Mixture Of Solid Solution Research Articles

Phase prediction of high-entropy alloys based on machine learning and an improved information fusion approach

The phase design of high entropy alloys (HEAs) is an important issue since the phase structure affects the comprehensive properties of HEAs. Accurate prediction of phase classification can accelerate material design. In this paper, a new phase prediction framework is proposed using machine learning (ML) and an improved information fusion approach based on the Dempster-Shafer (DS) evidence theory. Considering that the classification results of different ML algorithms may conflict, and the traditional DS evidence theory cannot solve the problem of high conflict, we propose an improved information fusion approach based on the DS evidence theory. The basic probability assignment function is constructed using the ML algorithms. 761 HEAs samples are collected consisting of amorphous phase (AM), solid solution (SS), intermetallic compound (IM), and a mixture of SS and IM (SS + IM). For the small dataset of HEAs, we use a conditional generative adversarial network (CGAN) for data augmentation. Based on the enhanced dataset, the ML model is optimized by sparrow search algorithm (SSA), which can accelerate searching speed of model hyperparameters and improve the performance of the model. The results show that the proposed information fusion method performs better than several other existing techniques on the test set, and the prediction accuracy reaches 94.78 %. Meanwhile, the prediction accuracy of the proposed method is higher than that of the existing technology (93.17 %). It is proved that the proposed method can solve the high conflict problem effectively. Moreover, we present the interpretability analysis of the features by the Shapley additive explanations (SHAP) and the sensitivity matrix. A smaller atomic size difference δ (<6.6 %) is conducive to the formation of SS phase, while a larger δ (>6.6 %) is conducive to the formation of AM phase. A smaller enthalpy of mixing ΔHmix tends to form AM phase. In binary and ternary alloy systems, IM phase can be extracted by the mixing enthalpy ΔSmix < 10. In addition, we find that mean bulk modulus (K) and standard deviation of melting temperature (σT) are critical features to distinguish between SS and SS + IM.

Stabilizing Cr3+ in a mixture of solid solution phases for high-temperature applications

The major drawback of Cr-containing materials is the generation of toxic Cr6+ compounds, especially at high temperatures in contact with oxygen, alkali or alkaline earth elements/oxides/salts. In this work, we compared the oxidation of two different Cr3+ species, (a) Cr2O3 and (b) a solid-solution mixture of Ca(Al,Cr)12O19 and (Al,Cr)2O3, upon reheating (500–1500 °C) in the presence of CaO, Al2O3, and SiO2 under air atmosphere. The mixture of Ca(Al,Cr)12O19 and (Al,Cr)2O3 was found to be more stable (7.5 mg/kg Cr6+) than Cr2O3 (5646 mg/kg Cr6+). Prolonged reheating (up to 24 h) of Cr3+ solid-solution phases at 900 °C reveals a slight increase in Cr6+ (3.0 to 4.8 mg/kg and 7.5 to 9.1 mg/kg for sample M2 and M2-S (with SiO2), respectively). However, the Cr3+ solid-solution phases in the presence of SiO2 reveal higher Cr-evaporation than undoped counterparts. Nonetheless, the mixture of (Al,Cr)2O3 and Ca(Al,Cr)12O19 hardly showed reoxidation and was more inert.

Study of the structural and magnetic properties at high temperature of Ni-Co-Mn-Al Heusler alloy prepared by an unconventional route

