Tunable chemical complexity to control atomic diffusion in alloys

Abstract

In this paper we report a new fundamental understanding of chemically-biased diffusion in Ni-Fe random alloys that is tuned/ controlled by the intrinsic quantifiable chemical complexity. Development of radiation-tolerant alloys has been a long-standing challenge. Here we show how intrinsic chemical complexity can be utilized to guide the atomic diffusion and suppress radiation damage. The influence of chemical complexity is shown by the example of interstitial atom (IA) diffusion that is the most important defect in radiation effects. We use μs-scale molecular dynamics to reveal sluggish diffusion and percolation of IAs in concentrated Ni-Fe alloys. We develop a mean field diffusion model to take into account the effect of migrating defect energy properties on diffusion percolation, which is verified by a new kinetic Monte Carlo approach addressing detailed processes. We demonstrate that the local variations in the ground state energy of IA configurations in alloys, reflecting the chemical difference between alloying components, drives the percolation effects for atomic diffusion. Percolation, chemically-biased and sluggish diffusion are phenomena that are directly related to the chemical complexity intrinsically to multicomponent alloys.npj Computational Materials (2020) 6:38 ; https://doi.

Diffusion-mediated chemical concentration variation and void evolution in ion-irradiated NiCoFeCr high-entropy alloy

“…This can potentially guide the design of HEAs deviating from near-equimolar ratios. Osetsky et al [50] have recently discussed how to enhance diffusion percolation effects in concentrated alloys.…”

Estimating linear mass transport coefficients in solid solutions via correlation splitting and a law of total diffusion

“…where the first equality is similar to Green-Kubo formulas [27,28] and symmetry is formally recovered in the second equality. Expressions in (6) are the cornerstone of variational approaches to mass transport [27][28][29] and serve here the purpose of improving kMC estimations via correlation splitting and conditioning.…”

“…In crystalline solids, atomic transport is mediated by defects [3,4], most often by vacancies exchanging with neighboring substitutional atoms. Interstitial atoms jumping to adjacent interstitial sites also contribute to atomic diffusion, in irradiated alloys especially [5,6]. Usually, atomic hops are thermally activated processes occurring at rates that are well predicted by transition state theory and its extensions [7].…”

Tunable Chemical Disorder in Concentrated Alloys: Defect Physics and Radiation Performance

“…While dilute alloys appear near the corners of phase diagrams, SP-CSAs are composed of multiple elements, rendering irrelevant the differences between solvents and solutes. ,,, The wide variety of elemental diversity sets CSAs apart from traditional solvent–solute alloys, allows fundamental understanding at the levels of electrons and atoms, ,, and offers tunability of alloy properties. Although the maximum compositional disorder occurs at the equiatomic composition, the maximum chemical complexity depends on the coupling strengths of alloying chemical species involving local electron, magnetic, and phonon interactions, which may not occur at the equiatomic composition. ,, …”

“…Single-phase concentrated solid-solution alloys (SP-CSAs) are a unique group of CCAs. These chemically complex CSAs, including medium-entropy alloys (MEAs, e.g., with three alloying elements) and high-entropy alloys (HEAs, − commonly containing five or more alloying elements), form random solid solutions on simple crystalline lattices, such as body-centered cubic (bcc), hexagonal close-packed (hcp), or face-centered cubic (fcc) structures. ,,− The continuous discovery of many unusual and exciting properties in CCAs (e.g., strong phase stability, exceptional low-temperature toughness and high-temperature strength, improved radiation tolerance, outstanding superconductivity, and super-paramagnetism) has attracted enormous awareness and unlocked innovative frontiers in materials research. − ,− The guided design and predictive discovery of advanced structural materials are key to implementing future technologies, and this groundbreaking arena is inspiring worldwide research to identify innovative design principles and new materials with targeted structural and functional properties.…”