Microstructural development in equiatomic multicomponent alloys
01 Jul 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing (Elsevier)-Vol. 375, pp 213-218
TL;DR: In this paper, it was shown that the confusion principle does not apply, and other factors are more important in promoting glass formation of late transition metal rich multicomponent alloys.
Abstract: Multicomponent alloys containing several components in equal atomic proportions have been manufactured by casting and melt spinning, and their microstructures and properties have been investigated by a combination of optical microscopy, scanning electron microscopy, electron probe microanalysis, X-ray diffractrometry and microhardness measurements. Alloys containing 16 and 20 components in equal proportions are multiphase, crystalline and brittle both as-cast and after melt spinning. A five component Fe20Cr20Mn20Ni20Co20 alloy forms a single fcc solid solution which solidifies dendritically. A wide range of other six to nine component late transition metal rich multicomponent alloys exhibit the same majority fcc primary dendritic phase, which can dissolve substantial amounts of other transition metals such as Nb, Ti and V. More electronegative elements such as Cu and Ge are less stable in the fcc dendrites and are rejected into the interdendritic regions. The total number of phases is always well below the maximum equilibrium number allowed by the Gibbs phase rule, and even further below the maximum number allowed under non-equilibrium solidification conditions. Glassy structures are not formed by casting or melt spinning of late transition metal rich multicomponent alloys, indicating that the confusion principle does not apply, and other factors are more important in promoting glass formation.
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TL;DR: High entropy alloys (HEAs) are barely 12 years old as discussed by the authors, and the field has stimulated new ideas and inspired the exploration of the vast composition space offered by multi-principal element alloys.
4,693 citations
Cites background from "Microstructural development in equi..."
...The CoCrFeMnNi alloy is singlephase FCC, even though 3 of the constituent elements are BCC at Tm (Cr, Mn, Fe) and only 2 are FCC (Co, Ni)....
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...The expansive range of new alloys and alloy systems offered by the interior regions of multi-principal element phase diagrams is a central idea in early MPEA publications [1,6,20]....
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...The second test of the high entropy effect systematically substitutes, one element at a time, 4 of the 5 elements in the CoCrFeMnNi [169]....
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...Five of these 9 elements are in the ‘Cantor alloy’ (CoCrFeMnNi) first reported in 2004 [1]....
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...The first results onmulti-component [1] and high entropy [2e6] crystalline alloys were published in 2004, about 12 years ago....
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TL;DR: The concept of high entropy introduces a new path of developing advanced materials with unique properties, which cannot be achieved by the conventional micro-alloying approach based on only one dominant element as mentioned in this paper.
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TL;DR: This work examined a five-element high-entropy alloy, CrMnFeCoNi, which forms a single-phase face-centered cubic solid solution, and found it to have exceptional damage tolerance with tensile strengths above 1 GPa and fracture toughness values exceeding 200 MPa·m1/2.
Abstract: High-entropy alloys are equiatomic, multi-element systems that can crystallize as a single phase, despite containing multiple elements with different crystal structures. A rationale for this is that the configurational entropy contribution to the total free energy in alloys with five or more major elements may stabilize the solid-solution state relative to multiphase microstructures. We examined a five-element high-entropy alloy, CrMnFeCoNi, which forms a single-phase face-centered cubic solid solution, and found it to have exceptional damage tolerance with tensile strengths above 1 GPa and fracture toughness values exceeding 200 MPa·m(1/2). Furthermore, its mechanical properties actually improve at cryogenic temperatures; we attribute this to a transition from planar-slip dislocation activity at room temperature to deformation by mechanical nanotwinning with decreasing temperature, which results in continuous steady strain hardening.
3,704 citations
TL;DR: In this article, an equiatomic CoCrFeMnNi high-entropy alloy, which crystallizes in the face-centered cubic (fcc) crystal structure, was produced by arc melting and drop casting.
2,181 citations
TL;DR: In this article, the factors of the atomic size difference Delta and the enthalpy of mixing ΔH mιx of the multi-component alloys were summarized from the literatures.
Abstract: The factors of the atomic size difference Delta and the enthalpy of mixing ΔH mιx of the multi-component alloys were summarized from the literatures. The formation zones of solid-solution phases, intermediate phases, and bulk metallic glasses were determined and the validity was verified by experimental results. For forming the solid solution, the alloys should have high entropy of mixing, lower Delta, and not too negative and positive enthalpy of mixing.
1,936 citations
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