Fe-Al Alloys Research Articles

Influence of Cu Alloying on the Microstructure and Properties of the Al–Fe Alloy, Produced by Electromagnetic Casting and Subjected to Equal-Channel Angular Pressing

Influence of Cu Alloying on the Microstructure and Properties of the Al–Fe Alloy, Produced by Electromagnetic Casting and Subjected to Equal-Channel Angular Pressing

Enhancing magnetostriction in FeAl alloys via crystal growth orientation tuning by a trace amount of Pt doping

Iron-based cubic alloy systems opened the door to the development of magnetostrictive materials with moderate magnetostriction, low cost, and good mechanical properties. At the as-cast state, the grain growth orientation of these alloy systems is close to random, which deteriorates magnetostriction. Doping with certain elements can tune the growth orientation to enhance magnetostriction. However, the driving force for the crystal growth along preferential orientation is still not clear. Here in this work, revealed by density functional theory (DFT) calculation, Pt doping can tune the crystal growth direction of FeAl along <100> crystal direction (same as easy magnetization direction), which can be utilized to realize 90° domain-switching and thus magnetostriction is enhanced greatly. These are confirmed by experimental results. The magnetostriction increases from 29 ppm to 80 ppm, representing a 176% enhancement through doping with 0.4 at.% Pt. The maze magnetic domain structures, observed by magnetic force microscope, are also preferentially <100> oriented and feature stripes. In consideration of the similarity between this study and our previous study on FeGa alloy (C. Zhou et al., 2020), it can be expected that our methods can be extended to other magnetostrictive materials and help develop polycrystals with desired orientations.

Thermal conductivity of binary Al alloys with different alloying elements

This work investigates the physical properties of several binary Al-Si/Ni/Fe/Cu/Mg alloys with varying alloying element contents and microstructures. The findings indicate that as the content of alloying elements increases, the number of secondary phases in binary Al alloys rises, and these phases become coarser. In hypereutectic compositions, primary phases in Al-Ni and Al-Fe alloys take on a needle-like morphology with high aspect ratios, forming a dendritic network. Regarding properties, in the hypoeutectic region, both thermal conductivity and electrical conductivity of binary alloys initially decrease sharply, followed by a more gradual decline with the addition of alloying elements. This trend occurs because thermal conductivity is mainly influenced by supersaturated solid solutions. In hypereutectic Al-Ni and Al-Fe alloys, the presence of large, needle-like primary phases significantly hinder the heat transfer, resulting in a more apparent reduction in both thermal conductivity and electrical conductivity. Among the five binary alloys, Al-Ni and Al-Fe alloys, which have lower solute concentrations of alloying elements in the Al matrix, exhibit the highest thermal and electrical conductivity. Furthermore, with increasing alloying element contents, the phonon thermal conductivity of Al-Si alloy increases more markedly compared to other alloys. The study will offer a fundamental understanding for the development of advanced alloy.

Additive manufacturing of sustainable and heat-resistant Al-Fe-Mo-Si-Zr alloys

Improving the sustainability of metals and alloys is essential for slowing down global warming. The reason is that their extraction and production stand for about 40% of all greenhouse gas emissions in the industrial sector. This motivates new alloy design and processing criteria such as the (1) preferred use of abundant and sustainable alloying elements and (2) improved material tolerance against impurity intrusion from recycling. In this context, additive manufacturing (AM) is attractive, through rapid solidification, capable of quenching impurities into a solid solution state, avoiding formation of large intermetallics and introduction of metastable phases. Here, by using this approach we show how iron, an important scrap-related contaminant in aluminum alloys, can be turned from a harmful into a valuable ingredient. Specifically, the addition of Mo and Si facilitates the formation of beneficial metastable body-centred cubic (BCC) Al12(Fe, Mo)3Si phase, instead of more stable but detrimental intermetallic variants commonly observed in Al-Fe alloys. The as-built microstructures have excellent thermal stability, tested up to 200hours at 300 °C, because of low diffusivity of Fe and the formation of Zr shell. We find that for such supersaturated alloys, two issues are important, namely (a) the heterogeneous microstructures in the as-built condition, (b) the evolution of metastable precipitates during heating. We suggest that this type of approach help to guide sustainable alloy design via AM and other rapid solidification processes.

