FeAl Particles Research Articles

Aluminum-Modified Plasma Nitriding with High Efficiency and Enhanced Performance

Aluminum-modified plasma nitriding was developed in this research by the addition of a few FeAl particles around samples of 42CrMo middle carbon alloy steel during plasma nitriding. The goal of this study was to enhance nitriding efficiency and the combined performance of the steel. The research results show that nitriding efficiency was greatly enhanced, by about 6 times, with the effective hardening layer rising from 224 μm to 1246 μm compared with traditional plasma nitriding at 520 °C/4 h. More importantly, the compound layer increased just a little bit, from 11.64 μm to 14.32 μm, which remarkably reduced the ratio of the compound layer’s thickness to the effective hardening layer’s thickness, thus being quite beneficial to decreasing the brittleness level, making the brittleness level decrease from Level 4 to Level 1. Also, extremely high surface hardness and excellent wear resistance were obtained by aluminum-modified plasma nitriding due to the formation of hard phases of AlN and FeAl in the nitrided layer, with the surface hardness rising from 755 HV0.025 to 1251 HV0.025 and the wear rate reducing from 8.15 × 10−5 g·N−1·m−1 to 4.07 × 10−5 g·N−1·m−1. In other words, compared with traditional plasma nitriding, wear resistance was enhanced by two times after aluminum-modified plasma nitriding. Therefore, this study can provide comprehensive insights into the surface characteristics and combined performance of aluminum-modified plasma nitriding layers.

Characterizing sliding wear behavior of A1100/AlFe (p) composites produced via repeated fold-forging and annealing

Abstract Aluminum matrix/aluminum-iron intermetallic composite materials pose challenges in plastic processing due to the susceptibility of hard intermetallic compound particles to fracture. This study introduces a novel fabrication method involving pure iron mesh, hot-dip aluminum plating, and solidification. Through ten consecutive folding, forging, and intermediate annealing cycles, aluminum matrix and iron undergo diffusion, leading to the formation of Fe2Al5 and FeAl3 interface reaction layers, as confirmed by X-ray diffraction analysis. Subsequent forging cycles cause the breakage or detachment of Fe2Al5 and FeAl3 particles from the interface, resulting in the formation of large-sized Fe2Al5 and small-sized Fe2Al5 intermetallic particles. FeAl3 intermetallic particles are observed via microscopic examination. These particles can be uniformly dispersed within the aluminum matrix through plastic flow, enabling the successful fabrication of A1100/Fe2Al5 and AlFe3 composite sheets. Furthermore, the study investigates the impact of intermetallic compound content, sliding speed, and forward load on the dry sliding wear of A1100/FeAl composites. It is found that Fe2Al5 and AlFe3 intermetallic compound particles effectively mitigate adhesive wear, plowing, and oxidative wear of the composites. With an AlFe intermetallic compound content of 4.3 wt.%, the volume wear rate remains low under conditions corresponding to PV = 56.652 (equivalent to a normal load of 19.6 kPa and a sliding speed of 2.87 m s−1).

Microwave Absorbers Based on Fe and Fe–Al Particles Obtained in the Field of Rotational Magnetic Dipoles

Microwave Absorbers Based on Fe and Fe–Al Particles Obtained in the Field of Rotational Magnetic Dipoles

Absorbing materials based on magnetically controlled Fe-Al microparticles

Rotating permanent magnetic field (RPMF) method was used to obtain an absorbing material based on hexagonally packaged Fe-Al particles. A new kind of material - absorber in the microwave range was obtained. As the main characteristic, the reflection, absorption and attenuation spectra of the electromagnetic radiation of Fe-Al composites were obtained and analysed. Reflection characteristics of Fe-Al composite materials using the RPMF method were improved.

