Ni-Al System Research Articles

Vacuum synthesis of composite powder of Al–Ni system for fabricating aluminum-matrix composite reinforced with Al3Ni particles

Vacuum synthesis of composite powder of Al–Ni system for fabricating aluminum-matrix composite reinforced with Al3Ni particles

The impact of small Zr addition to Al–Ni cast alloy for elevated temperature applications

Most aluminium casting alloys are based on the eutectic system Al–Si, which has weak thermal properties. Alloys from the eutectic Al–Ni system on the other hand have higher thermal stability and good casting properties and are therefore promising for casting applications. Using casting simulations, a copper mold was designed to achieve cooling rates above 100 K/s with the aim of producing a Zr-rich supersaturated solid solution. Microstructural analysis revealed that the addition of Zr leads to notable changes in the microstructure characterised by the formation of primary Al3Zr and αAl dendrites. Subsequent heat treatment revealed that Zr-enriched alloys undergo significant age hardening, which showed an improvement in microhardness due to effective Al3Zr precipitation.

Determination of γ/γ' interface free energy for solid state precipitation in Ni-Al alloys from molecular dynamics simulation.

Interface free energy is a fundamental material parameter needed to predict the nucleation and growth of new phases. The high cost of experimentally determining this parameter makes it an ideal target for calculation through a physically informed simulation. Direct determination of interface free energy has many challenges, especially for solid-solid transformations. Indirect determination of the interface free energy from the nucleation data has been done in the case of solidification. However, a slow on molecular dynamics (MD) simulation time scale atomic diffusion makes this method not applicable to the case of nucleation from the solid phase when precipitate composition is different from that in matrix. To address this challenge, we outline the development of a new technique for determining the critical nucleus size from an MD simulation using a recently developed method to accelerate solid-state diffusion. The accuracy of our approach for the Ni-Al system for Ni3Al (γ') precipitates in a Ni-Al (γ) matrix is demonstrated well within experimental accuracy and greatly improves upon previous computational methods [Herrnring et al., Acta Mater. 215(8), 117053 (2021)].

Composition design and crystallization behavior of Zr–Cu–Ni–Al bulk metallic glasses

The Zr–Cu–Ni–Al system was explored in this study, and seven new compositions of Zr-based bulk metallic glasses (BMGs) were designed by combining different proportions of binary eutectic phases Zr38Cu62, Zr76Ni24 and Zr51Al49, and rod-like shape samples were prepared with different diameters using the copper mold casting method. Modifying the proportion coefficient of these eutectic units, the width of the supercooled liquid region was increased from 79 to 95 K, and the thermal stability of the prepared metallic glass was improved. Differential scanning calorimetry was used to investigate the non-isothermal and isothermal crystallization behavior of the prepared samples. Noticeably, there was a small low-temperature exothermic peak before the glass transition temperature Tg in the non-isothermal crystallization process, which was related to the structural relaxation. The crystallization transition activation energy fitted by the Kissinger equation had the same variation trend as that obtained by the Arrhenius equation. Among the four metallic glasses studied, the glassy phase of Zr55·5Cu23·25Ni9Al12.25 was more stable, showing higher glass transition activation energy and longer incubation time. In addition, the isothermal crystallization processes of four metallic glasses were studied according to the Johnson-Mehl-Avrami (JMA) model. The calculated average Avrami exponents were >2.5, indicating that the nucleation rate increased during the isothermal crystallization process.

Sputter deposition of ZnO–AlN pseudo-binary amorphous alloys with tunable band gaps in the deep ultraviolet region

