https://dc.engconfintl.org/cgi/viewcontent.cgi?article=1032&context=superalloys_ii

A critical review of high entropy alloys and related concepts

High-entropy alloys (HEAs) are alloys with five or more principal elements. Due to the distinct design concept, these alloys often exhibit unusual properties. Thus, there has been significant interest in these materials, leading to an emerging yet exciting new field. This paper briefly reviews some critical aspects of HEAs, including core effects, phases and crystal structures, mechanical properties, high-temperature properties, structural stabilities, and corrosion behaviors. Current challenges and important future directions are also pointed out.

https://www.tandfonline.com/doi/pdf/10.1080/21663831.2014.912690

High-Entropy Alloys: A Critical Review

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.

Solid‐Solution Phase Formation Rules for Multi‐component Alloys

Prediction of high-entropy stabilized solid-solution in multi-component alloys

Phase stability is an important topic for high entropy alloys (HEAs), but the understanding to it is very limited. The capability to predict phase stability from fundamental properties of constituent elements would benefit the alloy design greatly. The relationship between phase stability and physicochemical/thermodynamic properties of alloying components in HEAs was studied systematically. The mixing enthalpy is found to be the key factor controlling the formation of solid solutions or compounds. The stability of fcc and bcc solid solutions is well delineated by the valance electron concentration (VEC). The revealing of the effect of the VEC on the phase stability is vitally important for alloy design and for controlling the mechanical behavior of HEAs.

/pdf/effect-of-valence-electron-concentration-on-stability-of-fcc-3bvc8oeb0w.pdf

Effect of valence electron concentration on stability of fcc or bcc phase in high entropy alloys

On the elemental effect of AlCoCrCuFeNi high-entropy alloy system

Nous nous sommes proposes de determiner s'il etait possible, en remplacant Co par un element moins couteux (Mn) dans le systeme d'alliages Al-Cr-Cu-Fe-Co-Ni, de developper des alliages plus economiques avec des proprietes equivalentes ou eventuellement superieures. Dans le present travail, divers alliages equivalents contenant soit Mn soit Co ont ainsi ete elabores et compares en termes de microstructure et de proprietes. Il apparait que les additions de Mn favorisent la formation d'une structure cubique centree (cc) et inhibent la segregation de Cu dans les espaces interdendritiques. Ces modifications, en particulier la formation d'une phase cc plus resistante, conduisent a une augmentation de durete d'environ 150 a 200 unites Vickers pour les alliages contenant du Mn. De plus la mise en ordre B2 de la phase cc dans les alliages contenant du Co est inhibee par la substitution de Mn, ce qui a pour effet d'augmenter la tenacite. On trouve en outre que les alliages contenant du Mn presentent un interessant phenomene de durcissement par vieillissement a 800 °C. Ceci est particulierement vrai des alliages AlCrCuFeMnNi, Al 0,8 CrcuFeMnNi et Al 0,8 CrCuFe 1,5 MnNi, et ces alliages pourraient ainsi avoir un potentiel d'applications important pour des elements de structure et des outils destines a fonctionner a des temperatures pouvant atteindre 800 °C.

Chung-Chin Tung

Papers

On the elemental effect of AlCoCrCuFeNi high-entropy alloy system

EFFECT OF THE SUBSTITUTION OF Co BY Mn IN Al-Cr-Cu-Fe-Co-Ni HIGH-ENTROPY ALLOYS