Study of hydrogen diffusivity in equiatomic TiVZrNbHf high entropy alloy for hydrogen storage applications

High entropy alloys (HEAs) are new potential materials for hydrogen storage applications which could help with the transition towards sustainable energy sources. The rate of hydrogen kinetics is one of the material properties that is important for the storage and other hydrogen related applications. One of the limiting factors on the rate of...

High entropy alloys towards industrial applications: High-throughput screening and experimental investigation

Using the Thermo-Calc implementation of the CALPHAD approach, high-throughput screening of the Co–Cr–Fe–Mn–Ni system was implemented to find ‘islands’ of single phase FCC structure within the compositional space in order to reduce the cost of this well-studied alloy system. The screening identified a region centred around Co₁₀Cr...

Simple, controllable and environmentally friendly synthesis of FeCoNiCuZn-based high-entropy alloy (HEA) catalysts, and their surface dynamics during nitrobenzene hydrogenation

High-entropy alloys (HEAs) have rapidly become one of the hottest research topics in several fields, including materials science, corrosion technology, and catalysis because of their multiple advantages and their potential applications. In this study, using a novel straightforward electroless deposition method, multi-elemental alloys ...

Design of compositionally complex catalysts: Role of surface segregation

Besides revealing excellent mechanical properties, compositionally complex alloys are also very promising candidates for applications in heterogeneous catalysis. The opportunity provided by the tremendously large composition phase space to explore new materials and tune the materials properties in the materials design cycle is, however,...

Refractory CrMoNbWV High-Entropy Alloy Manufactured by Mechanical Alloying and Spark Plasma Sintering: Evolution of Microstructure and Properties

In this study, bulk samples of a CrMoNbWV high-entropy alloy (HEA) were obtained for the first time by spark plasma sintering (SPS) of mechanically alloyed (MA) powders at 1200 °C, 1300 °C, and 1400 °C. Microstructure evolution, phase formation as well as wear and corrosion behavior were investigated. The MA powders’ phase composition was found...

Beyond Solid Solution High-Entropy Alloys: Tailoring Magnetic Properties via Spinodal Decomposition

Since its first emergence in 2004, the high-entropy alloy (HEA) concept has aimed at stabilizing single- or dual-phase multi-element solid solutions through high mixing entropy. Here, this strategy is changed and renders such massive solid solutions metastable, to trigger spinodal decomposition for improving the alloys’ magnetic properties....

Combined Al and C alloying enables mechanism-oriented design of multi-principal element alloys: Ab initio calculations and experiments

Density functional theory (DFT) calculations were performed on Al_xC_yCoFeMnNi multi-principal element alloys (MPEAs) to understand the influence of Al and C on the stacking-fault energy (SFE). C addition to CoFeMnNi resulted in increased SFE, while it decreased in Al-alloyed CoFeMnNi. For experimental verification, Al<sub...

Dislocation-induced breakthrough of strength and ductility trade-off in a non-equiatomic high-entropy alloy

In conventional metallic materials, strength and ductility are mutually exclusive, referred to as strength-ductility trade-off. Here, we demonstrate an approach to improve the strength and ductility simultaneously by introducing micro-banding and the accumulation of a high density of dislocations in single-phase high-entropy alloys (HEAs). We...

Design of a dual-phase hcp-bcc high entropy alloy strengthened by ω nanoprecipitates in the Sc-Ti-Zr-Hf-Re system

High entropy alloys (HEAs) in the hexagonal close-packed (hcp) phase usually show poor mechanical properties. We demonstrate here, by use of ab initio simulations and detailed experimental investigations, that the mechanical properties can be improved by optimizing the microstructure. In particular we design a dual-phase HEA consisting of a...

Surface segregation in Cr-Mn-Fe-Co-Ni high entropy alloys

The reactivity of the surface of multicomponent metals such as High Entropy Alloys (HEAs) is rapidly gaining importance for corrosion and catalytic applications, but the mechanisms of surface segregation in these complex materials are poorly understood. Here we investigate with ab initio calculations the segregation thermodynamics in the...

Ab initio phase stabilities and mechanical properties of multicomponent alloys: A comprehensive review for high entropy alloys and compositionally complex alloys

Multicomponent alloys with multiple principal elements including high entropy alloys (HEAs) and compositionally complex alloys (CCAs) are attracting rapidly growing attention. The endless possibilities to explore new alloys and the hope for better combinations of materials properties have stimulated a remarkable number of research works in...

Brute force composition scanning with a CALPHAD database to find low temperature body centered Cubic High Entropy alloys

We used the Thermo-Calc High Entropy Alloy CALPHAD database to determine the stable phases of AlCrMnNbTiV, AlCrMoNbTiV, AlCrFeTiV and AlCrMnMoTi alloys from 800 to 2800 K. The concentrations of elements were varied from 1-49 atom%. A five- or six-dimensional grid is constructed, with stable phases calculated at each grid point. Thermo-Calc...

Impact of chemical fluctuations on stacking fault energies of CrCoNi and CrMnFeCoNi high entropy alloys from first principles

Medium and high entropy alloys (MEAs and HEAs) based on 3d transition metals, such as face-centered cubic (fcc) CrCoNi and CrMnFeCoNi alloys, reveal remarkable mechanical properties. The stacking fault energy (SFE) is one of the key ingredients that controls the underlying deformation mechanism and hence the mechanical performance of...

Determination of microstructural properties and its effects on hardness of FeNiCrCoAlx (x=0,20 at%) high entropy alloys

In recent years, the concept of high entropy alloys (HEAs) has gained increasing attention due to their unique compositions, microstructures and properties. High entropy alloys are defined as solid-solution alloys with 5 or more principal elements in equal or nearly equal atomic fractions with the elemental concentrations ranging from 5 – 35at%....

Long-ranged interactions in bcc NbMoTaW high-entropy alloys

We reveal that in a prototypical bcc high-entropy alloy NbMoTaW chemical interactions are long ranged and highly frustrated. We show that this is the reason that bcc solid solutions in NbMoTaW can persist to low temperatures. The ab initio-computed long-ranged interactions strongly impact characteristic thermodynamic properties and ordering...

Lattice distortions in the FeCoNiCrMn high entropy alloy studied by theory and experiment

Lattice distortions constitute one of the main features characterizing high entropy alloys. Local lattice distortions have, however, only rarely been investigated in these multi-component alloys. We, therefore, employ a combined theoretical electronic structure and experimental approach to study the atomistic distortions in the FeCoNiCrMn high...

Interplay between lattice distortions, vibrations and phase stability in NbMoTaW high entropy alloys

Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions. For BCC NbMoTaW, recent computational studies revealed, however...