Non-equiatomic High Entropy Alloy Research Articles

Effect of element N on microstructure and tribological properties of CoCrFeNiV alloy at severe temperature

In this study, CoCrFeNiV non-equiatomic high entropy alloys (HEAs) with varying N content were prepared using vacuum hot-press sintering. The effects of N content on the alloy's microstructure, mechanical properties, and tribological behavior at different temperatures were investigated. The results indicate that the N-added alloys primarily maintain an FCC phase. With increasing N content, the σ phase in the alloy gradually decreases, while the VN content increases, leading to grain refinement. This results in a 10.7 % increase in hardness, a 9 % increase in compression strength, and a 56 % increase in compression deformation. Below 400 °C, the primary wear mechanisms are adhesive wear, spalling wear, and slight oxidative wear, while above 600 °C, oxidative wear dominates. The addition of N reduced the wear rates of the alloy by 33.8 %, 8.1 %, and 31.3 % at RT, 200 °C, and 600 °C, respectively, and decreases the coefficient of friction at all temperatures. In summary, N addition improves the alloy's tribological performance at various temperatures.

Dynamic response of equiatomic and non-equiatomic CrMnFeCoNi high-entropy alloys under plate impact

A typical Fe-rich non-equiatomic CrMnFeCoNi high-entropy alloy (HEA), Cr10Mn10Fe60Co10Ni10, and the equiatomic Cr20Mn20Fe20Co20Ni20 HEA, are investigated via plate impact experiments along with in situ free surface velocity measurements. Both the initial and postmortem samples are characterized with transmission electron microscopy and electron backscatter diffraction. These two HEAs contain a single face-centered cubic phase, are texture-free, and have similar grain sizes. Dynamic yield stress and spall strength of the non-equiatomic CrMnFeCoNi are lower by ∼55 % and 15 % than those of its equiatomic counterpart, respectively. After shock compression, dislocation slips, stacking faults, Lomer-Cottrell locks and nanotwins are found in the postmortem samples of both HEAs. Due to the reduced stacking fault energy in the non-equiatomic HEA, more deformation twins and newly formed hexagonal close-packed phases are found. For spallation, intergranular voids are larger in size but smaller in quantity than intragranular voids for both HEAs. Both intragranular or intergranular voids show strong dependence on grain boundary misorientation.

Grain growth kinetics, phase evolution during annealing and strain rate sensitivity of TRIP-assisted, dual-phase, non-equiatomic high entropy alloy

Transformation-induced plasticity-assisted dual-phase high-entropy alloys (TRIP-DP-HEAs) belong to a recently developed class of HEAs. TRIP-DP-HEAs have been reported to exhibit superior strength-ductility combination at room temperature as well as at high temperatures. Small amounts of carbon additions to TRIP-DP-HEAs are known to further improve the strength as a result of interstitial solid solution and nanoprecipitate strengthening effects. Current investigation compares the grain growth kinetics in a metastable, dual-phase (FCC and HCP), Fe49.5Mn30Co10Cr10C0.5, carbon-containing high entropy alloy (C-DP-HEA) with that in the corresponding carbon-free variant, Fe50Mn30Co10Cr10 HEA (DP-HEA). The alloys after being subjected to cold rolling, were annealed at 900 °C, 1000 °C and 1100 °C for 3, 30, 60 and 120 min, followed by water quenching. Slower grain growth kinetics was observed in C-DP-HEA due to Zener pinning by carbide particles. The activation energy for grain growth in C-DP-HEA was determined to be 339.71 kJ/mol, which is larger than that of DP-HEA (282.68 kJ/mol). The microstructures of the C-DP-HEA samples, after annealing at 900 °C for different durations of times and quenching, were investigated. The HCP phase fraction in the microstructure initially decreased with increase in annealing time/grain size and later increased with further increase in annealing time/grain size. This is explained based on the counteracting effect of grain boundary density and back stresses acting in samples having increased grain size. Strain rate sensitivity (SRS) parameter, ‘m’, was evaluated for both C-DP-HEA and DP-HEA. The strain rate jump tests were conducted at two quasi-static strain rates, 1 × 10−3 s−1 and 5 × 10−3 s−1, and at room temperature as well as at higher temperatures, 900 °C, 1000 °C and 1100 °C. The ‘m’ value was found to depend on the grain size, test temperature, and the presence of carbon in the alloy.