ABSTRACT Ni, Co, Mn, and Al elemental powders have been ball milled in a planetary mill for various periods, up to 32 h. The obtained powder was characterized with XRD, SEM-EDS, DSC, high-temperature-XRD, and VSM techniques to study morphology, composition, thermal transitions, structural and magnetic changes occurring at high temperatures. At the end of the milling process, a particle mixture consisting of agglomerated grains with a rounded shape and an average size of about 60 µm was formed. XRD patterns of the as-milled powders revealed the presence of a nanocrystalline solid solution mixture with (L10) and (B2) structures. HT-In-situ XRD characterizations confirmed the complete formation of the B2 ordered structure from 573 K. The austenitic Heusler phase B2 remains stable during one hour of isothermal holding and its proportions increase between 648 and 773 K. Under the heating effect, crystallites size grows up greatly with increasing holding temperature, nevertheless the micro-strains decrease sharply from 0.98% at room temperature to 0.31% at 773 K. Magnetic features of the milled alloy enhance further during the heating process, making it magnetically soft with the most intriguing values of Ms, Mr, and Hc between 648 and 773 K. This is owing to the complete development of the homogeneous and ordered Heusler B2 phase and the significant increase in crystallite size with the relaxation of residual stresses resulting from the direct effects of temperature.

Graded Inconel 625 coatings with in-situ processing of Ni3Al

Ni superalloys have been widely used to process coatings due to a bouquet of attractive properties in a wide range of temperature. However, higher performance Ni alloys are typically those that offer larger processing challenges. Materials systems have been studied to mitigate this challenge. In hardfacing coatings multilayers have been processed both to reduce the detrimental effects of dilution with the substrate and to enhance the resistance to crack propagation, the latter of particularly relevance when depositing alloys reinforced with hard particles with a reduced weldability but that offer enhanced performance at the surface. The present study addressed the effects of customizing a commercial Inconel 625 atomized alloy, with increasing additions of Ni and Al elemental powder mixtures, to obtain multilayered coatings with a composition and property gradient. The gradual additions of Ni + Al powder mixture to the IN 625 atomized alloy allow for the in-situ synthesis of aluminides while maintaining good weldability, increasing mechanical properties and oxidation resistance. Results show a continuous solidification microstructure, crack-free multilayer coatings with smooth chemical composition profiles and property gradient. A gradual change on the strengthening mechanisms is identified, from solid solution on the first layer of IN 625 to a mixture of solid solution and Ni3Al precipitate dispersion on the top layer processed with the feedstock richer in the Ni + Al powder mixture. These changes induced increasing elastic modulus, hardness and oxidation resistance at 1300 °C following the chemical composition gradient in coatings.

Tungsten combustion in impact initiated W–Al composite based on W(Al) super-saturated solid solution

Element W can effectively improve the density of energetic structural materials. However, W is an inert element and does not combust in air. To change the reaction characteristics of W, 60 at.% Al was introduced into W through mechanical alloying. XRD analysis shows that after 50 h of ball milling, the diffraction peak of Al completely disappears and W(Al60) super-saturated solid solution powder is obtained. Further observation by HAADF and HRTEM reveals that the W(Al60) super-saturated solid solution powder is a mixture of solid solution and amorphous phase. Based on the good thermal stability of W(Al60) alloy powder below 1000 °C, W(Al60)–Al composite was synthesized by hot pressing process. Impact initiation experiments suggest that the W(Al60)–Al composite has excellent reaction characteristics, and multiple types of tungsten oxides are detected in the reaction products, showing that the modified W is combustible in air. Due to the combustion of tungsten, the energy release rate of the W(Al60)–Al composite at speed of 1362 m/s reaches 2.71 kJ/g.

Derivation of unit cell volume, and lattice parameter of cubic high entropy alloys from volume size factors

An equation has been derived to predict unit cell volume of high entropy alloys, HEA's, by two different methods. In the first method, a HEA is considered as a mixture of solid solutions. Based on an equation previously reported to calculate unit cell volume of intermetallic compounds, an expression to calculate unit cell volume of HEA's was obtained. In the second method, a HEA is modeled as a mixture of solute element atoms surrounded by different environments. Using the effective volume of solute atoms in these environments, the unit cell volume of a HEA was derived. Both treatments led to the same equation. For cubic HEA's lattice parameters were calculated. The predicted lattice parameters were compared with those reported for 79 HEA's. Lattice parameters were also calculated using the equivalent of Vegard's law for these alloys. Average errors were 0.64%, and 0.53% when Vegard's law, and the equation derived in this work were used, respectively. Although these average errors seem acceptable, they were as high as 4.27%, and 4.70% when Vegard's law, and the equation proposed are applied, respectively. The roles on error, of method to determine chemical composition, method to measure lattice parameter, and type of elements present on the alloy were examined.

