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This study investigated the microstructural constituents and forming properties of alloy Al-1.4 wt.% Fe with different additions of Ce and/or La. The addition of rare earth (RE) elements to aluminum alloys improves their microstructures in their as-cast and heat-treated states. RE additions and appropriate heat treatment also improve their mechanical properties. The influence of the homogenization process on the microstructure and forming properties of Al-1.4 wt.% Fe alloy with various additions of Ce and/or La was investigated. When homogenizing the Al-1.4 wt.% Fe alloy at 580 °C, the majority of the homogenization process is completed after 6 h; at 600 °C, after about 5 h; and at 620 °C, after about 4 h. In the micro-alloyed Al-1.4 wt.%–Fe alloy, α-Al, stable Al13Fe4 phases in an agglomerated form, La-containing phases in a spherical form, and Ce-containing phases in a rod-shaped form are present after homogenization. The addition of La was shown to be advantageous as a micro-addition to Al–Fe alloys. Its forming properties show that the combination of Ce and La is the most favorable addition, whereby the homogenization process is fully optimized. [ABSTRACT FROM AUTHOR]

Cellular structures (i.e., solidification cells) are a unique feature within alloys fabricated through rapid solidification, such as laser-powder bed fusion (L-PBF). Ever since the report of these structures’ beneficial effects on the material's mechanical properties, numerous studies have been devoted to the understanding of their formation mechanisms. Yet, the integrity and stability of the cellular structures are often less investigated, despite their significance on property interpretation and evolution. In this work, a stepwise in-situ heating transmission electron microscopy (TEM) experiment was performed on the exemplary LPBF-fabricated AlFeSiMoZr alloy. A critical threshold of 325 °C was identified, beyond which the cellular structures start to decompose in conjunction with precipitate coarsening. Preferred precipitate nucleation sites and their subsequent coarsening kinetics were determined and presented. Nanometer-sized crystalline embryos (3.81 ± 0.66 nm) were discovered within the cellular structure boundaries in their as-built condition, offering new insights on the precipitate formation and evolution at elevated temperatures.

The morphology, topography, and wettability with distilled water of Al–1.5 at % Fe alloy films with thicknesses of 25–90 nm are investigated. These films are formed on glass by ion-assisted deposition using a resonance ion source of vacuum arc plasma. Scanning probe microscopy reveals that the longitudinal and transverse roughness parameters, as well as dimensionless complexes, vary depending on the deposition mode and time. Measurement of these dimensionless parameters yields a quantitative description of cone formation processes in the Al–Fe/glass system. The mean roughness of the films increases in the range of 20–40 nm within the duration of deposition. Under self-irradiation conditions, the transition from island growth of the films to layered growth is observed. The effect of the substrate relief on the longitudinal step parameters of the film topography is found. Scanning electron microscopy is employed to examine the size and surface density of microdroplet-fraction particles. The size-frequency distributions of the microdroplet fraction are satisfactorily approximated by a lognormal distribution. Under self-ion irradiation conditions, 60–70% of particles comprising the microdroplet fraction are up to 0.8 µm in size. For the first time, a double Gaussian function is employed to approximate histograms of the distribution of relief features in the films, improving the accuracy in the description compared to a normal distribution law. The effectiveness of this approach in analyzing the structural formation of nanoscale films at various growth stages is demonstrated. By employing a bi-Gaussian model of the surface, the role of topographic characteristics in controlling the wetting of modified coatings is determined. The mechanism of the heterogeneous wetting of hydrophilic films in the Cassie state with contact edge angles of 50°–80° is discussed. In the potential mode, with an increase in deposition duration up to 10 h, the relief distribution of the films approximates a normal distribution, and the development of a submicrometer conical morphology on the surface leads to mixed wetting. [ABSTRACT FROM AUTHOR]