ZnO–AlN pseudo-binary amorphous alloys (a-ZAON hereinafter) with tunable band gaps in the deep ultraviolet (DUV) region have been synthesized using magnetron sputtering. The miscibility gap between ZnO and AlN has been overcome using room-temperature sputtering deposition, leveraging the rapid quenching abilities of sputtered particles to fabricate metastable but single-phase alloys. X-ray diffraction patterns and optical transmittance spectra revealed that the synthesized films with chemical composition ratios of [Zn]/([Zn] + [Al]) = 0.24–0.79 likely manifested as single-phase of a-ZAON films. Despite their amorphous structures, these films presented direct band gaps of 3.4–5.8 eV and thus high optical absorption coefficients (105 cm−1). Notably, the observed values adhered to Vegard’s law for crystalline ZnO–AlN systems, implying that the a-ZAON films were solid solution alloys with atomic-level mixing. Furthermore, atomic force microscopy analyses revealed smooth film surfaces with root-mean-square roughness of 0.8–0.9 nm. Overall, the wide-ranging band gap tunability, high absorption coefficients, amorphous structures, surface smoothness, and low synthesis temperatures of a-ZAON films position them as promising materials for use in DUV optoelectronic devices and power devices fabricated using large-scale glass and flexible substrates.

Phase Relations of the Sm–Ni–Al Ternary System at 800 °C in the 30–100 at.% Al Region

The Sm–Ni–Al phase relationships at 800 °C have been investigated by using several well–focused experimental techniques such as X–Ray Powder Diffraction (XRPD), Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Microprobe Analysis (EPMA). The isothermal section of the Sm–Ni–Al system at 800 °C was constructed according to the present experimental results. More than 50 alloys have been synthesized and characterized in the 30–100 at.% Al region. At 800 °C, 9 intermetallic phases have been confirmed, characterized and their relationships have been established. In the Al-rich corner, the presence of two ternary invariant reactions have been postulated whilst along the 16.67 at.% Sm isopleth, the presence of two structurally related extended solid solutions have been observed. The determined phase equilibria at 800 °C are discussed and compared with the isothermal section at 500 °C already reported in literature.

Development and investigation of a porous metal-ceramic substrate for solid oxide fuel cells

The process of creating a porous metal-ceramic material based on Ni-Al alloy and gadolinium-doped cerium oxide (CGO) using the thermal explosion method has been investigated. This study aims to analyze the effect of CGO on the thermal explosion parameters and the architecture of the resulting Ni-Al-CGO materials. In this regard, the influence of adding CGO powder to the Ni-Al system on the synthesis process and structure formation during controlled heat loss thermal explosion has been studied. Dependencies of temperature and time characteristics of the thermal explosion on initial parameters have been measured. It has been demonstrated that the concentration of CGO in the initial mixture and heat dissipation from the sample significantly affect the rate of the exothermic reaction. The phase composition of the obtained porous materials, depending on the CGO content and the temperature of subsequent vacuum annealing, was analyzed using X-ray diffraction. The chemical composition and microstructure of the synthesis products were examined through electron microscopy and energy-dispersive X-ray spectroscopy. The possibility of forming metal-ceramic composites with a porosity of 60–65 % for use as supporting substrates for solid oxide fuel cells with a NiO/CGO anode has been shown. An anodic layer of NiO/CGO was applied to a metal-ceramic base of the composition (Ni+25 %Al)+5 %CGO using screen printing, which was then annealed in an air atmosphere at 1300 °C and reduced at 900 °C in a hydrogen atmosphere. The dilatometric method determined that adding 40 wt.% Cr to a mixture of Ni-Al powders reduces the average coefficient of thermal expansion of the new material.