Machine learning approach to predict new multiphase high entropy alloys

High entropy alloys with multi-principal elements have interested the research community due to the promising properties and tunable microstructure. In the current study, the multiphase alloy system with a mixture of solid solution and intermetallic (SS+IM) was predicted using a machine learning approach with a data set of 636 alloys. The Algorithms used are Logistic Regression, Decision Tree, Support Vector Machine (SVM) classifier, Random Forest, Gradient Boosting Classifier, and Artificial Neural Network (ANN). ANN has shown the best accuracy of more than 80% for the test data. The new alloys were prepared and characterized to verify the prediction and it is found that ANN is having more accurate prediction in the studied alloy system. Statistical analysis of the established data set reveals an overlapping boundary between the design parameters that hinders the successful prediction. Experimental data confirms the formation of new multiphase alloys.

Controlling lattice oxygen activity of oxygen carrier materials by design: a review and perspective

The lattice oxygen activity of oxygen carriers is critical to chemical looping processes and can be effectively controlled with prepared (i) solid solution mixtures, (ii) ternary oxide phases or (iii) core–shell structured oxygen carriers.

The Structural and Thermodynamic Analysis of Phase Formation Processes in Equiatomic AlCoCuFeNiCr High-Entropy Alloys

Phase formation processes in equiatomic AlCoCuFeNiCr high-entropy alloys have been studied by means of x-ray diffraction method, microstructure analysis and microhardness measurements. Thermodynamic and structural criteria for predicting the phase composition of the alloys were considered. It is shown that in AlCoCuFe, AlCoCuFeNi and AlCoCuFeNiCr alloys the two-phase mixture of solid solutions on the base of the BCC and FCC lattices is formed. With a decrease in the fraction of Al atoms, the tendency to disordering of BCC solid solution occurs. It was also established that alloys under investigation reveal a dendritic structure in which Cu-enriched FCC phase is deposited in the regions between the dendrites of the main BCC phase. The correlation between microhardness of the alloys and volume fractions of phase constituents and their thermodynamic characteristics are revealed.

Machine learning reveals the importance of the formation enthalpy and atom-size difference in forming phases of high entropy alloys

Despite outstanding and unique properties, the structure-property relationship of high entropy alloys (HEAs) is not well established. The machine learning (ML) is used to scrutinize the effect of nine physical quantities on four phases. The nine parameters include formation enthalpies determined by the extended Miedema theory, and mixing entropy. They are highly related to the phase formation, common ML methods cannot distinguish accurately. In this paper, feature selection and feature variable transformation based on Kernel Principal Component Analysis (KPCA) are proposed, the feature variables are optimized, the distinction of phases is carried out by Support vector machine (SVM) model. The results indicate that elastic energy and atom-size difference contribute significantly in the formation of different phases. The accuracy of testing set predicted by SVM based on four feature variables and KPCA (4V-KPCA) is 0.9743. The F1-scores predicted detailedly by SVM based on 4V-KPCA for the considered alloy phases are 0.9787, 0.9463, 0.9863 and 0.8103, corresponding to solid solution, amorphous, the mixture of solid solution and intermetallic, and intermetallic respectively. The extended Miedema theory provides accurate thermodynamic properties for the design of HEAs, and ML methods (especially SVM combined KPCA) are powerful in the prediction of alloy phases.