This study investigated the microstructural constituents and forming properties of alloy Al-1.4 wt.% Fe with different additions of Ce and/or La. The addition of rare earth (RE) elements to aluminum alloys improves their microstructures in their as-cast and heat-treated states. RE additions and appropriate heat treatment also improve their mechanical properties. The influence of the homogenization process on the microstructure and forming properties of Al-1.4 wt.% Fe alloy with various additions of Ce and/or La was investigated. When homogenizing the Al-1.4 wt.% Fe alloy at 580 °C, the majority of the homogenization process is completed after 6 h; at 600 °C, after about 5 h; and at 620 °C, after about 4 h. In the micro-alloyed Al-1.4 wt.%–Fe alloy, α-Al, stable Al13Fe4 phases in an agglomerated form, La-containing phases in a spherical form, and Ce-containing phases in a rod-shaped form are present after homogenization. The addition of La was shown to be advantageous as a micro-addition to Al–Fe alloys. Its forming properties show that the combination of Ce and La is the most favorable addition, whereby the homogenization process is fully optimized.

This paper features the changes in microstructure and properties of an Al–Fe alloy produced by casting with different solidification rates followed by severe plastic deformation and rolling. Particularly, different states of the as-cast Al–1.7 wt.% Fe alloy, obtained by conventional casting into a graphite mold (CC) and continuous casting into an electromagnetic mold (EMC), as well as after equal-channel angular pressing and subsequent cold rolling, were studied. Due to crystallization during casting into a graphite mold, particles of the Al6Fe phase are predominantly formed in the cast alloy, while casting into an electromagnetic mold leads to the formation of a mixture of particles, predominantly of the Al2Fe phase. The implementation of the two-stage processing by equal-channel angular pressing and cold rolling through the subsequent development of the ultrafine-grained structures ensured the achievement of the tensile strength and electrical conductivity of 257 MPa and 53.3% IACS in the CC alloy and 298 MPa and 51.3% IACS in the EMC alloy, respectively. Additional cold rolling led to a further reduction in grain size and refinement of particles in the second phase, making it possible to maintain a high level of strength after annealing at 230 °C for 1 h. The combination of high mechanical strength, electrical conductivity, and thermal stability can make these Al–Fe alloys a promising conductor material in addition to the commercial Al–Mg–Si and Al–Zr systems, depending on the evaluation of engineering cost and efficiency in industrial production. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper features the changes in microstructure and properties of an Al–Fe alloy produced by casting with different solidification rates followed by severe plastic deformation and rolling. Particularly, different states of the as-cast Al–1.7 wt.% Fe alloy, obtained by conventional casting into a graphite mold (CC) and continuous casting into an electromagnetic mold (EMC), as well as after equal-channel angular pressing and subsequent cold rolling, were studied. Due to crystallization during casting into a graphite mold, particles of the Al6Fe phase are predominantly formed in the cast alloy, while casting into an electromagnetic mold leads to the formation of a mixture of particles, predominantly of the Al2Fe phase. The implementation of the two-stage processing by equal-channel angular pressing and cold rolling through the subsequent development of the ultrafine-grained structures ensured the achievement of the tensile strength and electrical conductivity of 257 MPa and 53.3% IACS in the CC alloy and 298 MPa and 51.3% IACS in the EMC alloy, respectively. Additional cold rolling led to a further reduction in grain size and refinement of particles in the second phase, making it possible to maintain a high level of strength after annealing at 230 °C for 1 h. The combination of high mechanical strength, electrical conductivity, and thermal stability can make these Al–Fe alloys a promising conductor material in addition to the commercial Al–Mg–Si and Al–Zr systems, depending on the evaluation of engineering cost and efficiency in industrial production.

