Tuning phase stability and short-range order through Al doping in (CoCrFeMn)100−xAlx high-entropy alloys

Abstract

For (CoCrFeMn)100-xAlx high-entropy alloys, we investigate the phase evolution with increasing Al-content (0 ≤ x ≤ 20 at.%). From first-principles theory, the Al-doping drives the alloy structurally from FCC to BCC separated by a narrow two-phase region (FCC+BCC), which is well supported by our experiments. We highlight the effect of Aldoping on the formation enthalpy and electronic structure of (CoCrFeMn)100-xAlx alloys. As chemical short-range order (SRO) in multicomponent alloys indicates the nascent local order (and entropy changes), as well as expected low-temperature ordering behavior, we use thermodynamic linear-response within density-functional theory to predict SRO and ordering transformation and temperatures inherent in (CoCrFeMn)100-xAlx. The predictions agree with our present experimental findings, and other reported ones.

First-Principles Prediction of Incipient Order in Arbitrary High-Entropy Alloys: Exemplified in Ti _0.25CrFeNiAl _x

“…On adding Al to Ti 0.25 CrFeNi, the BSF is smeared out near the Fermi energy (E F ) due to increased disorder effect. The BSF broadening can directly be related to the inverse of the electron mean free path [35]. Increased k-space smearing at E F indicates a decrease in electron mean-free path for Fig.…”

“…This deviation from the stoichiometry makes the transformation kinetics slower, which may need thousands of hours of aging time [64], but SRO in the high-T disordered phase always can occur. Considering our work is based on full electronic structure (chemical and magnetic), we are also able to capture the effects of hybridization, Fermi-surface, band-filling, Kohn anomalies, etc., on the SRO and directly "fingerprint" the origin for ordering [18,[33][34][35].…”

“…The pairwise-interchange energy S (2) µν (k; T ) in linearresponse is the chemical stability matrix referenced to the homogeneous HEA [17], which reflects the freeenergy cost for all pair fluctuations with {c i µ (k)} [18,[33][34][35]. Here, S (2) µν (k; T ) is the energy cost to exchange specific atomic pairs, with effects included to all orders in the electronic structure.…”

“…al. [18,[33][34][35] presented a DFT based thermodynamic linear-response theory that predicts all SRO pairs simultaneously (as done for displacement modes, i.e. phonons) and details the ordering behavior in HEAs [18].…”

Effect of Solution Treatment on the Shape Memory Functions of (TiZrHf)50Ni25Co10Cu15 High Entropy Shape Memory Alloy

“…It is noted that most investigations on HEAs have concentrated on structural materials for applications at low-temperature [ 2 ] or in refractory environments [ 5 ], bioapplications [ 6 ], or for applications requiring a great combination of strength and ductility [ 7 , 8 ]. In recent years, studies on HEAs have extended to non-equiatomic compositions for better desired or unique properties, such as light-weight [ 9 ], high phase stability [ 10 ], outstanding radiation resistance [ 11 ], etc. Assocaited with these newly explored properties, interpretations of fundamental mechanisms in HEAs have been investigated with both experimental and simulation techniques [ 12 , 13 , 14 , 15 , 16 ].…”