SYNTHESIS AND ELECTRICAL CONDUCTIVITY OF SOLID SOLUTIONS OF THE SYSTEM RbF-PbF2-SnF2

In the system RbF–PbF2–SnF2 are formed solid solutions of the heterovalent substitution RbxPb0,86‑xSn1,14F4-x (0 &lt; x ≤ 0,2) with structure of β–PbSnF4. At x &gt; 0,2 on the X-ray diffractograms, in addition to the basic structure, additional peaks are recorded that do not correspond to the reflexes of the individual fluorides and can indicate the formation of a mixture of solid solutions of different composition. For single-phase solid solutions, the calculated parameters of the crystal lattice are satisfactorily described by the Vegard rule. The introduction of ions of Rb+ into the initial structure leads to an increase in the parameter a of the elementary cell from 5.967 for x = 0 to 5.970 for x = 0.20. The replacement of a part of leads ions to rubium ions an increase in electrical conductivity compared with β–PbSnF4 and Pb0.86Sn1.14F4. Insignificant substitution (up to 3.0 mol%) of ions Pb2+ at Rb+ at T&lt;500 K per order of magnitude reduces the conductivity of the samples obtained, while the nature of its temperature dependence is similar to the temperature dependence of the conductivity of the sample β-PbSnF4. By replacing 5 mol. % of ions with Pb2+ on Rb+, the fluoride ion conductivity at T&gt; 450 K is higher than the conductivity of the initial sample Pb0,86Sn1,14F4 and at temperatures below 450 K by an order of magnitude smaller. With further increase in the content of RbF the electrical conductivity of the samples increases throughout the temperature range, reaching the maximum values at x≥0.15 (σ573 = 0.34–0.41 S/cm, Ea = 0.16 eV and σ373 = (5.34–8.16)•10-2 S/cm, Ea = 0.48–0.51 eV, respectively). In the general case, the replacement of a part of the ions of Pb2+ with Rb+ to an increase in the electrical conductivity of the samples throughout the temperature range. The activation energy of conductivity with an increase in the content of RbF in the low-temperature region in the general case increases, and at temperatures above 400 K is inversely proportional decreasing. The nature of the dependence of the activation energy on the concentration of the heterovalent substituent and its value indicate that the conductivity of the samples obtained increases with an increase in the vacancies of fluoride ions in the structure of the solid solutions.

The elastic-strain energy criterion of phase formation for complex concentrated alloys

An empirical method is developed, based on the calculated theoretical elastic-strain energy, to predict the phase formation and its stability for complex concentrated alloys. The method prediction quality is compared with the traditional empirical rules based on the atomic-size mismatch, enthalpy of mixing, and valence-electron concentration for a database of 235 alloys. The “elastic-strain energy vs. valence-electron concentration” criterion shows an improved ability to distinguish between single-phase solid solutions, and mixtures of solid solutions and intermetallic phases when compared to the available empirical rules used to date. The criterion is especially strong for alloys that precipitate the µ phase. The theoretical elastic-strain-energy parameter can be combined with other known parameters, such as those noted above, to establish new criteria which can help predict the design of novel complex concentrated alloys with the on-demand combination of mechanical properties.

The Elastic-Strain Energy Stability Criterion for Complex Concentrated Alloys

An empirical method is developed, based on the calculated theoretical energy, to predict the phase formation and its stability for complex concentrated alloys. The method prediction quality is compared with the traditional empirical rules based on atomic-size mismatch, enthalpy of mixing and valence electron for a database of 235 different alloys. Considering the different available empirical methods used to date, the elastic-strain energy vs. valence electron concentration criterion shows an improved ability to distinguish between single-phase solid solutions, mixtures of solid solutions and intermetallic phases. The criterion is especially strong for alloys that precipitate the µ phase. The theoretical elastic-strain-energy parameter can be combined with other known parameters, such as those noted above, to establish new criteria which can help predicting the design of novel high-entropy alloys with on-demand combination of mechanical properties.