Thermodynamic Analysis of Al-Ni, Al-Cu Alloys System Using Calphad Method

Abstract: The CALPHAD technique, in conjunction with the PBIN database, is employed to conduct a thorough thermodynamic analysis and assessment of the binary alloy systems Al-Cu and Al-Ni. This study explores the thermodynamic properties, including phase diagrams, Gibbs free energies, and thermodynamic molar activities across the entire compositional range. The temperature maintained for assessment is 2000-2050 K. The doping characteristic of the AL-Ni binary system is more epitaxial and useful for doping industries. The correspondence of Raoult’s law is more precise in the Al-Ni binary alloy system due to its better doping characteristics. The entropy and the enthalpy of both systems increase. The greater decrease in the Gibbs curve and activity predicted the more stability of the alloying system Al-Ni. Within the Al-Ni system, a composition range of 0.4-0.6 mole percent at a temperature of 2050 K is identified as the most stable, contrasting with the Al-Cu system, which exhibits the least stability. The lattice vibrations mode and Brillion zone growth during alloying contribute to highly epitaxial characteristics, with pure and sharp attractive interactions among alloying elements. Negative deviation from ideality in activity is observed in the Al-Ni system, further supporting its increased stability. This is attributed to the lower Gibbs energy and higher enthalpy accordance. Both Al-Cu and Al-Ni binary systems show the highest level of equilibrium and stability. The enthalpy values of both alloying systems gradually increase with temperature. In the solid era of both binary alloy systems, Al-Cu and Al-Ni, the ferrite phase is identified as the stable phase. The most stable ferrite phase, capable of withstanding the highest temperatures, holds promise for applications in industrial sectors and materials metallurgy. Keywords: Thermodynamic properties, CALPHAD method, Thermo-calc simulation package, Alloys.

Phase equilibria, thermodynamic assessment, and the mechanical property of B2 phase of the Al-Ga-Ni ternary system

Ni-based alloys, known for their exceptional mechanical properties and high corrosion resistance in harsh environments, are extensively utilized in gas-turbine engines for propulsion and energy generation. Of particular interests are the L12-Ni3Al and B2-NiAl phases in Al-Ni alloy, which can be the strengthening phases for superalloy and high temperature structural materials, respectively. After Ga addition in the Al-Ni system, these promising intermetallic compounds form a continuous compositional range encompassing the L12-Ni3(Al, Ga) and B2-Ni(Al, Ga) phases. They exhibited distinct mechanical properties contingent on the ratio of Al to Ga. Additionally, Ni and Al are the commonly used substrates in the electronic package and Ga has been used as a filler material for interconnection. Hence, the Al-Ga-Ni phase equilibria are of practical importance for designing L12-Ni3(Al, Ga) and/or B2-Ni(Al, Ga) phase-dispersed Ni-based alloys as well as for evaluating interfacial reactions in the Al/Ga/Ni contacts. However, the Al-Ga-Ni ternary system remains relatively unexplored. In this study, Al-Ga-Ni isothermal sections at 600 (Ni-lean), 900, and 1000 (Ni-rich) °C were experimentally constructed based on equilibrated alloys. Additionally, a CALPHAD-type thermodynamic assessment for the Al-Ga-Ni ternary system was comprehensively performed based on all available experimental information. Furthermore, the Young's modulus and hardness of four B2-Al(Ga, Ni) compounds were determined, revealing that the addition of Ga to B2-NiAl phase would lead to a significant decrease in Young's modulus but a notable enhancement in hardness.

Development of an interatomic potential for L12 precipitates in Fe–Ni–Al alloys

Fe–Ni-based alloys have been considered as candidate structural materials for advanced nuclear reactors, and some of their excellent properties are particularly associated with L12 precipitates dispersed in the alloys. For a better understanding of the irradiation response, classical molecular dynamics is an essential tool to simulate the irradiation-induced defect formation and subsequent microstructural evolution. We here develop an interatomic potential for L12(Ni,Fe)3Al precipitates in the ternary Fe–Ni–Al system. The fitting parameters are tuned to describe the lattice and elastic constants of NiFe solid solutions and defect formation/vacancy migration energies in the fcc matrix. Furthermore, the lattice properties and defect energies of L12(Ni,Fe)3Al are considered for the fitting. We demonstrate the developed potential reproduces the lattice and defect properties with reasonable accuracy by comparison with density functional theory calculations, existing empirical potentials, and experimental data. This potential will be useful to investigate the defect formation and evolution of (Ni,Fe)3Al precipitates in the alloys under irradiation, which would provide critical insights into the materials design strategy to achieve enhanced properties.

