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<p>In this study, we investigated the microstructure, mechanical properties, and deformation mechanisms of a Fe35.1Co30.6Ni24.3Al6Ti4 HEA strengthened by coherent γ′ precipitates and the TRIP effect. XRD and TEM results confirmed a dual-phase FCC matrix with coherent γ′ precipitates (average size  ~ 45&#xa0;nm), exhibiting a low lattice misfit of 0.28%. EBSD analysis revealed an equiaxed grain structure ( ~ 25&#xa0;μm) without strong texture. Tensile tests demonstrated a remarkable strength–ductility balance, with the aged T4 alloy (γ′-strengthened) achieving a yield strength of 820&#xa0;MPa, ultimate tensile strength of 1120&#xa0;MPa, and fracture strain of 22.5%, representing a 355.6% (from 180 to 820 MPa) increase in yield strength compared to the matrix alloy (T0) while maintaining considerable ductility. The strengthening mechanisms were attributed to precipitation hardening from γ′ nanoparticles and TRIP-assisted strain accommodation, where stress-induced FCC to BCC phase transformation enhanced work hardening and delayed necking. Post-deformation EBSD analysis confirmed dislocation slip, grain rotation, and the formation of low-angle grain boundaries, further contributing to strain hardening. These findings provide insights into designing HEAs with superior mechanical properties through synergistic precipitation and TRIP effects.</p>

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Achieving a Good Strength–Ductility Trade-off by Introducing Coherent Secondary Phase and Transformation-Induced Plasticity Effect in a Fe35.1Co30.6Ni24.3Al6Ti4 High-Entropy Alloy

  • 期刊论文

  • 发表日期：

    2025年10月27日

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  • Peng Xiao,
  • Zhou Yang,
  • Yuqing Huang,
  • Chengqi Zhang

摘要

In this study, we investigated the microstructure, mechanical properties, and deformation mechanisms of a Fe35.1Co30.6Ni24.3Al6Ti4 HEA strengthened by coherent γ′ precipitates and the TRIP effect. XRD and TEM results confirmed a dual-phase FCC matrix with coherent γ′ precipitates (average size  ~ 45 nm), exhibiting a low lattice misfit of 0.28%. EBSD analysis revealed an equiaxed grain structure ( ~ 25 μm) without strong texture. Tensile tests demonstrated a remarkable strength–ductility balance, with the aged T4 alloy (γ′-strengthened) achieving a yield strength of 820 MPa, ultimate tensile strength of 1120 MPa, and fracture strain of 22.5%, representing a 355.6% (from 180 to 820 MPa) increase in yield strength compared to the matrix alloy (T0) while maintaining considerable ductility. The strengthening mechanisms were attributed to precipitation hardening from γ′ nanoparticles and TRIP-assisted strain accommodation, where stress-induced FCC to BCC phase transformation enhanced work hardening and delayed necking. Post-deformation EBSD analysis confirmed dislocation slip, grain rotation, and the formation of low-angle grain boundaries, further contributing to strain hardening. These findings provide insights into designing HEAs with superior mechanical properties through synergistic precipitation and TRIP effects.