The Effect of Variation of Aluminum Thickness Series 7075 in Heat Treatment Solution on Tensile Strength and Microstructure

This research was conducted to examine the comparison of tensile strength and microstructure between two different aluminum heat treatments. This study aims to compare the microstructure and tensile strength of aluminum 7075 specimens after undergoing solution heat treatment at a temperature of 495°C with soaking time for 30 minutes and experiencing quenching cooling and those without solution heat treatment. The data collection process was carried out by conducting tensile testing and microstructural testing with two specimens each. The test results will be analyzed using tensile strength data and visual microstructure analysis. From the results of the analysis of tensile and microstructural test data, it can be concluded that only the 7075 aluminum specimen with a thickness of 1.4 mm shows the greatest decrease in tensile strength and spread of Mg-Zn and Fe-Al particles, when compared to specimen 7075 with a thickness of 0.6 mm which on the other hand, undergo the separation of Mg-Zn and Fe-Al particles. Meanwhile, the Al 7075 specimen with a thickness of 2.5 mm, the changes that occur only in the diffusion of Mg-Zn particles, which have a slight spread, appear a little faint.

Effects of Heat and Momentum Gain Differentiation during Gas Detonation Spraying of FeAl Powder Particles into the Water.

In this paper, dynamic interactions between the FeAl particles and the gaseous detonation stream during supersonic D-gun spraying (DGS) conditions into the water are discussed in detail. Analytical and numerical models for the prediction of momentum and complex heat exchange, that includes radiative effects of heat transfer between the FeAl particle and the D-gun barrel wall and phase transformations due to melting and evaporation of the FeAl phase, are analyzed. Phase transformations identified during the DGS process impose the limit of FeAl grain size, which is required to maintain a solid state of aggregation during a collision with the substrate material. The identification of the characteristic time values for particle acceleration in the supersonic gas detonation flux, their convective heating and heat diffusion enable to assess the aggregation state of FeAl particles sprayed into water under certain DGS conditions.

Experimental Study of a Townsend Discharge with a Multipoint Cathode on a Dynamic Platform Made of Magnetically Controlled Fe and Fe–Al Particles

Experimental Study of a Townsend Discharge with a Multipoint Cathode on a Dynamic Platform Made of Magnetically Controlled Fe and Fe–Al Particles

Molecular-Dynamics Study on the Impact Energy Release Characteristics of Fe-Al Energetic Jets.

Fe–Al energetic material releases a large amount of energy under impact loading; therefore, it can replace traditional materials and be used in new weapons. This paper introduces the macroscopic experiment and microscopic molecular-dynamics simulation research on the energy release characteristics of Fe–Al energetic jets under impact loading. A macroscopic dynamic energy acquisition test system was established to quantitatively obtain the composition of Fe–Al energetic jet reaction products. A momentum mirror impacting the Fe–Al particle molecular model was established and the microstructure evolution and impact thermodynamic response of Fe–Al particles under impact loading were analyzed. The mechanism of multi-scale shock-induced chemical reaction of Fe–Al energetic jets is discussed. The results show that the difference in velocity between Fe and Al atoms at the shock wave fronts is the cause of the shock-induced reaction; when the impact strength is low, the Al particles are disordered and amorphous, while the Fe particles remain in their original state and only the oxidation reaction of Al and a small amount intermetallic compound reaction occur. With the increase of impact strength, Al particles and Fe particles are completely disordered and amorphized in a high-temperature and high-pressure environment, fully mixed and penetrated. The temperature of the system rises rapidly, due to a violent thermite reaction, and the energy released by the jet shows an increasing trend; there is an impact intensity threshold, so that the jet release energy reaches the upper limit.