Theoretically evaluating transition metal activated two-dimensional bilayer tetragonal AlN nanosheet for high-performance HER/OER/ORR electrocatalysts

The search for catalysts with high activity in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) processes has been an eminent avenue for mankind to acquire clean and renewable energy. To this end, more than a dozen transition metal (TM)-doped AlN systems have been investigated based on first-principles calculations in this study. Our calculation results show that Co@AlN-VAl can be operated as OER/ORR bifunctional catalysts with ηOER/ηORR of 0.5/0.33 V. Meanwhile, Pd@AlN-VAl exhibits the most excellent catalytic activity due to the very low HER overpotential (ηHER=0.009V). Furthermore, the origin of the high activity for Co@AlN-VAl in the OER/ORR process is illustrated by stating the d-band center and descriptor (φ). The Bader charge, the crystal orbital Hamiltonian population (COHP), spin density, and density of states (DOS) are analyzed to further recognize the intrinsic characteristics of this system. The study provides theoretical guidance for the application of AlN system in electrocatalysis and a window for new SACs.

Thermodynamics and kinetics of interdiffusion in Ni//NiAl diffusion couples

The growth behavior of Ni3Al after nucleation at the Ni/NiAl interface was investigated by using macroscopic diffusion couples at low annealing temperatures of 973–1073 K. The thickness and grain size of the Ni3Al phase at different annealing temperatures were statistically analyzed by scanning electron microscopy to evaluate the growth kinetics of the Ni3Al layer. According to the growth rate exponent, the growth of Ni3Al layer to NiAl is almost completely controlled by volume diffusion (VD) when it is above 1023 K, and by boundary diffusion (BD) when it is below 1023 K. In contrast, the growth of Ni3Al into Ni is controlled by VD almost whether at 1023 K or 1073 K. Remarkably, a continuous Al-rich Ni grain layer was formed at the Ni3Al/Ni interface by diffusion-induced recrystallization (DIR), and the experimental results for DIR region of composition and growth behavior were numerically analyzed using the thermodynamic and kinetic models, respectively. The analyses suggest that the composition of the DIR region in the Ni(Al) binary system can be determined by the thermodynamic conditions of the chemical driving force model (CDF model). Additionally, kinetic analysis using the new extended model (NE model) indicates that under current annealing conditions, interface reaction and BD control growth at the moving boundary of the DIR region. Furthermore, the temperature stability range of Ni5Al3 in the Ni//NiAl system was subjected to systematic analysis.

Microstructure and mechanical properties of highly dense Si3N4 ceramics with ZrN–AlN–Re2O3 (Re=Yb, Y, Nd, Ce, La) additives

The Si3N4 ceramics with ternary ZrN–AlN–Re2O3 (Re=Yb, Y, Nd, Ce, La) and ZrN–AlN system as sintering additives were prepared by hot-pressed sintering with vacuum environment at 1750°C-30min–30MPa. Subsequently, the effect of the ternary additives system with 2 wt% Re2O3 on phase transformation, grain boundary phases, microstructure, and mechanical properties of the Si3N4 ceramics were investigated firstly. All samples achieved the high β-Si3N4 phases transformation (≥98.86%), while the grain boundary phases RexZr1-xO(4-x)/2 and Yb2Si2O7 were detected in the sintered Si3N4 ceramics with Re2O3 additives. Additionally, compared with Si3N4 ceramic not contain Re2O3 additives, the Si3N4 ceramics added Re2O3 additives presented the textured microstructure with more elongated rodlike β-Si3N4 grains based on the XRD and SEM results. Consequently, the sample S-Ce with added CeO2 additive shows the highest relative density of 99.85% and optimal fracture toughness of 8.75 ± 0.36 MPa m1/2. The sample S–Nd with added Nd2O3 additive presented a highest bending strength of 1061.78 ± 41.76 MPa. Sample S–Yb with added Yb2O3 additive presented the maximum Vickers hardness of 16.35 ± 0.07 GPa. The results of this study can provide a helpful reference for the preparation of high-performance Si3N4 ceramics.