Study of Hot-Dip Aluminium Plating Based on Micro-Morphology and Coating Bond Strength

Hydrogen barrier coatings with Al2O3 as the main component are a good choice for solving the hydrogen embrittlement problem during hydrogen transportation in long-distance pipelines. However, the difference in the coefficients of thermal expansion between the substrate and the Al2O3 coating limits its further utilisation and development. In this study, rare earth oxides were added to the molten aluminium solution, and a Fe-Al transition layer was introduced on the surface of X80 steel by hot-dip plating to solve the thermal mismatch. Here, the microstructure and bonding strength of the hot-dip aluminium layer were investigated. It is found that the hot-dip aluminium coating consists of the outermost aluminium-rich layer and the inner Fe-Al alloy layer, and the microstructure of the two will change with the change in dip plating parameters. The best overall performance of the hot-dip aluminium layer was obtained from X80 steel substrate at a dip plating temperature of 700 °C and a dip plating time of 5 min. This coating has a good interface, moderate thickness, and a bond strength of 49 N. This study provides a reference value for solving the thermal mismatch between the steel substrate and the Al2O3 hydrogen barrier coating generated by subsequent anodising.

Anodic Dissolution of Al–Fe and Al-Fe-Si Alloys in Emimcl–AlCl3 Electrolyte

To produce over 99.9% of high-purity Al from Al–Fe alloy containing Al6Fe and Al–Fe–Si alloy containing β-AlFeSi by electrorefining, their anodic dissolution and cathodic electrodeposition characteristics were investigated in an EmImCl–AlCl3 ionic liquid electrolyte at 323 K. Constant potential electrolysis showed that Fe dissolved from Al–Fe anode at 0.7 V vs Al/Al(III) and from Al–Fe–Si anode at 1.4 V, and was co-deposited with Al on the cathode. Notably, anodic dissolution potential of Fe was changed by forming β-AlFeSi, and Si did not dissolve from β-AlFeSi at either potential. A combination of controlled anodic dissolution potential and the use of the Al alloy containing β-AlFeSi further suppressed the dissolution and cathodic co-deposition of Fe, affording high-purity Al on the cathode.

Experimental Measurements and Kinetic Investigation of Fe-Al Alloy Layer During the Galvanizing Process

Experimental Measurements and Kinetic Investigation of Fe-Al Alloy Layer During the Galvanizing Process

Evolution of surface oxide layers during isothermal oxidation of a multi-component oxide dispersion strengthened Fe3Al alloy

Evolution of surface oxide layers during isothermal oxidation of a multi-component oxide dispersion strengthened Fe3Al alloy

Load transfer behavior in semisolid formed hypereutectic Al-Fe-based alloys during tensile creep

The tensile creep behavior of semisolid formed hypereutectic Al-Fe-based alloys (for short Al-5Fe-based alloys) is investigated at temperatures ranging from 200 °C to 350 °C and stresses ranging from 30 MPa to 100 MPa. A power law model incorporating the “generalized” load transfer term is employed to rationalize creep data for Al-5Fe-based alloys with respect to that of the pure aluminum as a corresponding matrix without second phases and/or reinforcements. This expression proves more suitable for describing the creep characteristics of Al-5Fe-based alloys. The AlFe phases in the alloys transfer and bear load, and have no interaction with dislocations practically, which is the main reason for the creep strengthening of Al-5Fe-based alloys. The results obtained in this study are validated by creep data for Al-Fe alloys obtained by a thorough literature review.

Tailoring thermal conductivity and microstructure of Al–Fe alloys by addition of Sc2O3 and variable cooling rates

Al–Fe alloy is a kind of high thermal conductivity alloy, which are widely utilized in the communication and automobile industries. The thermal conductivity is greatly affected by the morphology, size, and distribution of iron-rich intermetallic phases (Fe-rich phases), pores, and Al grains. The evolution of microstructure and thermal conductivity of Al–Fe alloys by adding Sc2O3 particles and adjusting cooling rates are systematically studied by optical and scanning electron microscopy, and synchrotron X-ray imaging. The results show that Sc2O3 addition reduces the size and increases the number of primary Fe-rich phases, while increasing the grain size of Al matrix. The Sc2O3 promote their nucleation of primary Fe-rich phases and partial Sc solutes inhibit their growth, resulting in the improvement of thermal conductivity and mechanical properties. The remaining Sc2O3 particles have large lattice misfit with Al, led to the formation of coarsen size Al. The highest thermal conductivity is 214 W/(m·K) in the alloy with Sc2O3 and slow cooling rate. Sc2O3 addition increase the thermal conductivity of the studied alloys, i.e., an increment of 3 W/(m K) (by 1.1 %) at slow cooling rate by and an increment of 11 W/(m K) (by 6.2 %) at fast cooling rate. This study provides a new strategy to improving thermal conductivity of Al alloy for both academia and industry.

