Fe-Al Alloys Research Articles

Study on Al2O3/Fe-Al gradient coating assisted prepared by ionic liquid for Lead-Bismuth eutectic corrosion resistance

Alumina coating which has excellent corrosion resistance to lead–bismuth eutectic (LBE) is very promising to be used in future LBE cooling system. In this paper, the Al2O3/Fe-Al gradient coating is prepared on the surface of SIMP steel assisted by ionic liquid aluminum electroplating and subsequent heat treatments and selective oxidation. The protective Al2O3 layer is composed of much γ-phase and a small amount α-phase. The Fe-Al transition layer is mainly composed of FeAl alloy phase. After being exposed for 600 h to LBE at 600 °C, the coating still maintains intact and dense structure and good compatibility to the substrate, effectively preventing the substrate steel from the corrosion attack of LBE. While obvious LBE attack can be observed in the compared bare steel. Finally, to verify the possibility of this approach preparing Al2O3/Fe-Al coating on complex geometries, we have also successfully prepared this sort of coating on the inner surface of a steel tube, indicating that this coating has a great application potential in the future.

Experimental and theoretical study of the microstructure evolution and thermal-physical properties of hypereutectic Al–Fe alloys

Experimental and theoretical study of the microstructure evolution and thermal-physical properties of hypereutectic Al–Fe alloys

Phase Composition of Cast Intermetallic Fe–Al Alloys Produced by Self-Propagating High-Temperature Synthesis

Phase Composition of Cast Intermetallic Fe–Al Alloys Produced by Self-Propagating High-Temperature Synthesis

The Microstructure and Magnetic Properties of a Soft Magnetic Fe-12Al Alloy Additively Manufactured via Laser Powder Bed Fusion (L-PBF)

Soft magnetic Fe-Al alloys have been a subject of research in the past. However, they never saw the same reception in technical applications as the Fe-Si or Fe-Ni alloys, which is, to some extent, due to a low ductility level and difficulties in manufacturing. Additive manufacturing (AM) technology could be a way to avoid issues in conventional manufacturing and produce soft magnetic components from these alloys, as has already been shown with similarly brittle Fe-Si alloys. While AM has already been applied to certain Fe-Al alloys, no magnetic properties of AM Fe-Al alloys have been reported in the literature so far. Therefore, in this work, a Fe-12Al alloy was additively manufactured through laser powder bed fusion (L-PBF) and characterized regarding its microstructure and magnetic properties. A comparison was made with the materials produced by casting and rolling, prepared from melts with an identical chemical composition. In order to improve the magnetic properties, a heat treatment at a higher temperature (1300 °C) than typically applied for conventionally manufactured materials (850–1150 °C) is proposed for the AM material. The specially heat-treated AM material reached values (HC: 11.3 A/m; µmax: 13.1 × 103) that were close to the heat-treated cast material (HC: 12.4 A/m; µmax: 20.3 × 103). While the DC magnetic values of hot- and cold-rolled materials (HC: 3.2 to 4.1 A/m; µmax: 36.6 to 40.4 × 103) were not met, the AM material actually showed fewer losses than the rolled material under AC conditions. One explanation for this effect can be domain refinement effects. This study shows that it is possible to additively manufacture Fe-Al alloys with good soft magnetic behavior. With optimized manufacturing and post-processing, further improvements of the magnetic properties of AM L-PBF Fe-12Al may still be possible.

D03-ordered Fe3Al magnetic nanopowders synthesized by low oxygen induction thermal plasma

D03-ordered Fe3Al alloy with a large anomalous Nernst coefficient is considered as a promising candidate for a low-cost, flexible, and durable magneto-thermoelectric generator (MTG). To improve the thermoelectric performance of the more and more complex and smaller MTG modules, the incorporation of high-quality magnetic nanopowders (MNPs) is one solution. However, synthesizing fully chemically ordered MNPs without coalescence and/or oxidation with a conventional approach is challenging. In this study, we demonstrated, for the first time, D03-ordered (degree of ordering = 0.48) Fe3Al MNPs synthesized via a low oxygen thermal plasma process combined with appropriate post-annealing treatment. The resulting single crystalline MNPs are spherical in shape with a mean particle diameter of 116 ± 96 nm and exhibit a soft magnetic characteristic (saturation magnetization ≈ 112 emu/g; and coercivity ≈ 5 Oe at room temperature). The fundamental alloying mechanism during the thermal plasma process was investigated via numerical calculations, confirming that the alloying followed the route through the Fe-Al droplet. Our results will potentially aid the mass synthesis of chemical ordered MNPs for wearable energy harvesting and self-powered Internet of things applications.