A strong and ductile biocompatible Ti40Zr25Nb25Ta5Mo5 high entropy alloy

A non-equiatomic high entropy alloy (HEA) Ti40Nb25Zr25Ta5Mo5 (at.%) was designed by replacing 5% Ta with 5% Mo in a precursor Ti40Nb25Zr25Ta10 HEA for improved mechanical properties and reduced density. The Ti40Nb25Zr25Ta5Mo5 HEA fabricated by copper mould casting exhibited a nearly equiaxed grain structure (grain size: 96 ± 16 μm), but within each equiaxed grain, dendritic structures are discernible in the backscattered electron imaging mode. These dendrites are enriched in Ta, Nb and Mo, while the inter-dendritic regions contain higher Zr and Ti. The as-cast HEA achieved tensile yield strength (σ0.2) of 976 ± 8 MPa and strain to fracture (εf) of 16.80 ± 1.86%, well above the minimum requirements of σ0.2 and εf for medical-grade titanium alloy Ti–6Al–4V (759 MPa and 10%). The formation of microscale and nanoscale shear bands and the presence of significant dislocations in the shear band boundary region played a key role in allowing this as-cast HEA to achieve the excellent combination of tensile strength and ductility. Furthermore, the HEA exhibited a lower wear rate, lower coefficient of friction and much higher corrosion resistance in Hank's solution (electrochemical assessments) than Ti–6Al–4V, making it a promising alternative biomedical alloy.

Solidification and tribological behaviors of CoCrFeNiSi0.5-(Al,Ti) non-equiatomic high entropy alloy coatings fabricated by direct laser deposition

In order to evaluate the difference in the effects of Al and Ti elements on the microstructure and tribological behaviors of CoCrFeNi-based high entropy alloy (HEA) coatings, CoCrFeNiSi0.5-(Al,Ti) non-equiatomic HEAs coatings were prepared using direct laser deposition (DLD). The phase constitution, solidification microstructure and tribological behaviors of the HEA coatings were investigated. The results indicated that CoCrFeNiSi0.5 HEA coating was composed of face centered cubic (FCC) phase with microstructure of columnar and cellular grains. The addition of Al and Ti led to a columnar-to-equiaxed transition (CET) in the HEA coatings. When only Al was added (CoCrFeNiSi0.5Al0.5), the primary phase transformed into a body centered cubic (BCC) phase (94 vol%). Additionally, Cr3Si formed in the interdendrite (ID) region, and a spinodal decomposition structure emerged in the dendrite (DR) region. Conversely, with the inclusion of Ti alone (CoCrFeNiSi0.5Ti0.5), the matrix maintained its FCC phase, but Ni16Ti6Si7 (G phase, 20.9 vol%) and Cr15Co9Si6 (15.1 vol%) were generated in the ID and DR regions, respectively. Incorporating both Al and Ti (CoCrFeNiSi0.5Al0.5Ti0.5) significantly reduced the G phase content in the ID region to 7.9 vol% and led to the formation of dispersed Fe3Al nanoparticles with an average size of 99 nm in the DR region. The CoCrFeNiSi0.5 HEA coating exhibited the lowest hardness (249 HV0.1), the highest friction coefficient (0.778), and the poorest wear resistance. For the HEA coatings containing Al and Ti, the microhardness significantly increased to over 700 HV0.1, and the friction coefficient decreased to around 0.6. However, the wear resistance of the CoCrFeNiSi0.5Al0.5 HEA coating was almost equivalent to that of the CoCrFeNiSi0.5 with a wear loss of 5.1 mg. By contrast, the HEA coatings containing Ti demonstrated notably improved wear resistance, with wear losses of only 2.2 mg and 2.4 mg for the CoCrFeNiSi0.5Ti0.5 and CoCrFeNiSi0.5Al0.5Ti0.5 HEA coatings, respectively.

