Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

Abstract

Keywords:High entropy alloy Density functional theory Monte Carlo Short-range order Ni based alloys a b s t r a c t The aim of this study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. According to our study, the salient features for the ternary alloy are a negative SRO parameter between Ni-Cr and a positive between CrCr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni-Cr and Ni-Fe pairs and positive for Cr-Cr and Fe-Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. The predicted SRO has an impact on point-defect energetics, electron-phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.

Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

“…Short-range order is not rare in conventional alloys and it has obvious effect on the physical properties and materials performance [22][23][24]. Due to the chemical complexity, SRO is expected in HEAs and was predicted by density-functional theory recently [25,26]. However, no direct experimental evidence of SRO in HEAs has been reported.…”

“…Effects of SRO on the electrical resistivity of alloys have been studied theoretically and experimentally before [24,26,39]. For example, resistivity increases by 20-30% with the formation of SRO in NiCu alloys [42], which is not as markedly in NiCoCr compared with binary NiCo.…”

Lattice Distortions in the FeCoNiCrMn High Entropy Alloy Studied by Theory and Experiment

“…Density-functional-theory (DFT) calculations for FeCoNiCr and FeCoNi revealed that electronic charge transfer causes a local atomic pressure on the individual constituents, which could result in local volume fluctuations [19]. Further DFT studies revealed strong element-specific magnetic moment fluctuations in fcc FeCoNiCr, which are ultimately rooted in local electronic structure effects [20][21][22]. In particular anti-ferromagnetic Cr plays a crucial role [20].…”

Influence of gradual replacement of aluminum for copper in FeCrCoNiCu alloys

“…For some multicomponent alloys, the forming of intermetallic or even metallic glasses makes the role of mixing entropy questionable. In the past decade [5][6][7][8][9][10][11][12][13], some elements had been shown to help form the face centered cubic solid-solution phases, such as copper, and nickel, on the contrary, aluminum and chromium favour the forming of body centered cubic phases. Recently, a six-component high entropy alloy system of CoCrFeNiCu x Al 1-x has been explored and effects of lattice distortion on the phase transformation of the as-cast alloys have been studied [14].…”