Formation of ordered/disordered nanoparticles in FCC high entropy alloys

Shun, Tao-Tsung; Hung, Cheng-Hsin; Lee, Che-Fu

doi:10.1016/j.jallcom.2009.12.071

Cited by 177 publications

(57 citation statements)

References 15 publications

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“…Figure 22 shows the calculated mole fraction of equilibrium phases at various temperatures in the non-equiatomic Al 0.3 CoCrFeMo 0.1 Ni senary alloy. The predicted single Fcc phase (labeled as FCC_L12) agrees well the experimental information provided by Shun et al [46] that only Fcc was observed in the as-cast state.…”

Section: Discussionsupporting

confidence: 87%

TCHEA1: A Thermodynamic Database Not Limited for “High Entropy” Alloys

Mao

Chen²,

Chen³

2017

J. Phase Equilib. Diffus.

124

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In this paper we report a thermodynamic database which was developed by using the CALPHAD approach. The TCHEA1 database includes 15 chemical elements (Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Ta, Ti, V, W and Zr). It is suitable for the study of Bcc and Fcc HEA systems. The database is constructed based on the thermodynamic assessment of all binary systems and many key ternary systems where almost all possible metastable and stable phases are considered. It is extensively demonstrated in the present work that TCHEA1 gives satisfactory prediction on the phase equilibria in various HEA systems (quaternary to ennead) and wide temperature ranges (liquidus to subsolidus). Thermodynamic stability calculations of simple solid solutions (Bcc and Fcc) and intermetallics (sigma, Laves, l-phase etc.) are validated against the available experimental information in as-cast or as-annealed state. Such CALPHAD database focusing on the modelling of Gibbs energy rather than entropy makes reliable predictions of thermodynamic equilibrium and phase transformation, no matter whether the alloy/system has high entropy or not. Cases with miscibility gap in liquid and solid solutions and second-order phase transition at low temperatures are demonstrated. With the volume data included, TCHEA1 is capable to predict the density and thermal expansion coefficient of HEAs as well. This thermodynamic database is also applicable in process simulations when used together with compatible kinetic databases.

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Section: Discussionsupporting

confidence: 87%

TCHEA1: A Thermodynamic Database Not Limited for “High Entropy” Alloys

Mao

Chen²,

Chen³

2017

J. Phase Equilib. Diffus.

124

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“…As most of the investigated alloys contain at least three or four of the elements that were also present in Cantor's CoCrFeMnNi alloy, it is not surprising that microstructures consisting predominantly of fcc solid solution phases of these elements were frequently obtained [2,10,11]. However, they also exhibited spinodal decomposition [2,10] and/or the presence of ordered phases/particles [2,11], and were not true single-phase microstructures.…”

Section: Introductionmentioning

confidence: 99%

Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys

et al. 2013

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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, 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 the 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.). Our experimental results combined with the thermodynamic analyses suggest that, in general, enthalpy and non-configurational entropy have greater 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 thermodynamically stable single-phase solid solutions.

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“…A single solid solution has only been obtained in a very limited number of high entropy alloys [7][8][9][10] and is furthermore not the best option for good mechanical properties. Over the last years it has been found that a two phase microstructure like in Ni-based super alloys implies better mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

On the Path to Optimizing the Al-Co-Cr-Cu-Fe-Ni-Ti High Entropy Alloy Family for High Temperature Applications

Manzoni

Singh

Daoud

et al. 2016

Entropy

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Abstract:The most commonly investigated high entropy alloy, AlCoCrCuFeNi, has been chosen for optimization of its microstructural and mechanical properties by means of compositional changes and heat treatments. Among the different available optimization paths, the decrease of segregating element Cu, the increase of oxidation protective elements Al and Cr and the approach towards a γ-γ 1 microstructure like in Ni-based superalloys have been probed and compared.

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Formation of ordered/disordered nanoparticles in FCC high entropy alloys

Cited by 177 publications

References 15 publications

TCHEA1: A Thermodynamic Database Not Limited for “High Entropy” Alloys

TCHEA1: A Thermodynamic Database Not Limited for “High Entropy” Alloys

Relative effects of enthalpy and entropy on the phase stability of equiatomic high-entropy alloys

On the Path to Optimizing the Al-Co-Cr-Cu-Fe-Ni-Ti High Entropy Alloy Family for High Temperature Applications

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