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<p>Fe–Cr–Ni austenitic alloys are extensively utilized in the hot-end components of nuclear light water reactors, turbine disks, and gas compressors. However, their low strength at elevated temperatures limits their engineering applications. In this study, a novel precipitation-strengthened alloy system is developed by incorporating Al and Si elements into a FeCrNi equiatomic alloy. The results indicate that the FeCrNiAl<sub><i>x</i></sub>Si<sub><i>x</i></sub> (at%, <i>x</i> = 0.1, 0.2) alloys possess heterogeneous precipitation structures that feature a micron-scale σ phase at the grain boundaries and a nanoscale ordered body-centered cube (B2) phase within the grains. An exceptional strength-ductility synergy across a wide temperature range is achieved in FeCrNiAl<sub>0.1</sub>Si<sub>0.1</sub> alloys due to grain refinement and precipitation strengthening. Notably, a yield strength of 693.83 MPa, an ultimate tensile strength of 817.55 MPa, and a uniform elongation of 18.27% are attained at 873 K. The dislocation shearing mechanism for B2 phases and the Orowan bypass mechanism for σ phase, coupled with a high density of nano-twins and stacking faults in the matrix, contribute to the excellent mechanical properties at cryogenic and ambient temperatures. Moreover, the emergence of serrated σ phase and micro-twins in the matrix plays a crucial role in the strengthening and toughening mechanisms at intermediate temperatures. This study offers a novel perspective and strategy for the development of precipitation-hardened Fe–Cr–Ni austenitic alloys with exceptional strength–ductility synergy over a broad temperature range.</p>

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Achieving the excellent intermediate-temperature strength–ductility synergy in a fine-grained FeCrNi-based medium entropy alloy with heterogeneous precipitation

  • 期刊论文

  • 发表日期：

    2025年3月26日

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  • Tianxiang Bai,
  • Tuanwei Zhang,
  • Zhiming Jiao,
  • Jinyao Ma,
  • Hui Chang,
  • Jianjun Wang,
  • Dan Zhao,
  • Shengguo Ma,
  • Zhouzhu Mao,
  • Xiaoxiao Liu,
  • Zhihua Wang

摘要

Fe–Cr–Ni austenitic alloys are extensively utilized in the hot-end components of nuclear light water reactors, turbine disks, and gas compressors. However, their low strength at elevated temperatures limits their engineering applications. In this study, a novel precipitation-strengthened alloy system is developed by incorporating Al and Si elements into a FeCrNi equiatomic alloy. The results indicate that the FeCrNiAlxSix (at%, x = 0.1, 0.2) alloys possess heterogeneous precipitation structures that feature a micron-scale σ phase at the grain boundaries and a nanoscale ordered body-centered cube (B2) phase within the grains. An exceptional strength-ductility synergy across a wide temperature range is achieved in FeCrNiAl0.1Si0.1 alloys due to grain refinement and precipitation strengthening. Notably, a yield strength of 693.83 MPa, an ultimate tensile strength of 817.55 MPa, and a uniform elongation of 18.27% are attained at 873 K. The dislocation shearing mechanism for B2 phases and the Orowan bypass mechanism for σ phase, coupled with a high density of nano-twins and stacking faults in the matrix, contribute to the excellent mechanical properties at cryogenic and ambient temperatures. Moreover, the emergence of serrated σ phase and micro-twins in the matrix plays a crucial role in the strengthening and toughening mechanisms at intermediate temperatures. This study offers a novel perspective and strategy for the development of precipitation-hardened Fe–Cr–Ni austenitic alloys with exceptional strength–ductility synergy over a broad temperature range.