Equiatomic High-entropy Alloy Research Articles

Bayesian Optimization of 7-component (AlVCrFeCoNiMo) single crystal alloy’s compositional space to optimize elasto-plastic properties from Molecular Dynamics Simulations

Abstract Exploring the vast compositional space of high-entropy alloys promises materials with superior mechanical properties much needed in industrial applications. We demonstrate on the 7-component alloy AlVCrFeCoNiMo system with randomly ordered atoms that this exploration of the compositional space can be accelerated by combining molecular dynamics simulations with Bayesian optimization. Our algorithm is tested on maximizing the shear modulus, resulting in pure Mo, an unsurprising result based on Mo’s large density. Maximizing the yield stress results in Co-, Cr- and Ni-based alloys with the optimal composition varying depending on the presence of defects within the crystal. Finally, we optimize the plastic behaviour by aiming for high stresses while minimizing the deformation fluctuations, and find that a predominantly NiMo alloy’s high lattice distortions ensure a smooth stress response. The results suggest that mechanical properties of 2- to 4-component alloys with optimized composition may be superior to those of equiatomic high-entropy alloys without short-range order.

A Study on the Structural, Wear, and Corrosion Properties of CoCuFeNiMo High-Entropy Alloy

This study investigates the structural properties, wear resistance and corrosion behavior of a CoCuFeNiMo equiatomic high-entropy alloy. The alloy was prepared using a vacuum arc melting device, and its structural properties were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Wear tests were conducted using a pin-on-disc machine against 4140 stainless steel at different loads. Corrosion behavior was evaluated through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in a 3.5wt% NaCl solution. The results indicated the presence of a major face-centered cubic (FCC) phase and a minor (µ) phase. The alloy exhibited segregation of Cu, attributed to positive mixing enthalpy. The coefficient of friction exhibited stability under lower loads but fluctuated under higher loads, possibly due to inhomogeneity in the microstructure caused by Cu segregation. Wear rates increased linearly with applied loads, indicating a direct relationship between load and wear properties. The worn surfaces displayed characteristics of mild abrasive wear, with delaminations, ploughing, and abrasive wear tracks. Pitting corrosion was observed, and the corrosion process was explained as the attack of Cl- ions leading to galvanic corrosion between different phases. In the corrosion analysis, the Ecorr value was -0.616V, and the icorr value was found to be 2.22 × 10-5 A/cm2.

Nanoparticles of MnFeNiCuBi high entropy alloy as catalyst for Fenton and photo-Fenton decomposition of p-nitrophenol

We report here preparation of an equi-atomic high entropy alloy (HEA) where Bi (hexagonal) was used along with Mn, Fe, Ni and Cu. The HEA assumed fcc structure after ball milling for 60 h of the arc melted component which was initially having multiple phases. XRD and TEM studies corroborated the HEA formation. The XPS studies of the milled sample inferred a probable formation of multicomponent oxide shells on the surface, which could generate a band gap of 1.62 eV. Hence, the present material emerged as an efficient catalyst, which could completely decompose, PNP in 60 min for Fenton and 20 min for photo-Fenton processes. When tested for four cycles, the HEA also displayed appreciable stability as a photo-Fenton catalyst. Further, the catalyst’s soft ferromagnetic nature (MS = 4.55 emu/g) contributes to its recyclability. Given the associated challenges with conventional Fe catalysts utilized in Fenton and photo-Fenton processes, this work provides an alternative as a promising catalyst for treating PNP-containing wastewater.

Impact of copper and manganese on phase transformation, microstructural development and material strength in CoCrFeNi high-entropy alloys through mechanical alloying

CoCrFeNiX (X = Cu, Mn) equiatomic high-entropy alloys (HEAs) were prepared through mechanical alloying (MA) followed by sintering at moderate temperature. The prepared HEAs were subjected to X-ray diffraction and microscope techniques to evaluate their phase evolution, microstructure, and elemental composition. Alloyed CoCrFeNiCu powder consists of two face centered cubic (FCC) phases (FCC1 and FCC2), whereas, CoCrFeNiMn powder showed a major FCC phase with a minor body centered cubic (BCC) phase. After sintering, bulk CoCrFeNiMn alloy showed only a single solid solution FCC phase, and the bulk CoCrFeNiCu still contained dual FCC phases. The elemental composition analysis revealed that both HEAs are equiatomic in composition. The average microhardness of CoCrFeNiCu and CoCrFeNiMn HEAs was 85 ± 15 HV and 147 ± 20 HV, respectively. It was observed that the presence of Cu in CoCrFeNiCu reduces the hardness of the HEA due to segregation. This study demonstrates the influence of the fifth metal on the phase evolution, microstructure, and mechanical properties of the HEAs.

