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<p>In this investigation, a single-pass hot compression method was applied to modify the as-cast microstructure of the Co<sub>12.5</sub>Cr<sub>12.5</sub>Cu<sub>12.5</sub>Fe<sub>12.5</sub>Ni<sub>37.5</sub>Si<sub>12.5</sub> high-entropy alloy (HEA) with the goal of achieving a significantly homogenized microstructure with reduced dendritic segregation. High-temperature compression tests were conducted within a thermo-mechanical window of 800-950&#xa0;°C and at a strain rate ranging from 0.01 to 10&#xa0;s⁻<sup>1</sup>, up to a maximum true strain of 0.92. The stress–strain responses showed that the flow stress increased significantly with decreasing deformation temperature and increasing strain rate. These stress variations were governed by deformation parameters (temperature, strain-rate, and net-strain) along with precipitate coarsening effects. To capture and predict the alloy’s deformation characteristics, a constitutive analyis based on the Arrhenius-type equation was implemented in combination with a three-dimensional processing map. The model estimated a strain-hardening exponent of 4.329 and an average activation energy for hot deformation of 425&#xa0;kJ/mol. This value is higher than that reported for conventional FCC alloys (~&#xa0;250-350&#xa0;kJ/mol) and CoCrFeNi-based HEAs (~&#xa0;300-400&#xa0;kJ/mol), indicating increased resistance to deformation due to severe lattice distortion,&#xa0;multicomponent interactions, and presence of Ni-Si stregthening phase. Workability analysis using the modified dynamic material model (MDMM) revealed that power dissipation efficiency (PDE) progressively increased with strain, reaching about 60% at a true strain of 0.92. The maximum fraction of dynamically recrystallized grains (~&#xa0;81%) was obtained at 900&#xa0;°C with a strain-rate of 0.1&#xa0;s⁻<sup>1</sup>, demonstrating that these deformation parameters are particularly favorable for converting the dendritic as-cast structure into a refined and homogenized microstructure.</p>

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Investigations on Flow Behavior and Microstructural Evolution of a Co-Cr-Cu-Fe-Ni-Si High-Entropy Alloy under Hot Compression: Modeling and Workability Analysis

  • 期刊论文

  • 发表日期：

    2026年6月18日

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  • Saket Kumar,
  • Nitish Raja,
  • Anil Kumar,
  • Santosh Kumar Tamang,
  • Manoj Chopkar

摘要

In this investigation, a single-pass hot compression method was applied to modify the as-cast microstructure of the Co12.5Cr12.5Cu12.5Fe12.5Ni37.5Si12.5 high-entropy alloy (HEA) with the goal of achieving a significantly homogenized microstructure with reduced dendritic segregation. High-temperature compression tests were conducted within a thermo-mechanical window of 800-950 °C and at a strain rate ranging from 0.01 to 10 s⁻1, up to a maximum true strain of 0.92. The stress–strain responses showed that the flow stress increased significantly with decreasing deformation temperature and increasing strain rate. These stress variations were governed by deformation parameters (temperature, strain-rate, and net-strain) along with precipitate coarsening effects. To capture and predict the alloy’s deformation characteristics, a constitutive analyis based on the Arrhenius-type equation was implemented in combination with a three-dimensional processing map. The model estimated a strain-hardening exponent of 4.329 and an average activation energy for hot deformation of 425 kJ/mol. This value is higher than that reported for conventional FCC alloys (~ 250-350 kJ/mol) and CoCrFeNi-based HEAs (~ 300-400 kJ/mol), indicating increased resistance to deformation due to severe lattice distortion, multicomponent interactions, and presence of Ni-Si stregthening phase. Workability analysis using the modified dynamic material model (MDMM) revealed that power dissipation efficiency (PDE) progressively increased with strain, reaching about 60% at a true strain of 0.92. The maximum fraction of dynamically recrystallized grains (~ 81%) was obtained at 900 °C with a strain-rate of 0.1 s⁻1, demonstrating that these deformation parameters are particularly favorable for converting the dendritic as-cast structure into a refined and homogenized microstructure.