Homogenization heat treatment is the first step in the processing of aluminium alloys, which for most alloys is carried out before any deformation process. Homogenization is performed to counteract microsegregation, which is the result of non-equilibrium solidification caused by diffusion rate differences between solid and liquid states during solidification. Special attention must also be paid to the impact of homogenization on changes in the morphology of iron-based constituents which are known to adversely affect formability. For the purpose of this work, a hypoeutectic Al–Fe alloy containing 1.1 mass/% Fe was homogenized at 600 °C for up to 12 h in an electric furnace. After the homogenization heat treatment, differential scanning calorimetry (DSC) was performed, comparing the homogenized samples with the sample in the as-cast state. The results were compared with thermodynamic calculations using Thermo-Calc software in order to determine the differences between the microstructure in the equilibrium and non-equilibrium state. All samples were analysed by optical and electron microscopy, and the intermetallic phases were qualitatively evaluated by both methods. In addition, energy-dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) were required to determine the type of phases present in all experimental samples and a difference between the as-cast and homogenized state was found. The presence of metastable phases in the as-cast state and the transformation of such phases during the homogenization process was confirmed. A homogenization process, which lasted 12 h at 600 °C, was also performed with a DSC instrument. The experiment confirmed a greater heat transfer at the beginning of the homogenization process, which is consistent with all previous analyses. All results showed that after 10 h of homogenization the effects of non-equilibrium solidification in this alloy were sufficiently counteracted. [ABSTRACT FROM AUTHOR]

This study focuses on the difference in microstructural features and physical properties of Al-2Fe and Al-4Fe alloys subjected to large plastic straining. The difference in the intermetallic particle morphology in the initial state is shown to be a key parameter influencing the particle and grain fragmentation process and, as a result, the properties of these two alloys. We demonstrate that the shape and average size of Al-Fe intermetallic particles provide stronger effect on the microstructure evolution during high pressure torsion (HPT) than their volume fraction. The formation of Fe supersaturated solid solution in Al in these two alloys during deformation is discussed in connection to the morphology of the intermetallic phase. The major microstructural attributes, responsible for the solid solution formation, are highlighted.

Al-Fe alloys with high Fe content and spherical Al 3 Fe phase have been successfully fabricated via the thermal plasma jet (TPJ) approach. The main size of spherical Al 3 Fe phase ranges from 10–15 μm and the minimum value is below 8 μm, and the average size of irregular Al 3 Fe phase typically bellow 20 μm. In this work, Fe content of the as-fabricated Al-Fe alloys are 5 wt.%, 10 wt.% and 15 wt.%, respectively. Microstructure characterization indicated that almost all of the Al 3 Fe phase distributed evenly on the Al matrix. A possible formation mechanism of spherical Al 3 Fe prepared via TPJ approach was tentatively proposed after investigating two different conditions with and without plasma arc heating. Meanwhile, we found that the morphology of Al 3 Fe could be modified via plasma arc in the preparation process. [ABSTRACT FROM AUTHOR]

High‐pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high‐pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high‐pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High‐pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys. [ABSTRACT FROM AUTHOR]

Al-Fe alloys, with large amounts of sphere-like structures, few plate-like structures, and little needle-like structures of micron scale second phase have been successfully prepared via a new type of solid-liquid mixture approach combined with plasma arc heating (PAH). The authors have obtained Al-Fe alloys with iron content of 0-15%, which is of extremely significance that thermal plasma jet (TPJ) breaks through the limitation of low iron content in Al-Fe alloys. Microstructures characterization indicates that not only the microstructures of Al-Fe alloys are refined, but also the morphologies are optimized. Meanwhile, sharp corners of iron powders are rounded off and impurities are removed under the action of PAH, which is important for improving mechanical property of Al-Fe alloys. And then, the effects of various parameters including PAH, iron content, and melt temperature on the microstructures and mechanical performance are systematically investigated. The possible influence mechanisms of parameters are investigated and put forward, and appropriate parameters have been obtained during the processing of Al-Fe alloys via TPJ. [ABSTRACT FROM AUTHOR]