Synthesis of FeSi-FeAl Composites from Separately Prepared FeSi and FeAl Alloys and Their Structure and Properties.

Composites consisting of iron aluminide and iron silicide phases were studied in this work. Powders of iron aluminide and iron silicide were prepared by mechanical alloying separately. Subsequently, they were blended in three different proportions and sintered by the SPS method under various conditions. After sintering, the composites are composed of FeAl and amounts of other silicides (Fe5Si3 and Fe3Si). Ternary Fe-Al-Si phases were not determined, even though their presence was predicted by DFT calculations. This disagreement was explained by steric factors, i.e., by differences in the space lattice of the present phases. Hardness and tribological properties were measured on composites with various weight ratios of iron aluminide and iron silicide. The results show that sintered silicides with the matrix composed of iron aluminide reach comparable hardness to tool steels. The composites with higher mass ratios of iron aluminide than silicide have higher hardness and better tribological properties.

In-situ synthesis of Fe-Al intermetallic via arc additive manufacturing with cable-type wire

A novel arc additive manufacturing process using cable-type wire (CWAAM) was successfully used for the first time to fabricate Fe3Al intermetallic with 33 at% aluminum content. The microstructure and mechanical properties of the in situ prepared Fe3Al alloy were evaluated through optical microstructural characterization, X-ray diffraction for phase analysis, electron dispersion spectroscopy for chemical composition analysis, hardness testing, and compression testing. The results indicate that compared with Fe3Al alloy prepared by traditional sintering or mechanical alloying methods, the Fe3Al alloy prepared by CWAAM exhibits relatively uniform distribution of alloying elements and higher compressive strength.

Rapid and effective removal of copper, nitrate and trichloromethane from aqueous media by aluminium alloys

Zero-valent iron (ZVI) has been extensively studied for its efficacy in removing heavy metals, nitrate, and chlorinated organic compounds from contaminated water. However, its limited effectiveness due to rapid passivation and poor selectivity is prompting for alternative solutions, such as the use of aluminium alloys. In this study, the efficacy of five distinct aluminium alloys, namely Al–Mg, Al–Fe, Al–Cu, and Al–Ni, each comprising 50 % Al by mass at a concentration of 10 g/L, was assessed using copper, nitrate and trichloromethane (TCM) as model contaminants. Results show that chemical pollutants reacted immediately with Al–Mg. On the contrary, the remaining three alloys exhibited a delay of 24 h before demonstrating significant reactivity. Remarkably, Al–Mg alloy reduced nitrate exclusively to ammonium, indicating minimal preference for nitrate reduction to N2. In contrast, the Al–Cu, Al–Ni, and Al–Fe alloys exhibited N2 selectivity of 3 %, 5 %, and 19 %, respectively. The removal efficiency of copper, nitrate and TCM reached 99 % within 24 h, 95 % within 48h and 48 % within 48h, respectively. Noteworthy findings included the correlation between Fe concentration within the Al–Fe alloy and an increased N2 selectivity from 9.3 % to 24.1 %. This resulted in an increase of Fe concentration from 10 % to 58 % albeit with a concurrent reduction in reactivity. Cu2+ removal by Al–Fe alloy occurred via direct electron transfer, while the removal of nitrate and TCM was facilitated by atomic hydrogen generated by the alloy's hydrolysis. Intriguingly, nitrate and TCM suppressed Cu2+ reduction, whereas Cu2+ improved nitrate reduction and TCM degradation. These findings demonstrate the great potential of Al–Mg and Al–Fe alloys as highly efficient agents for water remediation.

Quantitative three-dimensional imaging of chemical short-range order via machine learning enhanced atom probe tomography

Chemical short-range order (CSRO) refers to atoms of specific elements self-organising within a disordered crystalline matrix to form particular atomic neighbourhoods. CSRO is typically characterized indirectly, using volume-averaged or through projection microscopy techniques that fail to capture the three-dimensional atomistic architectures. Here, we present a machine-learning enhanced approach to break the inherent resolution limits of atom probe tomography enabling three-dimensional imaging of multiple CSROs. We showcase our approach by addressing a long-standing question encountered in body-centred-cubic Fe-Al alloys that see anomalous property changes upon heat treatment. We use it to evidence non-statistical B2-CSRO instead of the generally-expected D03-CSRO. We introduce quantitative correlations among annealing temperature, CSRO, and nano-hardness and electrical resistivity. Our approach is further validated on modified D03-CSRO detected in Fe-Ga. The proposed strategy can be generally employed to investigate short/medium/long-range ordering phenomena in different materials and help design future high-performance materials.