Mechanical processing and thermal stability of the equiatomic high entropy alloy TiVZrNbHf under vacuum and hydrogen pressure

This study investigates the potential of nanostructuring the equiatomic high entropy alloy TiVZrNbHf by high-pressure torsion to improve its already promising hydrogen absorption properties. The detailed microstructural analysis of the material after processing demonstrates that a homogenous single-phase nanocrystalline structure can be obtained despite shear band development. Due to the metastable character of many high entropy alloys, this analysis was complemented by investigating the thermal stability of the alloy under both vacuum and hydrogen pressure. For the latter, the material was characterized via in situ X-ray diffraction during hydrogen charging at 500 °C, giving a detailed insight into the phase evolution during initial absorption and subsequent cycling. These experiments evidenced the inherent metastability of TiVZrNbHf, which resulted in its decomposition into a bcc, hcp, and C14 Laves phase under both vacuum and hydrogen atmospheres. Despite decomposition, the material retained its nanocrystalline structure under hydrogen pressure, presumably due to hydride formation, while significant grain growth occurred under vacuum. These findings deepen the understanding of the deformation and hydrogen charging behavior of this promising high entropy alloy, suggesting an approach for engineering such alloys for enhanced stability and performance, particularly in solid-state hydrogen storage applications.

Superconductivity with a high upper critical field in an equiatomic high-entropy alloy Sc–V–Ti–Hf–Nb

High-entropy alloy (HEA) superconductors have attracted significant attention due to their exceptional low-temperature mechanical and superconducting properties. We report the synthesis and thorough characterization of an equiatomic HEA superconductor with the composition Sc0.20V0.20Ti0.20Hf0.20Nb0.20, crystallizing in a body-centered cubic crystal structure (Im3m¯). Our investigation, using magnetization, transport, and heat capacity measurements, reveals the presence of weakly coupled, fully gapped superconductivity with a transition temperature of 4.17(3) K and the upper critical field exceeding the Pauli paramagnetic limit. The metallic nature, combined with a high upper critical field, positions it as a promising candidate for applications in superconducting devices.

Elevated-temperature creep properties and deformation mechanisms of a non-equiatomic FeMnCoCrAl high-entropy alloy

This study investigates the high-temperature creep behavior of a novel (Fe50Mn30Co10Cr10)91Al9 non-equiatomic high-entropy alloy (HEA) spanning the temperature range of 873–973 K and stress conditions from 50 to 90 MPa. Microstructural examinations and theoretical analyses are conducted to elucidate the performance parameter and deformation mechanisms of the HEA under sustained high-temperature conditions, providing an theoretical basis for application prospects. The results indicated that the cold-rolled and annealed alloy exhibited excellent creep resistance under conditions of 923 K/50 MPa and 873 K/50 MPa. The creep mechanism of the HEA at 923 K was identified as being primarily controlled by dislocation climb, as determined by stress exponent fitting calculations. Differing from common equiatomic HEAs, creep in these cases is controlled by solute atoms and mobile dislocations mechanisms. Microstructural characterization validated identified creep trends and deformation mechanisms, revealing diverse micro-mechanisms, such as dislocation jogs and new phase precipitation under various deformation conditions. Additionally, the 'climb-dominant mechanism model' was used to discuss the self-consistency of experimental parameters, providing in-depth insights into the contribution of elemental parameter variations to dislocation climb, as well as the reasoning behind creep performance concerning stress and temperature dependencies.

Mechanical alloying of AlCoCrFe and AlCoCrFeNi: Design and experimental evaluation of medium- and high-entropy alloy particles for cold spraying

