CALPHAD ANALYSIS OF THE CRYSTALLIZATION OF THE FECOALNITA ALLOY PRODUCED BY THE WAAM METHOD
DOI:
https://doi.org/10.32782/3041-2080/2026-7-11Keywords:
CALPHAD, phase equilibrium, high-entropy alloy, wire arc additive manufacturing, Scheil crystallization, Laves phase, phase stabilityAbstract
CALPHAD calculations were performed using Thermo-Calc software (TCHEA3 database) for the FeCoAlNiTa high-entropy alloy system produced by wire arc additive manufacturing (WAAM). The primary focus of this work is the thermodynamic description of the systems, allowing for a detailed tracking of the phase precipitation sequence, changes in their chemical composition, and solidification temperature ranges. The article analyzes the influence of alloying elements on the stability of solid solutions and the formation of intermetallic compounds. By utilizing modern software and up-to-date thermodynamic databases, the work illustrates a high degree of correlation between the computational models and experimental microstructural analysis data. Scheil–Gulliver solidification modeling demonstrates that tantalum enrichment in the residual liquid phase during the final stages of solidification promotes the eutectic formation of the C14_Laves phase in the interdendritic regions. The simulation results are consistent with the experimentally observed distribution of the Ta-enriched phase along the boundaries of dendritic branches. Equilibrium thermodynamic calculations (reflecting the state of the material upon reaching full thermodynamic equilibrium) at a temperature of 1000 °C show a molar fraction of the Laves phase of approximately 2.1%. This is significantly lower than the non-equilibrium level recorded in the as-deposited state, creating a thermodynamic driving force for the partial dissolution of the Laves phase during subsequent heat treatment. Pseudo-binary sections indicate that an increase in Ta content stabilizes the C14_Laves phase, while Al strongly promotes the formation of the ordered BCC_B2 phase. The obtained results provide a thermodynamic basis for understanding phase selection during solidification, evaluating heat treatment conditions, and optimizing the composition of this alloy. The CALPHAD analysis results presented in the article not only explain existing phase transformations but also enable the purposeful optimization of the chemical composition of alloys to achieve specified mechanical and operational characteristics
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