Shape memory properties and microstructure evolution of Cu–Al–Fe alloys with different Fe contents

Shape memory properties and microstructure evolution of Cu–Al–Fe alloys with different Fe contents

Hot deformation behavior of a Fe3Al–Ta alloy in the B2-order regime

In the present work, the hot deformation behavior and the corresponding microstructure evolution of an Fe–25Al-1.5Ta (at.%) alloy in the B2-phase field were investigated. Uniaxial compression tests were carried out in a strain rate range from 0.0013 s−1 to 1 s−1 and in a temperature range from 800 °C to 850 °C, where an ordered B2–FeAl matrix phase along with a C14 - (Fe, Al)2Ta Laves phase was confirmed by X-ray diffraction. A dynamic material model was applied to predict the safe and damaging processing windows. The underlying flow softening mechanisms were characterized using scanning electron microscopy and electron-backscatter diffraction. The flow stress-strain curves mostly showed a broad maximum followed by a slight decrease in stress until a steady stress was reached. The optimum processing window for the studied alloy was located at 850 °C/0.0013 s−1, where the efficiency of power dissipation (η) and strain rate sensitivity (m) reached 50% and 0.25, respectively. The processing map also showed a domain of flow instability, resulting from cracking, in the range of lower temperatures and higher strain rates (800 °C/1 s−1). The microstructural analyses confirmed a combination of dynamic recovery (DRV) and dynamic recrystallization (DRX) over the entire range of deformation conditions tested. The current study reveals a well-suited parameter range to achieve a high degree of hot deformability in Fe–Al alloys at significantly lower temperatures than those typically used. This may contribute to optimizing the thermomechanical processing of Fe–Al alloys and reducing energy consumption in industrial forging operations.

Structure and Electrical Properties of AlFe Matrix Composites with Graphene

Composites based on Al-Fe alloys and reinforced with three-layer graphene sheets were synthesized “in situ” under a layer of molten salts. Composites containing 0.12 wt.% graphene were subjected to severe plastic deformation via high-pressure torsion. SEM and TEM were used to study the morphological and size characteristics of the composite structure in the as-cast and deformed states. Herein, it is shown that severe plastic deformation leads to the deformation-induced dissolution of iron-containing aluminides with the formation of a supersaturated Al solid solution with a submicrocrystalline structure. The hardness and electrical properties of the graphene composites were measured in different structural states and compared to the characteristics of the matrix alloy.

Morphological and semiconductive properties of the anodic oxide layers made on Fe3Al alloy by anodizing in tartaric-sulfuric acid mixture

It has recently been found that the anodizing of FeAl alloys allows the formation of iron-aluminum oxide layers with interesting semiconducting properties. However, the lack of systematic research on different anodizing regimes is hampering their full exploitation in numerous photoelectrochemical-related applications. This study address, for the first time, the systematic effect of the electrolyte composition on the formation of self-ordered oxide films by anodizing on cast Fe3Al alloy. The Fe3Al alloy was anodized in 3 electrolytes with different water-ethylene glycol (EG) ratios (pure water, 25 vol.%-EG, and 50 vol.%-EG solutions) at a constant tartaric-sulfuric acids concentration, different voltages (10–20 V) and treatment times (2–60 min). After anodizing, all anodic oxide layers were annealed at 900 °C to form semiconductive iron-aluminum crystalline phases. Conventional techniques were used to systematically ascertain the morphological (SEM/EDS, XRD, eddy-current measurements) and semiconductive (UV–VIS reflectance spectroscopy) properties of these oxide layers. The results confirmed the formation of homogeneous and self-ordered anodic oxide layers at 10 and 15 V, regardless of the electrolyte composition. Namely, anodic films formed in electrolytes containing EG showed lower pore sizes, growth rates, and film thicknesses than those anodic films formed in the aqueous-based electrolyte. The annealing post-treatment results in different Fe-Al oxides (FexOy, FeAl2O4, etc.) with superior band gap values than those for non-annealed films.