The manufacturability of equiatomic high-entropy alloy (HEA) particles with single- and dual-phase crystal structures using the high-energy mechanical alloying (HE-MA) method was explored in this study. Following a material design-of-experiment (DoE) curriculum, particles were synthesized in a planetary mill. Milling times varied while operating under two distinct HE-MA manufacturing regimes: the conventional approach (simultaneous milling of constituent elements) and the sequential method (progressive milling with the introduction of elements in a specific order). Within the conventional regime, equiatomic AlCoCrFe and AlCoCrFeNi blends were milled, focusing on the influence of incorporating nickel (Ni) as a transient element into the base composition. This led to an equivalent particle size distribution ranging from 5 to 100 μm. Notably, the presence of Ni resulted in an increased fraction of the face-centered cubic (FCC) phase, coupled with a simultaneous reduction in grain and crystallite sizes, thereby enhancing the overall material strength. This knowledge was applied to the design and synthesis of a target equiatomic FeNiCoCrAl HEA system. In this context, individual elements were added to the starting/milled Fe + Ni alloy at four-hour intervals, in line with the sequential milling regimen. The results showed an interesting evolution: the conventionally milled AlCoCrFeNi particles exhibited a dual-phase body-centered cubic (BCC) and FCC structure, with a composition of 55% BCC and 45% FCC phase fractions, while the sequentially milled FeNiCoCrAl particles demonstrated a single-phase BCC structure after 24 h of milling.

The microstructure, mechanical compression, and electrochemical behavior of novel equiatomic CoCrMoNiW and Co-rich Co50Cr12.5Mo12.5Ni12.5W12.5 high-entropy alloys fabricated by vacuum arc remelting

In this research, we developed and analyzed novel equiatomic CoCrMoNiW and Co-rich Co50Cr12.5Mo12.5Ni12.5W12.5 high-entropy alloys (HEAs). Using FactSage, we identified dual face-centered cubic (FCC) and body-centered cubic (BCC) phases in the equiatomic HEA and a predominant FCC phase in the Co-rich HEA. The results of an elemental analysis reveal the significant presence of W and Mo in the equiatomic HEA and Co, Cr, and Ni in the Co-rich HEA. X-ray diffraction revealed dual-phase FCC and BCC structures in both HEAs, with the presence of an intermetallic μ phase. The Co-rich HEA exhibited significant compressive strain due to the prevalence of the ductile FCC phase at the expense of corrosion resistance. On the other hand, the CoCrMoNiW HEA demonstrated superior corrosion resistance comparable to those of the L605 alloy and 316 L stainless steel.

Additive manufacturing of a new non-equiatomic high-entropy alloy with exceptional strength-ductility synergy via in-situ alloying

Equiatomic high-entropy alloys (HEAs) fabricated by additive manufacturing (AM) have gained increasing attention since they present superior mechanical properties over their counterparts made by traditional synthesis routes. However, few studies have investigated AM of non-equiatomic HEAs, although this type of HEAs showing excellent mechanical properties. In this paper, we additively manufactured a novel non-equiatomic FeCoCrNi HEA via in-situ alloying 316L stainless steel and CrCoNi medium-entropy alloy. Besides the fine grain size (9 μm) and high dislocation density (3.8 × 1014 m−2), we observed unexpected high-intensity of hybrid crystal-amorphous precipitates, which have never been reported in NiCoCr-based alloys made by AM. These unique microstructures led to exceptional combination of strength (561 MPa) and elongation (41 %) exceeding those of additively manufactured equiatomic FeCoCrNi HEAs. Our observation from EBSD, TEM and atomistic simulations reveals a group of deformation mechanisms of stacking faults, deformation twins, TB-dislocation and dislocation-precipitates interactions. Our findings not only provide new insights into AM of non-equiatomic HEAs via in situ alloying, also shed lights on understanding the microstructure-properties relationship of non-equiatomic HEAs fabricated by AM.

High-Temperature Oxidation Behavior of FeCoCrNi+(Cu/Al)-Based High-Entropy Alloys in Humid Air

Previous studies showed some transition metal high-entropy alloy (HEA) compositions can have good oxidation resistance in air up to 800 °C. Four equiatomic HEAs have been developed based on FeCoCrNi with additions of Mn, Cu, Al or Al+Cu. The oxidation behavior of these HEAs was compared in humid (10 vol.% H2O) air at 800 °C for 100–500 h to investigate the influence of water vapor on the oxidation mechanisms. The Cu- and Al-containing alloys exhibited improved oxidation resistance over the Mn composition. For the Cu-containing alloy, a local attack of the Cu-rich phase was observed, which formed an Fe/Ni/Co/Cr spinel that was surrounded by Cr2O3. This oxide was thicker for the humid air atmosphere when compared to dry air, and the transition of the Cu oxide to the spinel was accelerated. The Al-containing HEA formed a thin Al2O3 scale with humidity suppressing AlN formation and forming a smoother oxide layer. The Al+Cu composition had the highest overall oxidation resistance (minimal local attack, no nitridation) and also showed a smooth oxide scale topography under humid air oxidation as opposed to a plate-like, rougher scale under dry air.