Effect of annealing treatments on microstructure and mechanical properties of high-entropy alloy Cr10 Mn10Fe60Co10Ni10

A face-centered cubic (FCC) non-equiatomic high-entropy alloy (HEA), Cr10Mn10Fe60Co10Ni10, is processed via cold-rolling and subsequent annealing at 800−1200 °C with different cooling methods. All the annealing treatments lead to fully recrystallized microstructures with various grain sizes and precipitate types. The mechanical properties under uniaxial tension are obtained along with microstructure characterizations of postmortem samples. The sample annealed at 800 °C followed by furnace cooling yields a reasonable combination of high strength and good ductility. The yield strength and ultimate tensile strength are 43% and 19% higher than those of the sample annealed at 800 °C followed by water quenching, with only a uniform elongation ∼6% reduction. The yield strength variations of all the annealed samples are explained with a structure-based strength model. After fracture, all the samples show strong 〈111〉 texture along the tensile direction. Besides dislocation slip, deformation twinning and multiple phase transitions contribute to high strength and effective work hardening as additional deformation mechanisms. The newly formed hexagonal close-packed and body-centered cubic phases follow the Shoji–Nishiyama and Kurdjumov–Sachs orientation relations with the FCC matrix, respectively. Given the “treatment method−microstructure−mechanical property” relationship in this study, combining the advantages of the steel and HEAs, this kind of Fe-rich HEA bears great potentials to serve under practical conditions.

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.

Low-Temperature Elastic Properties of Molybdenum Doped Non-Equiatomic High Entropy Alloys of the Fe-Co-Ni-Cr System

The mechanical properties and microstructural evolution of a medium-entropy alloy Co17.5Cr12.5Fe55Ni10Mo5 (at%) in a low temperature range (including the record low temperatures region down to 0.5 K) were investigated. It has been established that low-temperature plastic deformation initiates martensitic phase transformations in this alloy, and the values of the dynamic modulus of elasticity correlate with the degree of phase transformations.

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.

Co50Cr20Ni20Fe5Mn5 high entropy alloy: Overcoming the strength-ductility trade-off of Cantor alloy

In this study, we aimed to design and investigate a non-equiatomic high strength and ductile high entropy alloy (HEA) by controlling the FCC phase stability. A new Co-rich Co50Cr20Ni20Fe5Mn5 HEA was synthesized by vacuum arc remelting and processed through homogenization, cold rolling, and recrystallization. The alloy’s phase composition, mechanical properties, and plastic deformation behavior were characterized using X-ray diffraction (XRD), tensile testing, and Transmission Electron Microscopy (TEM) analysis. The tensile properties of the alloy were compared with those of the conventional Co20Cr20Ni20Fe20Mn20 HEA produced and processed using the same technique and route. The results showed that reducing the Fe and Mn concentrations while increasing the Co concentration reduced the FCC phase’s stability, leading to the occurrence of partial FCC to HCP phase transformation upon cooling from high temperature and TWIP-TRIP effects during tensile deformation. The Co50Cr20Ni20Fe5Mn5 HEA exhibited improved mechanical properties, including higher yield strength (502 MPa), ultimate tensile strength (1002 MPa), and total elongation (50%) compared to the reference Cantor HEA (405 MPa, 766 MPa, and 40%, respectively). The principal strengthening mechanisms contributing to the increased yield strength with higher Co concentration were identified as initial HCP phase strengthening and grain boundary strengthening. The enhancement in ultimate tensile strength and ductility is attributed to the TWIP-TRIP effects during the tensile deformation of the Co50Cr20Ni20Fe5Mn5 HEA.