In this paper, we report on the influence of rapid solidification and severe plastic deformation on the solid solubility of Fe in Al. Atom probe tomography, for the first time, was performed on fine (3–4 μm diameter) and coarse (~100 μm) as-atomised Al-5 at.% Fe powder and cryomilled Al-5 at.% Fe powder. The atomised powders exhibited negligible Fe in solution with Al, whereas the cryomilled powder contained ~2 at.% Fe in solution. Moreover, our results suggest that severe plastic deformation is preferable to atomisation/rapid solidification for increasing the non-equilibrium solid solubility of Fe in Al. [ABSTRACT FROM AUTHOR]

Achieving both high strength and ductility is challenging in additive manufacturing of Al alloys using the laser powder bed fusion (L-PBF) process by altering the laser conditions to control the microstructural characteristics. The current work focuses on the influence of varying laser energy density (ED), which is adjusted by different sets of laser power (P) and scan speed (v), on the microstructure-tensile property relationships of the L-PBF-fabricated Al–2.5%Fe alloy under varying laser conditions (P = 204–230 W, v = 450–600 mm/s) with a fixed powder layer thickness (t = 30 μm) and hatch distance (h = 30 μm). With increasing ED (= P / v · t · h), a slight increase in the average size of the columnar α-Al grains was found in the experimental samples concurrently with a higher fraction of <001>-oriented grains. Nanosized particles of the Al 6 Fe phase with an increased tendency to interconnect were observed in the matrix inside the melt pool, and the θ phase formed within the submicron-sized cellular structure along the melt pool boundaries (MPBs). A low tensile ductility, induced by the local microstructural inhomogeneities across MPBs, was found in all specimens tensile-deformed along the building direction, which was characterized by a preference fracture along the MPBs. At higher applied ED , the tensile ductility of the experimental Al–2.5Fe alloy was significantly improved with only a slight decrease in tensile strength. The difference in concentration of Fe across the MPBs in the matrix was also moderately diminished, which is consistent with the reduced local difference in microhardness across the MPBs under higher ED conditions. Therefore, the present results demonstrate that local microstructural inhomogeneities across MPBs can be controlled by the laser conditions, thereby producing both high strength and good ductility in the L-PBF processed Al–Fe alloys. • Effect of laser energy density on microstructure and tensile properties was studied. • Microstructural inhomogeneities across melt pool boundaries (MPBs) were altered. • High energy density leads to reduced microhardness differences across MPBs. • High tensile strength and good ductility were obtained by high energy density. [ABSTRACT FROM AUTHOR]

Al-Fe alloys with concentrations of iron of up to 50 at % have been produced from elemental powders using severe plastic deformation by high-pressure torsion. The synthesized alloys were studied using X-ray diffraction structural analysis and transmission and scanning electron microscopy, as well as microhardness measurements. It has been found that the grain size depends on both the degree of plastic deformation and the concentration of iron in the alloy. Plastic deformation by high-pressure torsion results in the mutual dissolution of iron and aluminum atoms. At room temperature, the solubility of iron in aluminum reaches ~1 at %. The dissolution of aluminum in the iron lattice leads to the formation of a disordered FeAl solid solution. With an increase in the concentration of iron in the alloy, its microhardness monotonically rises to a value of 3.4 GPa. [ABSTRACT FROM AUTHOR]

Abstract: Laser beam welding has recently been incorporated into the fabrication process of aircraft and automobile structures. Surface roughness is an important parameter of product quality that strongly affects the performance of mechanical parts, as well as production costs. This parameter influences the mechanical properties such as fatigue behavior, corrosion resistance, creep life, etc., and other functional characteristics such as friction, wear, light reflection, heat transmission, lubrification, electrical conductivity, etc. The effects of laser surface remelting (LSR) on the morphology of Al–Fe aerospace alloys were examined before and after surface treatments, using optical microscopy (OM), scanning electron microscopy (SEM), low‐angle X‐ray diffraction (LA‐XRD), atomic force microscopy (AFM), microhardness measurements (Vickers hardness), and cyclic voltammetry. This analysis was performed on both laser-treated and untreated sanded surfaces, revealing significant differences. The LA‐XRD analysis revealed the presence of alumina, simple metals and metastable intermetallic phases, which considerably improved the microhardness of laser‐remelted surfaces. The morphology produced by laser surface remelting enhanced the microstructure of the Al–Fe alloys by reducing their roughness and increasing their hardness. The treated surfaces showed passivity and stability characteristics in the electrolytic medium employed in this study. [Copyright &y& Elsevier]

