TY - JOUR

T1 - Effects of heat treatment on microstructure, hardness and local structure in a compositionally complex alloy

AU - Fantin, A.

AU - Cakir, C. T.

AU - Kasatikov, S.

AU - Schumacher, G.

AU - Manzoni, A. M.

N1 - Publisher Copyright: © 2021 Elsevier B.V.

PY - 2022/1/15

Y1 - 2022/1/15

N2 - Unlike conventional alloys, high entropy alloys are characterized by one or more solid solution phase(s) without a clearly defined solvent, all element contribute to the matrix in a way that is still not entirely understood. In addition, it is not known to what extent classic thermodynamic rules can be applied to these multi-element alloys, especially concerning the question about what factor incites the matrix to undergo a phase transformation. This work tackles directly some of these aspects on a chosen alloy, Al8Cr17Co17Cu8Fe17Ni33 (at.%), which presents a high temperature single-phase γ state and a two-phase state with γ′ precipitates, above and below 900 °C, respectively. A combined investigation via microstructural observations, hardness testing, X-ray absorption and photoelectron spectroscopy was carried out above the γ′ formation temperature. Hardness values are independent of the annealing temperatures, microstructural analysis shows no phase formation and X-ray absorption spectroscopy does not reveal observable changes in neither local atomic nor electronic structure, indicating that approaching γ′ formation temperature is not influenced by atomic or electronic rearrangements. Interestingly, short-range chemical order remains quantitatively compatible at any annealing temperature in the single-phase γ state, and the observed preferred pairs Al–Cu and Al–Ni in the γ state match with the γ’ precipitates composition below 900 °C.

AB - Unlike conventional alloys, high entropy alloys are characterized by one or more solid solution phase(s) without a clearly defined solvent, all element contribute to the matrix in a way that is still not entirely understood. In addition, it is not known to what extent classic thermodynamic rules can be applied to these multi-element alloys, especially concerning the question about what factor incites the matrix to undergo a phase transformation. This work tackles directly some of these aspects on a chosen alloy, Al8Cr17Co17Cu8Fe17Ni33 (at.%), which presents a high temperature single-phase γ state and a two-phase state with γ′ precipitates, above and below 900 °C, respectively. A combined investigation via microstructural observations, hardness testing, X-ray absorption and photoelectron spectroscopy was carried out above the γ′ formation temperature. Hardness values are independent of the annealing temperatures, microstructural analysis shows no phase formation and X-ray absorption spectroscopy does not reveal observable changes in neither local atomic nor electronic structure, indicating that approaching γ′ formation temperature is not influenced by atomic or electronic rearrangements. Interestingly, short-range chemical order remains quantitatively compatible at any annealing temperature in the single-phase γ state, and the observed preferred pairs Al–Cu and Al–Ni in the γ state match with the γ’ precipitates composition below 900 °C.

KW - Compositionally complex alloys

KW - EXAFS

KW - High entropy alloys

KW - NEXAFS

KW - Short-range order

KW - HIGH-ENTROPY ALLOYS

KW - ELEMENTS

UR - http://www.scopus.com/inward/record.url?scp=85119065056&partnerID=8YFLogxK

U2 - 10.1016/j.matchemphys.2021.125432

DO - 10.1016/j.matchemphys.2021.125432

M3 - Article

AN - SCOPUS:85119065056

VL - 276

JO - Materials Chemistry and Physics

JF - Materials Chemistry and Physics

SN - 0254-0584

M1 - 125432

ER -