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Ni segregation and thermal stability of reversed austenite in a Fe–Ni alloy processed by QLT heat treatment

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Abstract

High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) were used to investigate Ni segregation and thermal stability of reversed austenite (RA) in a Fe–Ni alloy processed by quench–lamellarize–temper (QLT) heat treatment. The results show that the 77 K impact energy of the alloy increases with RA content increasing. As an austenite-stabilizing element, Ni is found to segregate in RA, though Ni is not evenly distributed within RA. The amount of segregations increases near the boundary (twice as high as the balanced content) and decreases to some extent in the center of the RA regions. Ni concentration in matrix near the boundary is lower than that in matrix far from the boundary because of Ni atom transportation from α to γ near the boundary. RA in this alloy has high heat and mechanical stability but is likely to lose its stability and transform to martensite when a mechanical load is applied at ultralow temperatures (77 K), which induces plasticity.

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Acknowledgments

This study was financially supported by the National High Technology Research and Development Program of China (No. 2007AA03Z506) and the National Basic Research Program of China (No. 2015CB654803). The authors are grateful to the staff of the Central Iron and Steel Research Institute—Thermo-Calc Software Union Open Laboratory for software support and Dr. Wang Qing-Feng from Yanshan University for valuable discussion.

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Authors and Affiliations

  1. Division of Structural Materials, Central Iron and Steel Research Institute, Beijing, 100081, China

    Tao Pan, Jing Zhu, Hang Su & Cai-Fu Yang

  2. School of Materials Science and Engineering, Tsinghua University, Beijing, 100084, China

    Tao Pan & Jing Zhu

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  1. Tao Pan
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  2. Jing Zhu
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  3. Hang Su
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  4. Cai-Fu Yang
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Correspondence to Tao Pan.

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Pan, T., Zhu, J., Su, H. et al. Ni segregation and thermal stability of reversed austenite in a Fe–Ni alloy processed by QLT heat treatment. Rare Met. 34, 776–782 (2015). https://doi.org/10.1007/s12598-015-0607-1

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  • DOI: https://doi.org/10.1007/s12598-015-0607-1

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