Miscibility gap and phonon thermodynamics of Fe-Au alloys studied by inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering

Muñoz, J. A.; Fultz, B.

doi:10.1063/1.4927178

Cited by 2 publications

(1 citation statement)

References 28 publications

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“…In the same vein, ΔS mix contributions have also been included in the calculations, albeit selectively; including ΔS mix has shown to improve the accuracy of the predicted thermodynamic quantities, such as the order-disorder phase transformation temperature and miscibility gap temperature. 3,4,[10][11][12][13][14][15] The contribution of ΔS mix has often been considered less important, largely due to its relatively smaller size compared to ΔH mix , particularly in the prediction of ordered structures. However, in the past decade, with the development of high entropy alloys (HEAs), 16,17 it is gradually becoming evident that ΔS mix might be equally important in the phase stability predictions.…”

Section: Introductionmentioning

confidence: 99%

Entropy contributions to phase stability in binary random solid solutions

et al. 2018

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High entropy alloys contain multiple elements in large proportions that make them prone to phase separation. These alloys generally have shallow enthalpy of mixing which makes the entropy contributions of similar magnitude. As a result, the phase stability of these alloys is equally dependent on enthalpy and entropy of mixing and understanding the individual contribution of thermodynamic properties is critical. In the overall vision of designing high entropy alloys, in this work, using density functional theory calculations, we elucidate the contributions of various entropies, i.e., vibrational, electronic and configurational towards the phase stability of binary alloys. We show that the contribution of electronic entropy is very small compared to the vibrational and configurational entropies, and does not play a significant role in the phase stability of alloys. The configurational and vibrational entropies can either destabilize or can collectively contribute to stabilize the solid solutions. As a result, even those systems that have negative mixing enthalpy can show phase instability, revealed as a miscibility gap; conversely, systems with positive mixing enthalpy can be phase stable due to entropic contributions. We suggest that including entropic contributions are critical in the development of theoretical framework for the computational prediction of stable, single-phase high entropy alloys that have shallow mixing enthalpies, unlike ordered intermetallics.

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