Microstructure evolution and strengthening mechanism of CoCrFeMnNi HEA/Zr-3 brazed joints reinforced by fine-grained BCC HEA and HCP Zr

In the pursuit of manufacturing intricate components for the nuclear industry, we developed a novel Zr63.2Cu36.8 (wt.%) alloy via vacuum melting for brazing applications involving equiatomic high-entropy alloys (HEA) of CoCrFeMnNi and zircaloy (Zr-3). We systematically investigated the influence of various brazing parameters on microstructure evolution and shear properties. Furthermore, we established a comprehensive understanding of the relationship between the lattice structure of interfacial products, residual stress, and fracture behavior in HEA/Zr-Cu/Zr-3 joints. Our findings revealed that under specific conditions (1010 °C for 10 min), the reaction products in HEA/Zr-Cu/Zr-3 joints consisted of lamellar HEAP/lamellar Zr(Cr,Mn)2, granular (Zr,Cu)/Zr2(Cu,Ni,Co,Fe), bulk Zr(Cr,Mn)2, and Zrss. With increasing temperature and prolonged holding time, the layered HEAP and Zr(Cr,Mn)2 phases adjacent to the HEA substrates thickened, while the relative amounts of Zr2(Cu,Ni,Co,Fe) decreased, with a remarkable increase in ductile Zrss. Growth kinetics analysis of the reaction layer and EBSD analysis indicated that the HEAP phases exhibited a lower growth rate compared to the Zr(Cr,Mn)2 layer during brazing, and both phases exhibited random grain orientations. Particularly noteworthy was the precipitation of (Zr,Cu) within the layered Zr(Cr,Mn)2, which increased and coarsened with higher temperatures and extended durations. Finite element analysis and TEM analysis revealed higher residual stresses at the non-coherent Zr(Cr,Mn)2/HEAP interface with a lattice mismatch of 40.6%. The body-centered cubic (BCC) structural HEAP, composed of fine grains, effectively mitigated the concentrated residual stresses due to its superior plasticity. Moreover, micro-nanoscale close-packed hexagonal (HCP) precipitates (Zr,Cu) were distributed within the brittle Zr(Cr,Mn)2 phases, contributing to the overall strength improvement of the joints. Consequently, high-quality HEA/Zr-3 joints were achieved, featuring a maximum strength of 172.1 MPa, equivalent to approximately 62.6% of the yield strength of Zr-3. These results highlight the potential of Zr63.2Cu36.8 (wt.%) alloys in advanced brazing applications.

High-throughput machine learning - Kinetic Monte Carlo framework for diffusion studies in Equiatomic and Non-equiatomic FeNiCrCoCu high-entropy alloys

Sluggish diffusion is postulated as an underlying mechanism for many unique properties in high-entropy alloys (HEAs). However, its existence remains a subject of debate. Due to the challenges of exploring the vast composition space, to date most experimental and computational diffusion studies have been limited to equiatomic HEA compositions. To develop a high-throughput approach to study sluggish diffusion in a wide range of non-equiatomic compositions, this work presents an innovative artificial neural network (ANN) based machine learning model that can predict the vacancy migration barriers for arbitrary local atomic configurations in a model FeNiCrCoCu HEA system. Remarkably, the model utilizes the training data exclusively from the equiatomic HEA while it can accurately predict barriers in non-equiatomic HEAs as well as in the quaternary, ternary, and binary sub-systems. The ANN model is implemented as an on-the-fly barrier calculator for kinetic Monte Carlo (KMC) simulations, achieving diffusivities nearly identical to the independent molecular dynamics (MD) simulations but with far higher efficiency. The high-throughput ANN-KMC method is then used to study the diffusion behavior in 1,500 non-equiatomic HEA compositions. It is found that although the sluggish diffusion is not evident in the equiatomic HEA, it does exist in many non-equiatomic compositions. The compositions, complex potential energy landscapes (PEL), and percolation effect of the fastest diffuser (Cu) in these sluggish compositions are analyzed, which could provide valuable insights for the experimental HEA designs.