Erratum to: Phase Formation in the V2O5–AlN System

Erratum to: Phase Formation in the V2O5–AlN System

Express-diagnostics of the properties of ЫРЫ materials using chrono-topographic analysis of thermal vision data

Subject of research: the article is devoted to the development of a methodology for express diagnostics of material properties based on the measurement of macrokinetic parameters of the SHS process.
 Purpose of research: plotting the dependence of the microhardness of SHS products on the propagation velocity of the SHS wave and its temperature.
 Methods and objects of research: the research objects were the SHS process in the Ni-Al system and the reaction products; To measure the propagation velocity of a high-temperature synthesis wave, an original method of chrono-topographic analysis of thermal imaging data was used; temperature control was carried out by an original method of spectral-brightness pyrometry. The study of the microhardness of experimental samples was carried out using an FM-800 microhardness tester.
 Main results of research: in the course of experimental studies, it was shown that the error in determining the propagation velocity of the SHS wave by the method of chrono-topographic analysis of thermal imaging data is 0.1 %, and the error in temperature measurement by the method of spectral-brightness pyrometry is estimated at 0.5 %. It is concluded that the main factor influencing the total error in the SHS wave propagation velocity in the experiment is the inaccuracy of setting the charge parameters for a set of samples. The absolute value of the total error was 3.2 %. A diagnostic trajectory has been constructed that makes it possible, based on the SHS propagation rate and reaction temperature, to evaluate the microhardness of the product and draw a conclusion about the quality of charge preparation for the production of a material with desired properties.

Obtaining of Metal-Matrix Alloys Based on Ni-Al for ESD Coatings Formation

The experimental results of obtaining complex-alloyed intermetallic alloys by the method of liquid-phase self-propagating high-temperature synthesis (SHS) and their subsequent use for the formation of wear-resistant coatings by the method of electrospark deposition (ESD) are submitted. Metal oxides Cr2O3, NiO, CoO and mineral concentrate containing a larger part of ZrO2 in its composition were used as a melt charge for the SHS experiments. Alloys based on Ni-Al system dopped with Cr, Zr, Co, and C were obtained. It was established that extra addition of C led to the refinement of the alloys microstructure (3-5 times). ESD coatings were formed on steel 45 using the obtained alloys as anode material. The coatings formed by using the alloys doped by Co, Zr, Cr and extra addition of C (0.4 wt%) proved to be maximum wear resistant.

Exothermic Reactions in AlNi Foils Produced by Rolling Powders

The possibility of manufacturing multilayer reaction foils of the Al-Ni system by rolling a powder mixture is considered. The sequence and temperatures of phase transformations during heating was established by the differential thermal analysis and X-ray phase analysis. The formation of the intermetallic compounds in the foils fabricated via rolling just mixed powder occurs only when a liquid phase appears (660°C). However, the foils fabricated from mechanically activated powders exhibit significant exothermic effect at temperature of 320°C unnecessarily for a liquid phase formation and can be proposed as a multilayer reactional foils for local heating in the technology of joining of various materials.

Welding in Ti–Al and Ni–Al Systems by Self-Propagating High-Temperature Synthesis

Welding in Ti–Al and Ni–Al Systems by Self-Propagating High-Temperature Synthesis

Structural composition of electrospark coatings obtained by Ni—Al alloys on steels

Coatings were obtained by electrospark deposition using anode materials based on the Ni-Al system. According to the research results it is most expedient to use two alloys based on Ni3Al and NiAl with an additional content of the Ni5Al3 phase for the coatings formation. The microstructure of the resulting coatings consists of columnar crystallites, in which the concentration of the anode components (Ni, Al) increases, and the content of the cathode component (Fe) decreases along the height of the coating from the surface to the base. It has been established that the content of Fe in crystallites in different areas of the coating changes most significantly.

Формирование интерметаллического покрытия Ni-=SUB=-3-=/SUB=-Al холодным газодинамическим напылением механически обработанной в планетарной мельнице порошковой смеси Ni-Al

The features of the formation of an intermetallic Ni3Al coating by cold spraying of a Ni–Al powder mixture mechanically treatment in a planetary mill and prepared in a V-shaped mixer are presented. It is shown that the powder deposition efficiency is 1.5 times higher when coatings are obtained from a mechanically treated powder mixture of Ni and Al components. Subsequent high-temperature treatment in the furnace chamber creates a condition for the formation of an intermetallic compound of the Ni-Al system of various stoichiometric proportions.