Chemical Composition Optimization of Biocompatible Non-Equiatomic High-Entropy Alloys Using Machine Learning and First-Principles Calculations

Obtaining a suitable chemical composition for high-entropy alloys (HEAs) with superior mechanical properties and good biocompatibility is still a formidable challenge through conventional trial-and-error methods. Here, based on a large amount of experimental data, a machine learning technique may be used to establish the relationship between the composition and the mechanical properties of the biocompatible HEAs. Subsequently, first-principles calculations are performed to verify the accuracy of the prediction results from the machine learning model. The predicted Young’s modulus and yield strength of HEAs performed very well in the previous experiments. In addition, the effect on the mechanical properties of alloying an element is investigated in the selected Ti-Zr-Hf-Nb-Ta HEA with the high crystal symmetry. Finally, the Ti8-Zr20-Hf16-Nb35-Ta21 HEA predicted by the machine learning model exhibits a good combination of biocompatibility and mechanical performance, attributed to a significant electron flow and charge recombination. This work reveals the importance of these strategies, combined with machine learning and first-principles calculations, on the development of advanced biocompatible HEAs.

Microstructure evolution and erosion behaviour of thermally sprayed AlCoCrNiMo0.1 high entropy alloy coating

Novel AlCoCrNiMox (x = 0.1 wt%) non-equiatomic high entropy alloy (HEA) powders were synthesized by mechanical alloying. A single solid-solution was formed. X-Ray Diffraction (XRD) analysis of milled powders reveals a BCC phase after 20 h of milling. Field emission scanning electron microscopy (FESEM) with EDAX mapping confirmed the formation of a homogenous mixture. The milled alloy was coated onto a 316 steel substrate using High-velocity Oxy-fuel (HVOF) coating. The slurry erosion resistance exhibited by the coating was tested using Water-jet Erosion tester with 24 m/s to 30 m/s jet velocity at 30°, 45°, 60°, and 90° angular impingement. Spallation due to adhesion with subsequent layered lamellae fracture was observed to occur during erosion.

A novel and sustainable method to develop non-equiatomic CoCrFeNiMox high entropy alloys via spark plasma sintering using commercial commodity powders and evaluation of its mechanical behaviour

A novel approach to developing high entropy alloys (HEAs) using spark plasma sintering (SPS) was explored in this work where a mix of commercial commodity powders like Ni625, CoCrF75, and 316L was used instead of pre-alloyed powders avoiding the expensive pre-alloying steps like mechanical alloying or gas atomizing. Three non-equiatomic HEAs, based on Co, Cr, Fe, Ni, and Mo were designed and developed by blending the powders which were sintered via SPS and resulted in a single FCC phase after homogenization. The HEAs were microstructurally and mechanically characterized with tensile and hot compression tests up to a temperature of 750 °C showing excellent properties. The maximum room temperature tensile strength and ductility demonstrated was 712 MPa and 62% respectively, by the alloy Co23.28Cr28.57Fe25.03Ni21.01Mo2.1. Moreover, the same alloy exhibited a compression strength greater than 640 MPa with a ductility above 45% at a temperature of 750 °C. Also, this study paves the way for a novel fabrication route that offers more flexibility to develop new HEAs cost-effectively and efficiently which is crucial for the discovery of new materials over high-throughput techniques. Using such commodity alloys also opens the possibility of developing ingot casting from recycled scraps avoiding the direct use of critical metals.

Evaluation of Equiatomic CrMnFeCoNiCu System and Subsequent Derivation of a Non-Equiatomic MnFeCoNiCu Alloy.

Investigation into non-equiatomic high-entropy alloys has grown in recent years due to questions about the role of entropy stabilization in forming single-phase solid solutions. Non-equiatomic alloys have been shown to retain the outstanding mechanical properties exhibited by their equiatomic counterparts and even improve electrical, thermal, and magnetic properties, albeit with relaxed composition bounds. However, much remains to understand the processing-structure-property relationships in all classes of so-called high-entropy alloys (HEAs). Here, we are motivated by the natural phenomena of crystal growth and equilibrium conditions to introduce a method of HEA development where controlled processing conditions determine the most probable and stable composition. This is demonstrated by cooling an equiatomic CrMnFeCoNiCu alloy from the melt steadily over 3 days (cooling rate ~4 °C/h). The result is an alloy containing large Cr-rich precipitates and an almost Cr-free matrix exhibiting compositions within the MnFeCoNiCu system (with trace amounts of Cr). From this juncture, it is argued that the most stable composition is within the CrMnFeCoNiCu system rather than the CrMnFeCoNi system. With further optimization and evaluation, a unique non-equiatomic alloy, Mn17Fe21Co24Ni24Cu14, is derived. The alloy solidifies and recrystallizes into a single-phase face-centered cubic (FCC) polycrystal. In addition to possible applications where Invar is currently utilized, this alloy can be used in fundamental studies that contrast its behavior with its equiatomic counterpart and shed light on the development of HEAs.