Modified embedded atom method interatomic potentials for the Fe-Al, Fe-Cu, Fe-Nb, Fe-W, and Co-Nb binary alloys

In this study, we developed interatomic potentials for the Fe-Al, Fe-Cu, Fe-Nb, Fe-W, and Co-Nb binary systems using the second nearest-neighbor modified embedded-atom method (2NN MEAM) formalism. The interatomic potentials were parameterized through fitting to available data on essential physical properties such as enthalpies of formation, structural parameters, and elastic constants. The fitted interatomic potentials are capable of accurately reproducing these properties, demonstrating a satisfactory level of concordance with data collected through experimentation, CALPHAD evaluations, and first-principles calculations. These potentials can be merged with existing MEAM potentials to study the physical metallurgy of multicomponent alloys such as FeCo-X (X = Al, Cu, Nb and W) and high entropy alloys (HEA), enabling deeper understanding of their unique properties at the atomic scale.

Influence of atomic ordering and cerium doping on magnetostrictive Fe-Al alloys

Magnetostrictive iron-aluminum alloys can be a low-cost, mechanically stable alternative to iron-gallium and rare earth-iron alloys. The magnetostrictive performance of polycrystalline Fe-Al (alfenol) with 13–24 at. % Al was investigated, studying the role of compositional variation and thermal history. It was found that rapid cooling enhances the magnetostrictive response, and peak magnetostriction was found in Fe78Al22 by high temperature annealing followed by quenching. Synchrotron diffraction enabled a direct correlation of magnetostrictive behavior and the transition from short-range order to long-range ordered cluster domains in the material which can be suppressed by rapid cooling. Following recent success of doping Fe-Ga with rare earth elements, we investigated the influence of Ce doping on improving magnetostriction and found that Fe-Al shows negligible solubility for cerium, inhibiting potential magnetostriction enhancement. Our results illustrate the complex interplay between phase stability, ordering, and optimized magnetostrictive response.

Nitrate Reduction through Al-Fe Alloy Catalyst: Effects of Activation Pre-Treatment Method and Alloy Type

This study explored the nitrate reduction by Al-Fe alloy. The nitrate conversions of fresh, 30-day and 90-day alloys were 78.1%, 42.8% and 9.5%, respectively. Water activation promoted the reducing ability of the alloy (98% nitrate removal), which was higher than that of copper deposited alloy (66%) and H2-reducing/acid/alkali/Cl− activated alloy (no enhancement). The effects of pre-treatments on the surface O fraction changes confirmed the activation results. With increased Fe:Al mass ratio in the alloy, nitrate conversion initially decreased and then increased again, verifying the proposed electron-donator activity of Al or Fe in alloys. Al-Fe30 had the highest NO3− conversion and Al13Fe4 content, so Al-Fe30 was selected. Significant differences in conversion were observed in alloy usages of 5–10 and 15–30 g/L. High reduction performance (nitrate below the detection limit and 19.1% N2 selectivity) was achieved under the optimal conditions: 15 g/L Al-Fe30, 150 min reaction and without pH adjustment. The rate constants of nitrate removal, nitrogen generation and ammonia generation were k1 = 1.43 × 10−2, k2 = 3.41 × 10−2 and k3 = 10.58 × 10−2 min−1, respectively. The value of (k2 + k3)/k1 was 10, indicating that the conversion of nitrate into nitrite was the rate-determining step. The repetition reaction was performed, and the rate constant decreased as the reaction step was repeated.

Effects of Material Structure on Stress Relaxation Characteristics of Rapidly Solidified Al-Fe Alloy.

An Al-Fe alloy which was produced by hot extrusion of rapidly solidified powder is a possible solution to substitute copper-based electrical conductor material due to its high strength and high electrical conductivity. However, the stress relaxation characteristic-an essential parameter as a conductor material-and the effect of the material structure have not been reported, which was the aim of the present paper. An Al-5%Fe alloy was selected as the test material. The material structures were controlled by hot extrusion practice, annealing, and cold rolling. The Al-Fe intermetallic compound particles controlled the residual stress after the stress relaxation test via the Orowan mechanism. Decreasing the mean inter-particle distance reduces the electrical conductivity. The increase in the number of dislocations by the cold rolling increased strength at room temperature without changing electrical conductivity; however, it did not have a positive effect on the stress relaxation characteristics. The stress relaxation characteristics and the electrical conductivity of the Al-Fe alloy were superior to conventional C52100 H04 phosphor bronze when compared with the case of the same mass.

