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<p>The study investigated the microstructural and grain boundary evolution of a 740H nickel-based alloy with 5-15% deformation after cold rolling, during the electro-pulse treatment (EPT) process at 750-950&#xa0;°C. The results show that, under the same EPT conditions, grain size decreases with increasing deformation. For the same deformation, grain size increases with higher EPT temperature or longer treatment time. At 10% reduction, the smallest grain size (16.43&#xa0;μm) was observed at 750&#xa0;°C, while the largest (27.61&#xa0;μm) occurred at 950&#xa0;°C, both smaller than the untreated sample (28.54&#xa0;μm). Regarding grain boundaries, Σ3 boundaries transitioned from annealing twins to regular boundaries after EPT, disrupting the grain boundary network. The volume fraction of Σ3 boundaries increased and then decreased with higher EPT temperature or deformation, while it continued to rise with longer treatment times. The peak volume fraction of Σ3 boundaries (63.9%) was reached at 900&#xa0;°C with 10% deformation, while the volume fraction of low Σ CSL boundaries peaked at 65.07%. Conversely, the volume fractions of Σ9 and Σ27 boundaries decreased with increased deformation, EPT temperature, or treatment time. In conclusion, EPT treatment at 900&#xa0;°C with 10% deformation is optimal for enhancing the volume fraction of Σ3 boundaries, providing a solid theoretical foundation for grain boundary engineering in nickel-based alloys.</p>

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Study on the Microstructure and Grain Boundary Evolution of Cold-Deformed 740H Nickel-Based Alloy under Pulsed Treatment

  • 期刊论文

  • 发表日期：

    2026年3月31日

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  • Saikun Gao,
  • Yaohui Song,
  • Yugui Li,
  • Juan Li,
  • Yibo Lu,
  • Huaying Li,
  • Yurong Guo

摘要

The study investigated the microstructural and grain boundary evolution of a 740H nickel-based alloy with 5-15% deformation after cold rolling, during the electro-pulse treatment (EPT) process at 750-950 °C. The results show that, under the same EPT conditions, grain size decreases with increasing deformation. For the same deformation, grain size increases with higher EPT temperature or longer treatment time. At 10% reduction, the smallest grain size (16.43 μm) was observed at 750 °C, while the largest (27.61 μm) occurred at 950 °C, both smaller than the untreated sample (28.54 μm). Regarding grain boundaries, Σ3 boundaries transitioned from annealing twins to regular boundaries after EPT, disrupting the grain boundary network. The volume fraction of Σ3 boundaries increased and then decreased with higher EPT temperature or deformation, while it continued to rise with longer treatment times. The peak volume fraction of Σ3 boundaries (63.9%) was reached at 900 °C with 10% deformation, while the volume fraction of low Σ CSL boundaries peaked at 65.07%. Conversely, the volume fractions of Σ9 and Σ27 boundaries decreased with increased deformation, EPT temperature, or treatment time. In conclusion, EPT treatment at 900 °C with 10% deformation is optimal for enhancing the volume fraction of Σ3 boundaries, providing a solid theoretical foundation for grain boundary engineering in nickel-based alloys.