Powder Metallurgy Processing and Characterization of the χ Phase Containing Multicomponent Al-Cr-Fe-Mn-Mo Alloy

High entropy alloys present many promising properties, such as high hardness or thermal stability, and can be candidates for many applications. Powder metallurgy techniques enable the production of bulk alloys with fine microstructures. This study aimed to investigate powder metallurgy preparation, i.e., mechanical alloying and sintering, non-equiatomic high entropy alloy from the Al-Cr-Fe-Mn-Mo system. The structural and microstructural investigations were performed on powders and the bulk sample. The indentation was carried out on the bulk sample. The mechanically alloyed powder consists of two bcc phases, one of which is significantly predominant. The annealed powder and the sample sintered at 950 °C for 1 h consist of a predominantly bcc phase (71 ± 2 vol.%), an intermetallic χ phase (26 ± 2 vol.%), and a small volume fraction of multielement carbides—M6C and M23C6. The presence of carbides results from carbon contamination from the balls and vial during mechanical alloying and the graphite die during sintering. The density of the sintered sample is 6.71 g/cm3 (98.4% relative density). The alloy presents a very high hardness of 948 ± 34 HV1N and Young’s modulus of 245 ± 8 GPa. This study showed the possibility of preparing ultra-hard multicomponent material reinforced by the intermetallic χ phase. The research on this system presented new knowledge on phase formation in multicomponent systems. Moreover, strengthening the solid solution matrix via hard intermetallic phases could be interesting for many industrial applications.

A novel alloy design for non-equiatomic high-entropy alloy (Cr–Fe–Ni–Ti–Nb): predicting entropy mix and enthalpy mix

A novel alloy design for non-equiatomic high-entropy alloy (Cr–Fe–Ni–Ti–Nb): predicting entropy mix and enthalpy mix

Temperature-dependent yield stress of single crystals of non-equiatomic Cr-Mn-Fe-Co-Ni high-entropy alloys in the temperature range 10-1173 K

The temperature-dependent yield strengths of [1¯23]-oriented single crystals of four quinary non-equiatomic Cr-Mn-Fe-Co-Ni high-entropy alloys (HEAs) were investigated at temperatures of 10-1173 K. They exhibit similar trends with a rapid decrease of the critical resolved shear stress (CRSS) from 10 K to 300 K, followed by a much slower rate of decrease with increasing temperature and a plateau above 873 K. The HEAs with the highest and lowest Cr contents exhibit the highest and lowest yield strengths respectively at 10 K, but almost identical yield strengths at 300 K. Thus, at cryogenic temperatures, the magnitude of the temperature dependence of yield strength is positively correlated with Cr content. All the non-equiatomic HEAs also exhibit similar dislocation structures with planar arrays of smoothly-curved dislocations without any preferred orientations. Their stacking fault energy (SFE) decreases with increasing Cr content. An empirical expression is proposed to describe the composition dependence of SFE in the Cr-Mn-Fe-Co-Ni quinary system. A new route for optimizing the alloy design of non-equiatomic Cr-Mn-Fe-Co-Ni alloys in terms of strength and ductility through the combination of mean-square atomic displacement (MSAD) and SFE is discussed based on the results obtained.