Effect of in-situ generated Fe3AlC0.5 on the microstructure and mechanical property of twin-wire directed energy deposition-arc fabricated Fe3Al based iron aluminide

Fe3Al-based iron aluminide alloys are known for their satisfactory resistance to corrosion, oxidation, and sulfidation at both ambient and elevated temperatures. However, the brittleness induced by the intermetallic nature of these alloys at room temperature significantly increases the manufacturing costs. To address this issue, a recent innovation called twin-wire directed energy deposition-arc (TW-DED-arc) technique has been developed to fabricate binary Fe3Al alloys with enhanced flexibility and cost-effectiveness. Building upon the feasibility validation of this technique, the present research aims to improve mechanical properties of TW-DED-arc fabricated Fe30Al alloy by in-situ generation of Fe3AlC0.5 precipitates within Fe3Al matrix. The experimental results demonstrate the successful production of the target Fe-30Al-0.3C-1Si-1Mn alloy. The reinforcement Fe3AlC0.5 precipitates exhibit good adherence to Fe3Al matrix, effectively increasing the tensile strength by nearly 15%. During tensile fracture, Fe3AlC0.5 precipitates are observed to obstruct crack propagation. Higher magnification characterization reveals clear dislocation entanglement occurring at Fe3AlC0.5 precipitate, confirming this phenomenon. Furthermore, preferential precipitation of Fe3AlC0.5 at grain boundaries induces clean areas adjacent to the grain boundaries. This has a dual effect: strengthening the grain boundaries and guiding crack propagations.

Deformation behaviour of a cast Fe–19Al–5Cr-0.04Zr alloy at room and intermediate temperatures

The mechanical properties of a Fe–19Al (at.%) alloy containing 5 at.% Cr as the main alloying element are presented and discussed. While the alloy behaves brittle at room temperature and 100 °C, tensile stress-strain curves at temperatures between 200 °C and 500 °C show strain hardening recovery effects similarly to those of fcc twinning induced plasticity (TWIP) steels. It is supposed that a combination of dislocation glide and formation of internal boundaries in the submicron range leads to similar strain hardening stages at intermediate temperatures (200 °C–500 °C) in the FeAl alloy as usually observed in TWIP steels at room temperature. The maximum strain hardening rate after recovery reaches very high values of about G/19 at 400 °C. Low-cycle fatigue (LCF) tests at 400 °C and 500 °C up to strain amplitude values of 0.6% and stress-relaxation tests do not reveal high back stresses or pseudoelasticity in the FeAl alloy. This indicates that the deformation structures responsible for the strain hardening rate recovery remain stable upon stress relief.

Elucidation on the correlation between thermal stability of Al13Fe4 intermetallic phase and mechanical properties of the Al-Fe alloy fabricated via friction stir alloying

Al-Fe alloy containing nanosized Al13Fe4 phase was fabricated by the solid-state multiple pass friction stir alloying (FSA) technique and subjected to heat treatment at different time-temperature conditions. During annealing, the diffusion of Fe atoms leads to the necking and fragmentation of the coarse plate shape Al13Fe4 IMC phase resulting in its spheroidization. However, as the annealing time is extended, the spheroidized Al13Fe4 phase undergoes coarsening and grows predominantly along a specific plane. This growth process transforms the originally spherical shape into an elliptical or small plate-like morphology. The grain size was insignificantly affected by the annealing time and temperature owing to the grain boundary pinning by the nanometric-sized IMC phase. The ultimate tensile strength of the Al-Fe alloy (149 MPa) is improved significantly at the annealing conditions of 200 °C/4hrs (165 MPa), 200 °C/6hrs (167 MPa), and 300 °C/2hrs (163 MPa). The improved UTS is attributed to the increased isotropic work hardening owing to the reduced IMC particle size and mean interparticle spacing in the Al-Fe alloy. The lowest work hardening rate is observed in the specimen annealed at 200 °C for 2 hrs (largest particle size) which is attributed to the stored energy in the material due to severe plastic deformation (SPD) associated with the FSA. The correlation between the work hardening rate, IMC particle size, and mean interparticle spacing at various annealing conditions are established.