Environmentally friendly chemical synthesis of intermetallic iron aluminide submicrometer particles

Intermetallic iron aluminide (FeAl) in the submicrometer range is an emerging material for industrial applications due to its improved ductility and enhanced properties. In addition, preparing high-surface-area FeAl powder is highly desired due to its catalyst applications. The chemical synthesis of FeAl is feasible for mass production. However, previous synthesis methods require extensive use of toxic chemicals, organic solvents, and specialized environment-controlled facilities. To achieve a cleaner synthesis of FeAl powder with a high surface area, herein, we propose a new synthesis route. First, an Fe–Al oxide precursor, FeAl2O4, was prepared from iron and aluminum nitrates. Then, the oxide precursor was reduced to FeAl using CaH2 in molten LiCl at 600°C–700 °C. The reduction at 700 °C resulted in a single-phase intermetallic FeAl without any impurity phase, whereas at 600 °C and 650 °C, a trace of Al(OH)3 was detected under X-ray diffraction, indicating an incomplete reduction. N2 adsorption–desorption analyses and scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy confirmed the formation of submicrometer FeAl particles. The surface area of the prepared FeAl powder was as high as 88 m2/g, which is three times higher than that reported for Fe3Al nanoparticles prepared via a physical approach. We further performed a screening-level lifecycle assessment to evaluate the prospective environmental impact of the FeAl synthesis route. The cumulative energy demand and global warming potential associated with 1-kg-FeAl synthesis were 566 MJ and 41 kg CO2e, respectively, which are about half of those for existing LiAlH4-based methods. Therefore, the proposed synthesis route is promising for environmentally friendly synthesis of FeAl particles.

Экспериментальные исследования таунсендовского разряда с многоострийным катодом на динамической платформе из магнитоуправляемых частиц Fe и Fe-Al

Experimental results of the Townsend discharge in the air gap and atmospheric pressure from a multi-pin cathode based on a dynamic platform of magnetically controlled Fe and Fe-Al particles presented. Dynamic platform method formation from magnetically controlled particles for cathode surface presented. The current-voltage characteristics are obtained for various configurations of the cathode design (with a flat electrode without magnetically controlled particles, with a multi-pin cathode with magnetically controlled Fe or Fe-Al particles), as well as with the presence of a heated spiral in the electrode gap. The use of a multi-pin cathode based on the dynamic platform of magnetically controlled Fe and Fe-Al particles allows to maintain the average electric field strength in the discharge gap and to increase the spark discharge current.

Wettability control of modified stainless steel surfaces for oxide catalyst carrier slurry coating

Micrometer sized FeAl particles were added on 304 stainless steel surfaces to prepare rough surfaces with irregular patterns to make the surface super hydrophilic in order to effectively coat catalyst carrier alumina slurry on them. This method was compared with other conventional methods as follows. Micromachining and acid etching were firstly tried to prepare regular patterned surfaces with square micropillar arrays. Sand blasting was then tried to create micro roughness of the surface by removing materials from the surface. These methods were not so successful with contact angles higher than 50° for concentrated alumina slurry on the treated surfaces. In contrast to this, micrometer sized FeAl particles added 304 stainless steel surfaces showed excellent wettability with contact angles as low as 15° for concentrated alumina slurry on the treated surface. It was also observed that FeAl treated stainless steel surfaces were stable up to 700°C, indicating good adhesion between the catalyst support substrate and catalyst carrier layer at high temperatures.

Oxidation performance and degradation mechanism of the slurry aluminide coating deposited on Super304H in steam at 600–650 °C

A triple-layered slurry aluminide coating was prepared on Super304H, composed of Al-rich FeAl layer, Fe-rich FeAl layer and α-Fe(Cr, Al, Ni) interdiffusion layer dispersed with (Ni, Fe)Al particles from outer to inner. Oxidation and degradation process of the coating has been investigated at 600 °C~650 °C in steam, by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Results showed an extremely thin α-Al2O3 scale was formed on the coating. The microstructural degradation of the aluminide coating occurred due to phase transformation from FeAl to α-Fe and (Ni, Fe)Al particles near the interface between the FeAl layer and the interdiffusion zone. Related mechanisms were discussed.