Effects of aging treatment on microstructure and mechanical properties of non-equiatomic high entropy alloy

In this study, the cryogenically-processed FeCoNi1.5CuB0.5Y0.2 HEAs (high-entropy alloys) were subjected to aging treatment, such as different aging temperatures T (unaged sample, 700 °C, 750 °C, 800 °C), aging times t (unaged sample, 10 h, 12 h, 14 h) and the aging cycles N (unaged sample, one time, two times, three times). Under this condition, the changing laws of microstructure and mechanical properties of HEAs were explored. According to the experiment, with the increase of the aging temperature, the prolongation of the aging time or the growth of the number of aging cycles, the overall mechanical properties of the material have been significantly improved. In particular, when the aging conditions were T = 750 °C, t = 12 h, and N = 2 times, the grain size of the optimized sample was reduced, and a large number of finely dispersed precipitates appeared, which can produce excellent strong-plastic synergy. Further analysis revealed that the complex interacting multi-component in the HEA constitute the heterogeneity level of the microstructure and also lead to effective multi-component strengthening. Especially in the samples after optimized aging parameters (DCAT 7), the activated back stress at boundaries of grains and the synergistic effect of nanoparticles and twins contribute to high strain hardening. In terms of micromechanical characteristics, the modulus of elasticity and nanohardness of each phase were obviously enhanced. In terms of macroscopic mechanical properties, Vickers hardness, compressive strength and maximum compression ratio also reached their maximum values, which were 53.4%, 19.6% and 43.5% higher than those of the single cryogenic sample, separately. Obviously, the overall strength-ductility has been improved simultaneously.

Extraordinary creep resistance in a non-equiatomic high-entropy alloy from the optimum solid-solution strengthening and stress-assisted precipitation process

Improving creep resistance has commonly been achieved by the optimization of alloy design that results into strong solid-solution strengthening and/or coherent precipitates for dislocation blockage. High-entropy alloys (HEAs), despite their single-phase solid-solution nature, only exhibit creep properties that are comparable to precipitate-strengthened ferritic alloys. Moreover, many HEAs are found to be plagued with many incoherent second phases after long-term annealing, which reduces the lifetime and thus prohibits their usage at elevated temperatures. The present work demonstrates the extraordinary creep resistance of a non-equiatomic Al0.3CoCrFeNi HEA, in which the creep strain rate is found to be several orders of magnitude lower than the Cantor alloy and its subsets. Using a suite of characterization tools such as atom probe tomography (APT) and transmission electron microscopy (TEM), it was shown that a B2 precipitate phase that has been widely seen during annealing is suppressed during the early stage of the creep deformation. Currently, metastable and coherent L12 precipitates emerge and provide significant creep strengthening. This observation is rationalized by the coupling between the applied stress and the lattice mismatch. In the range of 973 ∼ 1033 K, the stress exponent and activation energy were determined to be 3–6.53 and 390–548.2 kJ·mol−1, respectively. The creep lifetime, on the other hand, is comparable to Cantor subset alloys because the precipitate free zone near the grain boundaries does not provide sufficient constraint for the grain boundary cavity growth. The present work provides a pathway to design novel HEAs with improved creep resistance.

Machine learning accelerated design of non-equiatomic refractory high entropy alloys based on first principles calculation

The properties of High Entropy Alloys (HEAs) strongly depend on the composition and content of elements. However, it was difficult to obtain the optimized element composition through the traditional "trial and error" method. The non-equiatomic HEAs have a large range for composition exploration by changing the content of elements, but the current research methods are difficult to analyze comprehensively. In this work, the prediction model with high accuracy is established by mixture design, the first principles calculation and machine learning. The model is used to predict the elastic properties and Poisson's ratio of non-equiatomic Mo–Nb–Ta–Ti–V HEAs, and the prediction results agree well with experimental data. The optimal element composition range of elastic properties and Poisson's ratio could be obtained. The influence of elements on the elastic properties and Poisson's ratio is analyzed through the calculation of features' importance. The results show that the content of Ti has the greatest contribution to the elastic properties and Poisson's ratio of the alloy. This model can not only obtain a large amount of data quickly and accurately but also help us to establish the relationship between element content and mechanical properties of non-equiatomic Mo–Nb–Ta–Ti–V RHEAs and provide theoretical guidance for experiments.