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Title: Design of Light-Weight High-Entropy Alloys

Authors:
; ; ; ; ; ; ; ORCiD logo;
Publication Date:
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1419603
Grant/Contract Number:
FE-0024054
Resource Type:
Journal Article: Published Article
Journal Name:
Entropy
Additional Journal Information:
Journal Volume: 18; Journal Issue: 12; Related Information: CHORUS Timestamp: 2018-02-05 11:24:05; Journal ID: ISSN 1099-4300
Publisher:
MDPI AG
Country of Publication:
Switzerland
Language:
English

Citation Formats

Feng, Rui, Gao, Michael, Lee, Chanho, Mathes, Michael, Zuo, Tingting, Chen, Shuying, Hawk, Jeffrey, Zhang, Yong, and Liaw, Peter. Design of Light-Weight High-Entropy Alloys. Switzerland: N. p., 2016. Web. doi:10.3390/e18090333.
Feng, Rui, Gao, Michael, Lee, Chanho, Mathes, Michael, Zuo, Tingting, Chen, Shuying, Hawk, Jeffrey, Zhang, Yong, & Liaw, Peter. Design of Light-Weight High-Entropy Alloys. Switzerland. doi:10.3390/e18090333.
Feng, Rui, Gao, Michael, Lee, Chanho, Mathes, Michael, Zuo, Tingting, Chen, Shuying, Hawk, Jeffrey, Zhang, Yong, and Liaw, Peter. 2016. "Design of Light-Weight High-Entropy Alloys". Switzerland. doi:10.3390/e18090333.
@article{osti_1419603,
title = {Design of Light-Weight High-Entropy Alloys},
author = {Feng, Rui and Gao, Michael and Lee, Chanho and Mathes, Michael and Zuo, Tingting and Chen, Shuying and Hawk, Jeffrey and Zhang, Yong and Liaw, Peter},
abstractNote = {},
doi = {10.3390/e18090333},
journal = {Entropy},
number = 12,
volume = 18,
place = {Switzerland},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.3390/e18090333

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  • Here, 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 formore » 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.« less
  • In this study, high-entropy alloys (HEAs) are new alloys that contain five or more elements in roughly-equal proportion. We present new experiments and theory on the deformation behavior of HEAs under slow stretching (straining), and observe differences, compared to conventional alloys with fewer elements. For a specific range of temperatures and strain-rates, HEAs deform in a jerky way, with sudden slips that make it difficult to precisely control the deformation. An analytic model explains these slips as avalanches of slipping weak spots and predicts the observed slip statistics, stress-strain curves, and their dependence on temperature, strain-rate, and material composition. Themore » ratio of the weak spots’ healing rate to the strain-rate is the main tuning parameter, reminiscent of the Portevin- LeChatellier effect and time-temperature superposition in polymers. Our model predictions agree with the experimental results. The proposed widely-applicable deformation mechanism is useful for deformation control and alloy design.« less
  • In this study, high-entropy alloys (HEAs) are new alloys that contain five or more elements in roughly-equal proportion. We present new experiments and theory on the deformation behavior of HEAs under slow stretching (straining), and observe differences, compared to conventional alloys with fewer elements. For a specific range of temperatures and strain-rates, HEAs deform in a jerky way, with sudden slips that make it difficult to precisely control the deformation. An analytic model explains these slips as avalanches of slipping weak spots and predicts the observed slip statistics, stress-strain curves, and their dependence on temperature, strain-rate, and material composition. Themore » ratio of the weak spots’ healing rate to the strain-rate is the main tuning parameter, reminiscent of the Portevin- LeChatellier effect and time-temperature superposition in polymers. Our model predictions agree with the experimental results. The proposed widely-applicable deformation mechanism is useful for deformation control and alloy design.« less
  • High configurational entropies have been hypothesized to stabilize solid solutions in equiatomic, multi-element alloys which have attracted much attention recently as high-entropy alloys with potentially interesting properties. To evaluate the usefulness of configurational entropy as a predictor of single-phase (solid solution) stability, we prepared five new equiatomic, quinary alloys by replacing individual elements one at a time in a CoCrFeMnNi alloy that was previously shown to be single-phase [1]. An implicit assumption here is that, if any one element is replaced by another, while keeping the total number of elements constant, the configurational entropy of the alloy is unchanged; therefore,more » the new alloys should also be single-phase. Additionally, the substitute elements that we chose, Ti for Co, Mo or V for Cr, V for Fe, and Cu for Ni, had the same room-temperature crystal structure and comparable size/electronegativity as the elements being replaced to maximize solid solubility consistent with the Hume-Rothery rules. For comparison, the base CoCrFeMnNi alloy was also prepared. After three-day anneals at elevated temperatures, multiple phases were observed in all but the base CoCrFeMnNi alloy suggesting that, by itself, configurational entropy is generally not able to override competing driving forces that also govern phase stability. Thermodynamic analyses were carried out for each of the constituent binaries in the investigated alloys (Co-Cr, Fe-Ni, Mo-Mn, etc,). Experimental results combined with the thermodynamic analyses suggest that, in general, enthalpy and non-configurational entropy have bigger influences on phase stability in equiatomic, multi-component alloys. Only when the alloy microstructure is a single-phase, approximately ideal solid solution does the contribution of configurational entropy to the total Gibbs free energy become dominant. Thus, high configurational entropy provides a way to rationalize, after the fact, why a solid solution forms (if it forms) but it is not a useful a priori predictor of which of the so-called high-entropy alloys will form single-phase solid solutions.« less