the synergy also effectively avoids stress concentrations, which is conducive to the uniform elongation and toughness. The findings contribute to gain comprehensive understandings of cryogenic deformation mechanisms and will help to material design strategies for non-magnetic austenitic steels.