An electro-Fenton system with magnetite coated stainless steel mesh as cathode

An electro-Fenton system with magnetite coated stainless steel (SUS) mesh as cathode was developed and tested for removing methylene blue in wastewater. For better adhesion between magnetite particles and SUS mesh surface, surface roughening of SUS mesh with FeAl particles was carried out. 850 °C was chosen as the optimized calcination temperature for FeAl treatment. When SUS meshes were coated with magnetite particles and applied as the cathode in an electro-Fenton system, catalytic activation of in situ produced H2O2 was enhanced. And this activation occurred heterogeneously on the surface of magnetite particles on cathode rather than homogeneously with free roaming leached ferrous ions. By coating magnetite particles on SUS meshes, degradation efficiency of methylene blue in neutral conditions was better than that in acidic conditions with bare SUS meshes as cathode in our electro-Fenton system.

The resistance of an aluminide coating on a high-strength ASTM A29 steel subjected to a temperature of 850 °C

An ASTM A29 steel was coated with aluminide by dipping in a molten Al bath at 700 °C for 16 s. The resistance of ASTM A29 steel to high-temperature oxidation drastically decreased upon oxidation at 850 °C for 12 h, whereas the oxidation resistance of the aluminised steel subjected to hot dipping was higher (by 25-fold). The external part of the aluminide layer, which consists of Fe2Al5, FeAl2, and FeAl(Cr, Si) phases scattered in the Fe2Al5 phase, was formed through the outward diffusion of Al and inward diffusion of Fe. The Fe2Al5 phase played an important role as a reservoir of Al atoms that form the alumina (Al2O3) scale, while Cr and Fe from the FeAl(Cr, Si) particles and accelerated the conversion of the metastable θ-Al2O3 phase to a stable α-Al2O3 phase. Consequently, the parabolic rate constants of aluminised steel decreased with extended oxidation time.

Evolution in microstructure and corrosion behavior of AlCoCrxFeNi high-entropy alloy coatings fabricated by laser cladding

AlCoCrxFeNi high-entropy alloys (HEAs) coatings were prepared on the surface of 45# steel by laser cladding with different contents of Cr (x = 0.50, 0.75, 1.00, 1.50, 2.00). A model was established to estimate the content of each component in the coatings, based on which three parameters including mixing entropy (△Smix), net driving factor (Ω) (Ω = Tm⋅△Smix/|△Hmix|Ω=Tm⋅Smix/|△Hmix|), and atomic size difference (δ) were calculated to precisely predict phase constituents in the coatings. The evolution in microstructure and corrosion behavior of the coatings with the change in x was investigated comprehensively. Results indicated that the dilution rate of the coatings was gradually increased with the increase in x. The coatings with x = 1.00 and 1.50 were composed of a single solid solution with the face-centered cubic (FCC) structure. A small number of fine equiaxial FeAl3 particles were also observed in the coatings with x = 0.50, 0.75, 2.00. Corrosion resistance of the coatings was improved first and then decreased with the increase in x in the electrochemical tests carried out in 0.1 mol L−1 HCl and 3.5 wt% NaCl solutions. The similar phenomenon was observed in the immersion tests. The optimum corrosion resistance was obtained in the coating with x = 1.50, in which the content of Cr reached the maximum value. Corrosion resistance of 45# steel could be considerably improved by laser cladding an AlCoCrxFeNi HEA coating on its surface.

CHARACTERISTICS OF Al-Fe SINTERS MADE BY THE POWDER METALLURGY ROUTE

The Al/Fe material was prepared by the powder metallurgy route with an additional intermediate stage which was a centrifuge of powder mixture. The application of the centrifuge stage was applied to obtain circular phase distribution of Al-rich phases in a sintered material. Iron powder with a particle size under 100 μm and aluminum powder with a particle size of about 25 μm, were used as starting materials. To determine the effect of centrifuging time on the distribution of Fe-Al particles, scanning electron microscopy (SEM, EDS) and XRD techniques were used. Microstructure observations show the influence of the centrifuging time on the distribution of Fe particles. It was observed that a longer centrifuging time caused changes in the ratio concentration of elements and allowed the growth of the intermetallic phase at the interface between solid Al and Fe particles.

