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<p>The need to integrate an Integrated Computational Materials Engineering (ICME) framework for complex concentrated alloys represents a critical requirement for advancing future materials science and technology. In this context, the implementation of small-scale manufacturing routes is essential as an experimental validation pathway for conceptual alloy design, thereby enabling the strengthening and calibration of computational tools such as machine learning and CALPHAD. The present work investigates the microstructural evolution and mechanical response of the complex concentrated alloy (CCA) Fe₅₂₋ₓNi₂₆TiₓCr₁₈Cu₄ (x = 1–2 at%), fabricated via powder metallurgy under argon atmosphere sintering. The main objective is to evaluate the phase stability and solid-solution integration of the constituent elements, as well as their evolution over a sintering period of two hours. The compositional system was designed to maintain an austenitic matrix with a controlled stacking fault energy (SFE), enabling the activation of mechanical twinning as a secondary plasticity mechanism. This behavior was analyzed through CALPHAD thermodynamic simulations and two machine learning approaches. The microstructural evolution was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) elemental mapping, and X-ray diffraction (XRD). Additionally, the mechanical response was evaluated at both submicrometric and micrometric scales using nanoindentation and microhardness tests. The results revealed an austenitic matrix containing Cr-, Fe-, and Ti-rich clusters. Fe clusters were distributed throughout the alloy, exhibiting interrupted radial diffusion behavior. In the vicinity of Fe and Cr clusters, the presence of the sigma (σ) phase was also identified. Nanoindentation creep tests showed that the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy exhibits stronger solid-solution strengthening compared to Fe₅₁Ni₂₆Ti₁Cr₁₈Cu₄, due to a greater incorporation of Fe, Cu, and Ti into the austenitic matrix. Regarding strain-rate sensitivity, the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy displayed lower sensitivity (m = 0.0167), attributed to effective solid-solution strengthening, whereas Fe₅₁Ni₂₆Ti₁Cr₁₈Cu₄ exhibited a dual-mechanism behavior. Initially, it showed high strain-rate sensitivity (m = 0.1125), which later decreased to m = 0.0354, indicating the activation of a secondary strengthening mechanism that limits dislocation mobility. Conversely, microhardness results indicated that the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy exhibited lower overall hardness, attributed to the weakening of Fe clusters within the compositional system, which facilitated enhanced matrix strengthening as observed through nanoindentation. The load–displacement (P–h) curves revealed the presence of pop-in events, which at low loads were attributed to dislocation activation, and at higher loads to secondary mechanisms such as solid-solution strengthening, heterogeneous dislocation activation and glide, and, in the case of the CCA2 alloy, the possible activation of nanotwinning due to its local stacking fault energy of 32.2&#xa0;mJ/m² within the austenitic matrix.</p>

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Study of microstructural evolution and solid-solution strengthening in a Fe₅₂₋ₓNi₂₆TiₓCr₁₈Cu₄ (x = 1–2 at%) complex concentrated alloy: computational simulation and experimental validation

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Manuel Cabrera,
  • Diego Suazo,
  • Javiera Contreras-Cerón,
  • Carlos Campos,
  • Sergio Sauceda,
  • Nicolás Canales,
  • Cristóbal Montalba,
  • Angelo Oñate

摘要

The need to integrate an Integrated Computational Materials Engineering (ICME) framework for complex concentrated alloys represents a critical requirement for advancing future materials science and technology. In this context, the implementation of small-scale manufacturing routes is essential as an experimental validation pathway for conceptual alloy design, thereby enabling the strengthening and calibration of computational tools such as machine learning and CALPHAD. The present work investigates the microstructural evolution and mechanical response of the complex concentrated alloy (CCA) Fe₅₂₋ₓNi₂₆TiₓCr₁₈Cu₄ (x = 1–2 at%), fabricated via powder metallurgy under argon atmosphere sintering. The main objective is to evaluate the phase stability and solid-solution integration of the constituent elements, as well as their evolution over a sintering period of two hours. The compositional system was designed to maintain an austenitic matrix with a controlled stacking fault energy (SFE), enabling the activation of mechanical twinning as a secondary plasticity mechanism. This behavior was analyzed through CALPHAD thermodynamic simulations and two machine learning approaches. The microstructural evolution was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) elemental mapping, and X-ray diffraction (XRD). Additionally, the mechanical response was evaluated at both submicrometric and micrometric scales using nanoindentation and microhardness tests. The results revealed an austenitic matrix containing Cr-, Fe-, and Ti-rich clusters. Fe clusters were distributed throughout the alloy, exhibiting interrupted radial diffusion behavior. In the vicinity of Fe and Cr clusters, the presence of the sigma (σ) phase was also identified. Nanoindentation creep tests showed that the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy exhibits stronger solid-solution strengthening compared to Fe₅₁Ni₂₆Ti₁Cr₁₈Cu₄, due to a greater incorporation of Fe, Cu, and Ti into the austenitic matrix. Regarding strain-rate sensitivity, the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy displayed lower sensitivity (m = 0.0167), attributed to effective solid-solution strengthening, whereas Fe₅₁Ni₂₆Ti₁Cr₁₈Cu₄ exhibited a dual-mechanism behavior. Initially, it showed high strain-rate sensitivity (m = 0.1125), which later decreased to m = 0.0354, indicating the activation of a secondary strengthening mechanism that limits dislocation mobility. Conversely, microhardness results indicated that the Fe₅₀Ni₂₆Ti₂Cr₁₈Cu₄ alloy exhibited lower overall hardness, attributed to the weakening of Fe clusters within the compositional system, which facilitated enhanced matrix strengthening as observed through nanoindentation. The load–displacement (P–h) curves revealed the presence of pop-in events, which at low loads were attributed to dislocation activation, and at higher loads to secondary mechanisms such as solid-solution strengthening, heterogeneous dislocation activation and glide, and, in the case of the CCA2 alloy, the possible activation of nanotwinning due to its local stacking fault energy of 32.2 mJ/m² within the austenitic matrix.