Formation of Chemical Short-Range Order in Equiatomic CoNiCrFeMn High-Entropy Alloy. Atomistic MD/MC Simulation

Abstract—The formation of short-range order in the equiatomic high-entropy alloy (HEA) CoNiCrFeMn during annealing at moderate temperatures was studied using atomistic MD/MC simulation, including the exchange of atoms in the Monte Carlo (MC) scheme and the relaxation of its positions by the molecular dynamics (MD) method. It has been found that two types of chemical short range order (CSRO) regions are formed during annealing. One of them consist mainly of Fe and Co atoms, while others are enriched by Cr with Ni and Mn atoms at their boundaries. It is shown that the formation of short-range order includes several stages, the sequence of which is determined by the value of Cr–Cr, Fe–Co and Ni–Mn interatomic interactions.

Dual-interstitials promoted multiple mechanisms enhance strength-ductility synergy of an equiatomic high-entropy alloy

Although minor additions of interstitials have been employed to enhance the yield strength of high-entropy alloys (HEAs) with multi-principal elements, the significant loss of ductility occurs as the cost. In this work, to further improve strength-ductility synergy of the model face-centered cubic (FCC) CoCrFeMnNi HEA, dual-interstitial alloying of C and N is manipulated with the emphasis on tuning the microstructures and multiple strengthening mechanisms. C (0.6 at%) and N (0.8 at%) are completely dissolved in the FCC matrix after annealing at or above 1150 °C. The dissolution of the dual-interstitials in the matrix refines grains by impeding grain boundary migration via solute atmospheres. Nanoprecipitates including M23C6, Cr3C2 and Cr2(N, C) are dispersed in the recrystallized FCC matrix of the dual-interstitial HEAs upon annealing at 950–1000 °C. The Zener pinning pressure induced by these nanoprecipitates retards grain boundary migration and hence reduces grain sizes. The primary deformation mechanism is dislocation slip in both dual-interstitial HEAs with and without precipitates at the early deformation stages (e.g., 40% local strain), the mechanical twinning occurs at the medium and late deformation stages (e.g., 60% and 90% local strains, respectively) contributing to the high ductility of the HEAs. The synergetic strengthening effects of nanoprecipitates, grain boundaries, interstitial and substitutional solid-solution brings about high yield strength of 772 MPa and ultimate tensile strength of 1178 MPa at a large elongation of 34% in the dual-interstitial HEA containing carbides/carbonitrides nanoprecipitates. The contributions of the multiple mechanisms are quantified and discussed.

Thermochemical Analysis of Hydrogenation of Pd-Containing Composite Based on TiZrVNbTa High-Entropy Alloy

The microcalorimetric hydrogen titration technique combined with conventional volumetric measurements has been used to reveal peculiarities of the hydrogenation of the single-phase TiZrVNbTa equiatomic high-entropy alloy. The alloy has been produced in the form of microfibers by the pendent drop melt extraction technique. Palladium coating of the fibers has been applied to enable first hydrogenation at room temperature without additional activation. An analysis of the obtained data allows us to evaluate the dependence of hydrogenation enthalpy on the hydrogen concentration in the alloy. Three concentration ranges, presumably related to the formation of the hydrogen solid solution, monohydride and dihydride phases, have been identified, and the corresponding ΔH values of about −100, −80 and −60 kJ/mol H2, respectively, have been determined.

Microstructural, Mechanical, and Electrochemical Characterization of CrMoNbTiZr High-Entropy Alloy for Biomedical Application.

High-entropy alloys (HEA) with superior biocompatibility, high pitting resistance, minimal debris accumulation, and reduced release of metallic ions into surrounding tissues are potential replacements for traditional metallic bio-implants. A novel equiatomic HEA based on biocompatible metals, CrMoNbTiZr, was consolidated by spark plasma sintering (SPS). The relative sintered density of the alloy was about 97% of the theoretical density, indicating the suitability of the SPS technique to produce relatively dense material. The microstructure of the sintered HEA consisted of a BCC matrix and Laves phase, corresponding to the prediction of the thermodynamic CALPHAD simulation. The HEA exhibited a global Vickers microhardness of 531.5 ± 99.7 HV, while the individual BCC and Laves phases had hardness values of 364.6 ± 99.4 and 641.8 ± 63.0 HV, respectively. Its ultimate compressive and compressive yield strengths were 1235.7 ± 42.8 MPa and 1110.8 ± 78.6 MPa, respectively. The elasticity modulus of 34.9 ± 2.9 GPa of the HEA alloy was well within the range of cortical bone and significantly lower than the values reported for commonly used biomaterials made from Ti-based and Cr-Co-based alloys. In addition, the alloy exhibited good resistance to bio-corrosion in PBS and Hanks solutions. The CrMoNbTiZr HEA exhibited an average COF of 0.43 ± 0.06, characterized mainly by abrasive and adhesive wear mechanisms. The CrMoNbTiZr alloy's mechanical, bio-corrosion, and wear resistance properties developed in this study showed a good propensity for application as a biomaterial.

