Design of Refractory High-Entropy Alloys

• Published in: JOM (1989) Vol. 67; no. 11; pp. 2653 - 2669
• Main Authors: Gao, M. C., Carney, C. S., Doğan, Ö. N., Jablonksi, P. D., Hawk, J. A., Alman, D. E.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.11.2015; Springer Nature B.V; Springer
• Subjects: Alloys; BCC structure; CALPHAD; Chemistry/Food Science; Decomposition; Earth Sciences; Engineering; Entropy; Environment; high-entropy alloys; MATERIALS SCIENCE; phase diagram; Physics; refractory metals; Solids; Studies; Temperature; Thermodynamics; CALPHAD Approach; Atomic Size Difference; Total Entropy; Coarse Dendrite; Miedema Model
• ISSN: 1047-4838; 1543-1851
• DOI: 10.1007/s11837-015-1617-z

This report presents a design methodology for refractory high-entropy alloys with a body-centered cubic (bcc) structure using select empirical parameters (i.e., enthalpy of mixing, atomic size difference, Ω-parameter, and electronegativity difference) and CALPHAD approach. Sixteen alloys in equimolar compositions ranging from quinary to ennead systems were designed with experimental verification studies performed on two alloys using x-ray diffraction, energy-dispersive spectroscopy, and scanning electron microscopy. Two bcc phases were identified in the as-cast HfMoNbTaTiVZr, whereas multiple phases formed in the as-cast HfMoNbTaTiVWZr. Observed elemental segregation in the alloys qualitatively agrees with CALPHAD prediction. Comparisons of the thermodynamic mixing properties for liquid and bcc phases using the Miedema model and CALPHAD are presented. This study demonstrates that CALPHAD is more effective in predicting HEA formation than empirical parameters, and new single bcc HEAs are suggested: HfMoNbTiZr, HfMoTaTiZr, NbTaTiVZr, HfMoNbTaTiZr, HfMoTaTiVZr, and MoNbTaTiVZr.