Solidification Mechanism of the D-Gun Sprayed Fe-Al Particles

AbstractThe detonation gas spraying method is used to study solidification of the Fe-40Al particles after the D-gun spraying and settled on the water surface. The solidification is divided into two stages. First, the particle solid shell forms during the particle contact with the surrounding air / gas. Usually, the remaining liquid particle core is dispersed into many droplets of different diameter. A single Fe-Al particle is described as a body subjected to a rotation and finally to a centrifugal force leading to segregation of iron and aluminum. The mentioned liquid droplets are treated as some spheres rotated freely / chaotically inside the solid shell of the particle and also are subjected to the centrifugal force. The centrifugal force, and first of all, the impact of the particles onto the water surface promote a tendency for making punctures in the particles shell. The droplets try to desert / abandon the mother-particles through these punctures. Some experimental evidences for this phenomenon are delivered. It is concluded that the intensity of the mentioned phenomenon depends on a given droplet momentum. The droplets solidify rapidly during their settlement onto the water surface at the second stage of the process under consideration. A model for the solidification mechanism is delivered.

Effect of Fe-rich particles and solutes on the creep behaviour of 8xxx alloys

The creep behavior of 8xxx aluminum conductor alloys with different quantities of Fe-rich particles and solutes was investigated. Creep resistance was significantly improved with large amounts of Fe-rich particles and solutes. At 100 °C, a high Fe solute content (0.023 wt.%) had a stronger effect on creep resistance than FeAl3 particles. However, as the temperature increased to 150 and 200 °C, the effect of a high amount of FeAl3 particles (2.5 vol.%) was stronger. The threshold stress increased with increasing FeAl3 particle and Fe solute contents, with the effect of each factor being independent, but it decreased with increasing temperature. The true stress exponents were calculated to be 3.1, 3.8, and 4.5 at 100, 150 and 200 °C, respectively.

Dehydrogenation characteristics of LiAlH4 improved by in-situ formed catalysts

The hydrogen storage properties and catalytic mechanism of FeCl2-doped LiAlH4 were investigated in minute details. LiAlH4-2mol% FeCl2 samples start to release hydrogen at 76°C, which is 64°C lower than that of as-received LiAlH4. Isothermal desorption measurements show that the 2mol% FeCl2-doped sample releases 7.0wt% of hydrogen within 17min at 250°C. At lower temperatures of 110°C and 80°C, the sample can release 4.4wt% and 3wt% of hydrogen, respectively. The apparent activation energy of LiAlH4-2mol% FeCl2 samples for R2 is 105.02kJ/mol, which is 67kJ/mol lower than that of pure LiAlH4. The reaction between LiAlH4 and FeCl2 during ball milling was found by analyzing the X-ray diffraction results, and Fe-Al particles formed in-situ from the reaction act as the real catalyst for the dehydrogenation of LiAlH4.

Comparison of corrosion behavior of Al‐Mn and Al‐Mg alloys in chloride aqueous solution

The microstructure and corrosion behavior of Al‐Mn alloy 3A21 and Al‐Mg alloy 5A05 in 3.5% NaCl solution were examined and compared. The results of the microstructure survey performed by optical microscope confirm the inhomogeneous nature of the intermetallic particles of the two alloys. The X‐ray diffraction (XRD) analysis reveals the presence of intermetallic Al6Mn and Al6(FeMn) particles in the 3A21 alloy and Al3Mg2, Mg2Si and FeAl3 particles in the 5A05 alloy, respectively. Electrochemical results, in parallel with corrosion morphology characterization, show that these two alloys both suffer pitting corrosion type attack under the conditions employed in the present study, with better corrosion resistance and stronger repassivating capability for the 5A05 alloy. Furthermore, the validity of the difference ΔE (Epit–Ecorr, Ecorr–Eprot) and Eptp as criteria for susceptibility to localized corrosion of aluminum alloys are also discussed.