Interaction of Structural Components of Titanium Composite in Vacuum at 1150°C

The interaction of a Ti + 10 Mo titanium alloy, which serves as a matrix in a tribological material, with calcium fluoride CaF2 and boron nitride BN, which play the role of a solid lubricant, during their heating and sintering in a vacuum of 10–3 Pa at 1150°C for 15 and 120 min, respectively, has been studied. In the heating of a Ti + 10 Mo + CaF2 model sample for 15 min and sintering of Ti + 10 Mo + CaF2 CAM1 for 120 min, calcium fluoride does not interact with the Ti + 10 Mo matrix and does not change its composition and structure; a transition layer between the matrix and solid lubricant does not form. Thus, calcium fluoride preserves its initial lubricating properties. In the sintering of Ti + 10 Mo + 13 CaF2 CAM1 for 120 min, a composite antifriction material with a microheterogeneous structure is synthesized. Its structure is a mixture of solid solutions of molybdenum in α- and β-titanium, which has a body-centered cubic lattice and face-centered hexagonal lattice, in which calcium fluoride CaF2 is distributed in the form of inclusions. In the heating of a Ti + 10 Mo + BN model sample for 15 min and sintering of Ti + 10 Mo + BN CAM2 for 120 min, the interaction of the Ti+10Mo alloy with boron nitride BN occurs to form a transition layer with the phase composition α-TiMo + TiB + TiN + BN. In the sintering of Ti + 10 Mo + BN CAM2 for 120 min, a composite material with a microheterogeneous structure is synthesized. Its structure is a solid solution of Mo in α-Ti with a face-centered hexagonal lattice, strengthened by products of interaction of titanium with nitrogen and boron, TiN and TiB, in which boron nitride BN is distributed in the form of inclusions.

Influence of remelting on microstructure, hardness and corrosion behaviour of AlCoCrFeNiTi high entropy alloy

High entropy alloys are a newly developed class of alloys, which tend to form a single solid solution or a mixture of solid solutions with simple crystal structures. These alloys possess excellent mechanical properties, thermal stability and corrosion resistance. In the present paper, an AlCoCrFeNiTi high entropy alloy was obtained by induction melting, and the influence of the remelting process on the mechanical and corrosion resistance characteristics of the alloy was investigated. Thus, optical and scanning electron microscopy revealed less phase segregation and a fine dendritic structure for the remelted alloy, while corrosion tests indicated that present alloy, in remelted state, has better corrosion resistance than as cast alloy and stainless steel. The Vickers microhardness measurements demonstrated an improvement of the alloy microhardness by remelting process due to the decrease in phase segregation and the increase in dendrite refinement level.

The Influence of Electron Beam Oscillation on the Crystallization and Structure of Dissimilar Steel-Bronze Welds

The paper contains the findings of the metallographic study of dissimilar metal welds (steel 12Х21Н5Т and bronze BrХ-06) made by electron-beam welding (EBW) with beam modulation (transversal and X-shaped oscillation with triple beam splitting). The research shows that beam oscillation causes the metals to stir in the weld pool. As a result, welds have a very heterogeneous structure by width. X-shaped oscillation causes more intensive stirring than transversal oscillation. This leads to more homogenous stirring of crystallizing phases in the centre of the weld. The heterogeneous structure caused by beam oscillation gives the weld a very heterogeneous solidity both by width and depth. Triple beam splitting heated from bronze promotes the homogenous weld structure which is a fine-dispersed mechanical mixture of two systems: a eutectic based on copper and a mixture of solid solutions based on [alpha]-Fe and [gamma]-Fe. Such a structure makes the weld equalizes the solidity of the weld both by width and depth.