Enhanced oxygen evolution reaction using carbon-encapsulated Co-Fe-Al Alloy

Transition metal-based alloy nanostructures have emerged as promising catalysts for electrochemical water splitting, offering a potential solution to the growing demand for clean and renewable energy. Also, research on encapsulation engineering of alloy nanostructures using carbon matrices has recently advanced, presenting a new approach that combines the conductive properties of carbon matrices with an alloy structure to enhance electrochemical performance in water splitting. However, the specific roles of the alloy core, carbon shell, and their synergistic effect in improving electrochemical performance are still not well understood. In this paper, we report on the encapsulation of a ternary Co–Fe–Al alloy nanostructure using a carbon matrix and investigate its electrochemical oxygen evolution reaction (OER). The optimized carbon matrix-encapsulated Co0.3Fe0.2Al0.5 alloy catalyst demonstrated superior electrocatalytic activity for OER (achieving 250 mV at 10 mA cm−2) and long-term stability. Through density functional theory calculations, we also elucidate the crucial role of Al in enhancing the OER catalytic performance of the proposed carbon-encapsulated Co–Fe alloy catalyst. By comparing the free electron concentration and required applied potentials to trigger OER, we provide insights into the beneficial effects of incorporating Al into the Co–Fe alloy catalyst.

Highly wear resistant metal bond for diamond tool based on two-step reactive sintered Fe3Al

Metal bond diamond tools are regularly used in the machining of various hard and brittle materials. The mechanical properties and wear resistance of the metal bond are very important for the tool's life and machining performance. Herein, a low-cost and highly wear resistant Fe3Al bonded material for diamond tool was proposed. A novel two-step reactive sintering method, integrating short-term high-temperature reactive sintering and long-term low-temperature densification sintering, was proposed to prepare Fe3Al bond diamond tools. The effect of sintering temperature on the microstructure and mechanical properties of the Fe3Al bond was examined during one-step reactive sintering. The mechanical properties and tribological characteristics of the one-step and two-step reactive sintered Fe3Al and commercial Fe alloy bond were compared. The machining performance of the two-step reactive sintered Fe3Al bond diamond tool on sapphire was also examined and compared to that of a commercial Fe alloy bond diamond tool. The results showed that the relative density and mechanical properties of the Fe3Al bonded material were enhanced by increasing the sintering temperature during one-step reactive sintering. Moreover, the sample sintered at 1150-850 °C exhibited better mechanical properties and wear resistance compared to the one-step reactive sintered Fe3Al and commercial bond. The grinding ratio of the two-step reactive sintered Fe3Al bond diamond tool was 157 % higher than that of the commercial Fe alloy bond diamond tool.

Enhanced thermal stability of amorphous Al-Fe alloys by addition of Ce and Mn

The thermal stability of mechanically alloyed amorphous Al-Fe-based alloy powders, with nominal compositions Al82Fe16Ce2 and Al82Fe14Mn2Ce2, was investigated using differential scanning calorimetry (DSC), x-ray diffraction (XRD), and scanning electron microscopy (SEM) complemented by energy-dispersive x-ray spectroscopy (EDX). Analysis through DSC indicated that both Al82Fe16Ce2 and Al82Fe14Mn2Ce2 alloys undergo a two-stage crystallization process. Notably, the initial crystallization temperatures for the Al82Fe16Ce2 and Al82Fe14Mn2Ce2 alloys were determined to be approximately 525 °C and 550 °C, respectively. This high thermal stability is attributed to the delayed nucleation process induced by the presence of Ce and Mn within the Al-Fe matrix. During polymorphic crystallization, distinct phases such as β-AlFe, Al13Fe4 for Al82Fe16Ce2, and β-Al(Fe, Mn), Al13Fe4, Al10CeMn2 for Al82Fe14Mn2Ce2 were identified. Furthermore, post-annealing of these amorphous alloy powders at elevated temperatures of 600, 700, and 800 °C led to distinct morphological characteristics based on the alloy composition. For Al82Fe16Ce2, the particles preserved a nearly spherical morphology, with size distributions ranging from 1 to 5 μm. In contrast, for Al82Fe14Mn2Ce2, the particles exhibited an irregular shape with a broader size range of 1 to 15 μm.