Високоентропійний NiFeCrWMo сплав, отриманий в процесі механічного легування

In this work, the evolution of the structure and phase composition of the multicomponent Ni-Fe-Cr-W-Mo system during mechanical alloying (MA) of an equiatomic mixture of elemental metal powders in a planetary mill is investigated. The formation of the phase composition and structure of the powdered equiatomic high-entropy NiFeCrWMo alloy at different stages of mechanical alloying was determined by scanning electron microscopy, X-ray diffraction and X-ray spectral analysis. It was found that during 10 hours of МА, a single-phase high-entropy alloy with the structure of a BCC solid solution in the nanostructural state with a crystallite size of 22 nm and a lattice strain (microstress) of 0.61 % was formed. It was shown that the metal components were completely dissolved in the solid state during mechanical alloying, in contrast to their limited solubility under equilibrium conditions. Moreover, despite the different features of the formation of solid solutions in high-entropy alloys and traditional materials, the order of dissolution of element atoms in the lattice of a solid solution follows general principles and occurs depending on the melting point in the following sequence: Ni→Fe→Cr→Mo→W. The average particle size of the produced powdered NiFeCrWMo high-entropy alloy is 3.8 μm, and their shape is predominantly spherical or close to spherical. The microstructure of the particles of the powdered NiFeCrWMo high-entropy alloy at the early stage (1.5 hours) of mechanical alloying is a layered structure formed in the process of grinding, deformation, and cold welding of particles of elemental metal powders. After 10 hours of МА, the microstructure of the alloy particles becomes homogeneous and contains a small amount of WC inclusions as a result of milling due to wear of grinding bodies in the MА process. The obtained NiFeCrWMo high-entropy alloy can be used in the future as a component/binder for other composite materials, for example, hard alloys based on WC to replace Co. Keywords: high-entropy alloy, mechanical alloying, structure, phase composition, solid solution, nanostructure

Mechanical Spectroscopy Study of CrNiCoFeMn High-Entropy Alloys.

The equiatomic high-entropy alloy of composition of CrNiCoFeMn with an FCC crystal structure was prepared by either induction melting or additive manufacturing with a selective laser melting (SLM) process, starting from mechanically alloyed powders. The as-produced samples of both kinds were cold worked, and in some cases re-crystallized. Unlike induction melting, there is a second phase, which is made of fine nitride and Cr-rich σ phase precipitates, in the as-produced SLM alloy. Young's modulus and damping measurements, as a function of temperature in the 300-800 K range, were performed on the specimens that were cold-worked and/or re-crystallized. Young's modulus values of (140 ± 10) GPa and (90 ± 10) GPa were measured from the resonance frequency of free-clamped bar-shaped samples at 300 K for the induction-melted and SLM samples, respectively. The room temperature values increased to (160 ± 10) GPa and (170 ± 10) GPa for the re-crystallized samples. The damping measurements showed two peaks, which were attributed to dislocation bending and grain-boundary sliding. The peaks were superposed on an increasing temperature background.

Development and characterization of a novel high entropy alloy strengthened through concurrent spinodal decomposition and precipitation

Strengthening mechanisms, which are commonly exploited by conventional alloys, can be effectively incorporated in high entropy alloys (HEAs) to improve their mechanical behaviour. In this light, compositional modification of equiatomic HEAs can be pursued in order to obtain specific microstructural features. Herein, a face centred cubic CoCuFeMnNi alloy was modified by the addition of a proper amount of Ti; a dedicated thermal treatment allowed to concurrently activate two different phase formation mechanisms, i.e. precipitation and spinodal decomposition. This resulted in a nanostructured microstructure, characterized by the presence of periodic modulations of Cu content and by nanosized coherent L12 Ni3Ti precipitates. Such microstructure resulted in a more than 100 % increase of yield strength after ageing treatment and allowed to retain a satisfactory ductility. Advanced microstructural characterization, coupled with the application of semi-empirical models allowed to understand the role of each microstructural feature in determining the alloy’s mechanical strength.