Structure and magnetoresistance of a Ni79.7Fe14.0Co2.8Zr2.0Cu1.5 thin film

The structure and magnetoresistance R of thin films based on Ni80Fe20 permalloy doped with Co, Zr, and Cu have been examined by X-ray diffraction analysis and resistance measurement. The films have been obtained by ion plasma sputtering on oxidized silicon, fused quartz, and glass ceramic cold substrates. It has been shown that the structure of a film in the initial state is a mixture of solid solutions based on two phases: Ni(fcc) particles with a size of L ≈ 8 nm and (Zr0.67Ni0.22O0.11)γ particles with a size of L ≈ 12 nm. The R(H) dependences on the strength and direction of the magnetic field H have been obtained at room temperature for film samples in the initial state and after isothermal annealing at 653 K for 1 h. According to R(H) dependences and X-ray diffraction analysis, films in the initial state are assumingly in a superparamagnetic state, whereas they exhibit ferromagnetic properties after isothermal annealing.

가스분무성형 Cu-5Ni-10Sn 합금의 미세조직 및 시효강화

In this study, Cu-5Ni-10Sn(wt%) spinodal alloy was manufactured by gas atomization spray forming, and the microstructural features and mechanical properties of Cu-5Ni-10Sn alloy have been investigated during homogenization, cold working and age-hardening. The spray formed Cu-5Ni-10Sn alloy consisted of an equiaxed microstructure with a mixture of solid solution <TEX>${\alpha}$</TEX>-(CuNiSn) grains and lamellar-structure grains. Homogenization at <TEX>$800^{\circ}C$</TEX> and subsequent rapid quenching formed a uniform solid solution <TEX>${\alpha}$</TEX>-(CuNiSn) phase. Direct aging at <TEX>$350^{\circ}C$</TEX> from the homogenized Cu-5Ni-10Sn alloy promoted the precipitation of finely distributed <TEX>${\gamma}$</TEX>' or <TEX>${\gamma}-(Cu,Ni)_3Sn$</TEX> phase throughout the matrix, resulting in a significant increase in microhardness and tensile strength. Cold working prior to aging was effective in strengthening Cu-5Ni-10Sn alloy, which gave rise to a maximum tensile strength of 1165 MPa. Subsequent aging treatment slightly reduced the tensile strength to 1000-1100 MPa due to annealing effects.

Zn2(CuIn)1−S2 photocatalysts synthesis by a hydrothermal process using H4EDTA as complexing agent

Abstract The study of the Zn 2 x (CuIn) 1− x S 2 (0 ≤ x ≤ 1) solid solutions formation by hydrothermal synthesis using ethylenediaminetetraacetic acid (H 4 EDTA) as a complexant and surfactant agent is reported for the first time. Different synthesis parameters were varied: the H 4 EDTA concentration, the initial pH value, the Tu concentration, the duration and temperature of autoclaving process. The as obtained powders were characterized by X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and UV/vis/NIR diffuse reflection spectroscopy (DRS). The XRD and EDX results show that, with a careful adjustment of the reaction conditions, especially of the H 4 EDTA concentration and initial pH value of the precursor solution, a mixture of solid solutions with sphalerite type structure can be obtained, which transforms into a single phase solid solution after heat treatment. The particles, as revealed by SEM investigations, have nanoporous hexagonal microplates morphology, about 1 μm thick and several microns in diameter. The Cu 0.159 In 0.111 Zn 1.778 S 2 photocatalyst obtained by this method presents photocatalytic activity for hydrogen evolution from aqueous solutions containing S 2− ions as sacrificial agent, even without cocatalyst.

A study of the dependence of the mass transfer on the structural factors of the electrodes in electrospark alloying with Ni-Cr-Al alloys

The dependence of the mass transfer parameters on the structure of the Ni-Cr-Al and Ni-Cr-NiAl electrode systems in the electrospark alloying of steel 45 is studied. The phase composition of the cast, sintered, and hot-pressed alloys is a mixture of solid solutions based on nickel, chromium, and NiAl intermetallide. The mass-transfer coefficient in the case of alloying with cast and hot-pressed alloys is 2 to 3.5 times higher than that in the event of alloying with sintered alloys. This difference is due to the different structures of the electrodes prepared by different techniques.