Thermal stability of refined Al6(Fe, Mn) phase formed in laser powder bed fusion process

The addition of Mn in Al–Fe alloys stabilizes the Al6Fe metastable phase (orthorhombic structure, oC28) owing to the partial occupation of Fe sublattice sites by Mn atoms (formation of Al6(Fe, Mn) phase), thereby achieving superior high-temperature strength of Al–Fe–Mn ternary alloys that are manufactured via laser powder bed fusion (L-PBF) process. This study aimed to fundamentally understand the thermal stability of the refined Al6(Fe, Mn) phase formed in the L-PBF fabricated Al–2.5%Fe–2%Mn alloy in terms of a thermodynamic approach and the kinetics of morphological changes in the Al6(Fe, Mn) phase at elevated temperatures ranging from 200 to 500 ℃. The L-PBF processed samples showed a high hardness of approximately 125 HV due to the formation of numerous dispersoids of the Al6(Fe, Mn) phase with sizes of several tens of nanometers in the α-Al matrix containing concentrated solute elements of Fe and Mn. The hardness and microstructure were almost unchanged even after exposure to a high temperature of 200 ℃ for an extended period of 1000 h. Upon exposure to 300 ℃, nucleation and growth of the Al6(Fe, Mn) phase occurred locally, particularly at grain boundaries in the α-Al matrix. Such a local growth contributed to a reduction in hardness upon thermal exposure. Simultaneously, numerous nanoscale precipitates were formed in the α-Al matrix, resulting in a suppressed reduction in hardness. Contrary to the result of the thermodynamic calculations, the θ-Al13Fe4 phase was scarcely found even after long-term exposure to 500 ℃. The θ-phase formation was accompanied by the dissolution of the refined Al6Fe metastable phase for strengthening, which significantly reduced the hardness during thermal exposure. The suppressed θ-phase formation could be associated with the thermodynamically stable Al6(Fe, Mn) phase developed during the L-PBF process, which predominantly contributed to the high microstructural stability of the L-PBF fabricated Al–Fe–Mn alloy at elevated temperatures.

Carbothermal Reduction of Oil Shale Residue (OSR) in DC Electric Furnace to Prepare Si–Al–Fe Alloy

Carbothermal Reduction of Oil Shale Residue (OSR) in DC Electric Furnace to Prepare Si–Al–Fe Alloy

Development of Submicrometer Conical Surface Morphology on Nanometer-Thick Al–Fe Alloy Films under Various Conditions of Ion-Assisted Deposition onto Glass

Development of Submicrometer Conical Surface Morphology on Nanometer-Thick Al–Fe Alloy Films under Various Conditions of Ion-Assisted Deposition onto Glass

Formation of submicron conical morphology of the surface of nanometer-thick films of the Al–Fe alloy under various conditions of ion-assisted deposition on glass

The morphology, topography and wetting with distilled water of Al–1.5 at. % Fe alloy films with a thickness 25–90 nm, formed on glass by ion-assisted deposition using a resonance ion source of vacuum electric arc plasma, have been studied. Using scanning probe microscopy, it is shown that, depending on the mode and the time of deposition, the modification of films is accompanied by changes in longitudinal and transverse roughness parameters, as well as parameters – dimensionless complexes, the measurement of which makes it possible to quantitatively describe the processes of coning in the Al–Fe alloy/glass system. Thus, the arithmetic mean roughness of the films increases with deposition time in the range 20–40 nm. Under self-irradiation conditions, a transition from island-like film growth to layer-by-layer film growth was detected. The influence of the substrate topography on the longitudinal step parameters of the film topography has been established. The size and surface density of the microdroplet fraction particles are studied by scanning electron microscopy. The frequency distributions of the microdroplet fraction by size are satisfactorily approximated by the lognormal distribution. It is found that in the mode of irradiation with intrinsic ions, 60–70% of the microparticles have a size of up to 0.8 μm. For the first time, a double Gaussian function was used to approximate the distribution histograms of local maxima and minima of the film relief, which made it possible to increase the accuracy of the description compared to the normal law. The effectiveness of this approach in analyzing the structure formation of nanometer films at various stages of growth has been demonstrated. Using the bi-Gaussian surface model, the role of topographic characteristics in controlling the wetting of modified coatings is revealed. The mechanism of heterogeneous wetting of hydrophilic films in the Cassie mode with contact angles ranging 50°–80° is discussed. It is found that in the potential mode, with an increase in the deposition duration to 10 h, the distribution of the film relief is close to the normal law, and the formation of a developed submicron conical morphology on the surface leads to blended wetting.