Abstract: The aim of the present investigation was to contribute to provide a basis for understanding how to control solidification parameters, microstructure and mechanical strength of Al–Fe alloys. Upward directional solidification experiments have been carried-out with commercially pure Al and Al–0.5wt.% Fe, Al–1.0wt.% Fe and Al–1.5wt.% Fe alloys. The tensile tests results have been correlated to cell spacing (λ 1), since cellular growth has prevailed along all obtained Al–Fe castings. The used casting assembly was designed in such way that the heat was extracted only through the water-cooled system at the bottom of the casting. In order to investigate the nature of Al–Fe intermetallic fibers, they were extracted from the aluminum-rich matrix by using a dissolution technique. These fibers were then investigated by SEM-EDAX microscopy. It was found that the ultimate tensile strength, yield tensile strength and elongation increase with decreasing cell spacing. The highest ultimate tensile strength was that obtained for the most refined microstructure, i.e. for the Al–1.5wt.% Fe alloy sample, where a higher density of eutectic fibers was found distributed in a more homogeneous way along the casting section due to lower cell spacings. In contrast, the elongation was found to decrease with increasing solute content. [Copyright &y& Elsevier]

Hydrogen is becoming important clean energy while zerovalent iron (ZVI) and ferroferric oxide are of great interest to many applications including environmental remediation and chemical catalysis. Here, we report production of hydrogen, zerovalent iron and ferroferric oxide octahedron by etching Al–Fe alloys using NaOH solutions. The rate of hydrogen generation increased with increasing NaOH concentration and the alloy's particle size and decreasing the alloy's Fe concentration. Alkaline etching Al–Fe alloy particles of 425–850 μm produced 19–53 μm ZVI particles, which had paralleled ravines of 0.2–0.3 μm wide on the surface and possessed specific surface areas of 30–70 m2/g. The microscale ZVI was highly active for the removal of a model pollutant acid orange 7 from water. After 3–6 h ageing in the alkaline etching solution, the microscale ZVI particles were transformed to octahedral ferroferric oxide with saturation magnetization of 68.2 emu/g and residual magnetization of 13.2 emu/g and a coercive force of 330 Oe. This study provides a new approach for a facile synthesis of highly active ZVI and octahedral ferroferric oxide along with on-board generation of hydrogen from Al–Fe alloys. [Display omitted] • Hydrolysis of Al–Fe alloys produces hydrogen and active zero valent iron (aZVI) particles. • aZVI particles have specific surface areas of 30–70 m2/g. • aZVI outperforms conventional nano-ZVI for pollutant removal from water. • Ageing aZVI in the hydrolysis solution generates octahedral Fe 3 O 4 crystals. [ABSTRACT FROM AUTHOR]

This study focuses on the difference in microstructural features and physical properties of Al-2Fe and Al-4Fe alloys subjected to large plastic straining. The difference in the intermetallic particle morphology in the initial state is shown to be a key parameter influencing the particle and grain fragmentation process and, as a result, the properties of these two alloys. We demonstrate that the shape and average size of Al-Fe intermetallic particles provide stronger effect on the microstructure evolution during high pressure torsion (HPT) than their volume fraction. The formation of Fe supersaturated solid solution in Al in these two alloys during deformation is discussed in connection to the morphology of the intermetallic phase. The major microstructural attributes, responsible for the solid solution formation, are highlighted. [ABSTRACT FROM AUTHOR]