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Investigating phase formations in cast AlFeCoNiCu high entropy alloys by combination of computational modeling and experiments

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Selection and thermal stability of phases are important in design of high entropy alloys (HEA). In this study, phase formations in cast AlFeCoNiCu HEA were investigated. Ab-initio molecular dynamics (AIMD) simulations were used to determine crystal structures of phases at different temperatures in equiatomic composition of AlFeCoNiCu. The AIMD results showed a possible coexistence of a face-centered cubic (fcc) phase and a bodycentered cubic (bcc) phase at the room temperature and indicated stabilization of a single fcc phase above 1070 K at the equiatomic composition of AlFeCoNiCu. The phase diagrams of AlFeCoNiCu system were calculated using a modified thermodynamic approach based on CALPHAD and Muggianu's methods. The calculated phase diagrams showed formation of the same two phases at the room temperature, and a phase transformation at about 1010 K to form a single fcc phase. The characterization experiments utilizing scanning electron microscopy (SEM), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD) confirmed the crystal structures and composition of phases determined by AIMD simulations and phase diagram calculations. High temperature XRD (HTXRD) analysis showed a significant increase in weight fraction of the fcc phase at high
temperatures confirming the predicted phase transformation.

Materials & Design 127 (2017), Pages 224–232: Freely access this article until July 28, 2017

https://authors.elsevier.com/a/1VB1Hy3Zws2Po

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