Effect of Ni addition on the microstructure, conductivities and mechanical properties of as-cast Al-Fe alloys

In this study, the microstructure, conductivity and mechanical properties of as-casted Al-1Fe-xNi (x= 0, 1, 4, 6 and 10, wt%) alloys were systematically investigated. The results exhibited the Al-1Fe-xNi alloys mainly consist of α-Al, Al3Fe, Al3Ni, and Al9FeNi phase. With the increase of Ni addition, the size of α-Al grain decreases and the dimension of Al9FeNi phase increased. The hardness of the as-cast alloys raises with increasing Ni content, whereas the elongation and electrical conductivity decreases and the ultimate tensile strength (UTS) first increases and then decreases dramatically. The Al-1Fe-6Ni alloy exhibited the highest Q-value, which was approximately 11.27% higher than that of the Ni-free alloys. This mechanism of mechanical properties change occurs mainly due to slightly Ni effectively refines the α-Al phase, and the excessive Ni content leads to formation of coarse needle-like or lath-like Al9FeNi phase. Additionally, the grain refinement and precipitation of the second phase upon Ni addition impede electron movement, leading to a decrease in the electrical conductivity of the alloy. The corresponding ductile fracture morphologies of Al-1Fe-xNi alloys are also analyzed. These high-strength Al-1Fe-xNi alloys could be helpful for developing novel Al-Fe alloys with a high strength and ductility.

Toward the superior high-temperature strength of Al-5Fe alloy for powder bed fusion-laser beam: Stabilizing Al6Fe nanoprecipitate by Sc and Zr elements

Existing additively manufactured aluminum alloys exhibit unfavorable tensile strength above 200 °C due to the strengthening phase coarsening, microstructure instability and cracking. This paper designed a novel Al-5Fe-1Mg-0.6Sc-0.3Zr alloy for powder bed fusion using laser beam (PBF-LB) with tensile strength of 189 MPa at 400 °C, which is the highest value reported. The main strengthening phases of the alloy were Al6Fe particle and nano-scaled L12-Al3(Sc, Zr) precipitates. The exceptional high-temperature performance is attributed to high volume fraction (∼35%) of nanoprecipitates Al6Fe modified by Sc and Zr elements, showing enhanced thermal stability and refined particle dimension. The addition of Sc and Zr elements also significantly retards the phase transformation from Al6Fe to θ-Al13Fe4 and inhibits brittle θ phase growth during thermal exposure.

Achieving exceptional combination of strength and ductility in α+β diphase brass with harmonic structure

Heterogeneous structures are an effective way to give materials excellent combined strength-ductility properties. In this study, Cu–Zn–Al–Fe alloys were prepared by homogenizing and hot rolling-annealing, and an α+β diphase brass with harmonic structure was obtained by adjusting the content of Zn. The microstructure and mechanical properties of Cu-xZn-4Al-2.8Fe (x = 14, 20, 22.5, 24, wt%) were systematically investigated. The Cu–Zn–Al–Fe alloy has an α single-phase matrix at 14 wt% Zn and an α+β diphasic matrix at 20, 22.5, and 24 wt% Zn, all uniformly distributed with nano β(FeAl). A large amounts of twins are produced after rolling in α phase that has a low stacking fault energy. The Cu–20Zn–4Al-2.8Fe alloy exhibits a unique harmonic structure of the α-phase soft cores embedded in α+β biphasic hard shells. This alloy exhibits an excellent strength-ductility combination at room temperature, possessing an ultimate tensile strength of 473.7 MPa while maintaining a total elongation of 50.7%. Increases total elongation by 30.3% while maintaining high strength compared to homogeneous alloys (22.5 wt% Zn). While α single-phase alloy (14 wt% Zn) exhibits excellent plasticity (total elongation of 58.0%), their strength is not satisfactory (ultimate tensile strength of 419.7 MPa). In contrast, too much Zn (24 wt% Zn) produces a high proportion of β phase, which exhibits high strength (ultimate tensile strength of 507.9 MPa) and relatively poor plasticity (total elongation of 22.8%). Overall, the Cu–20Zn–4Al-2.8Fe alloy with a harmonic structure achieves excellent overall mechanical properties due to twinning, precipitation strengthening, and hetero-deformation induced (HDI) strengthening. This study provides an essential reference for designing heterogeneous structures of brass alloys.