Al3Fe Particles Research Articles

Preparation of low-cost, high-strength and fast-dissolving (MgO–Al3Fe)/AZ91 magnesium matrix composites using a novel in-situ reaction

In this work, an in-situ MgO–Al3Fe particles reinforced magnesium matrix composite has been successfully prepared through a novel reaction between the AZ91 alloy and Fe3O4 precursor. The results show that the micron-sized spheroidal MgO and polygonal Al3Fe particles not only significantly refine the grains of the Mg matrix but also lead to a decrease in the number and size of β-Mg17Al12 phases. Furthermore, the in-situ MgO–Al3Fe particles have also significantly increased the volume fraction of dynamic recrystallization in the as-extruded composite. Compared to the AZ91 alloy, the strength and ductility of the as-extruded composite have been synergistically improved, with a yield strength, ultimate tensile strength, and elongation of ∼415.4 MPa, ∼480.1 MPa, and ∼5.9 %, respectively. Meanwhile, the dissolution rate of the as-extruded composite has significantly increased by about 1700 % relative to the AZ91 alloy.

Effect of the Reinforcing Particle Introduction Method on the Tribomechanical Properties of Sintered Al-Sn-Fe Alloys

The present paper reports the results of the comparative study of mechanical properties of sintered disperse-strengthened Al–40Sn alloy depending on the method of reinforcing particle introduction. The study is performed on two mixtures of aluminum and tin powders: one is admixed with 5.5–14.6 wt% of pure iron powder and the other contains the same amount of iron, but as a component of aluminide Al3Fe powders. The volume fraction of tin remains unchanged in all mixtures, being equal to 20%, and the concentration of hard particles increases due to a decrease in the volume fraction of the aluminum phase. Green compacts are sintered in the vacuum furnace at a temperature above the melting point of aluminum. The sintered material is a composite containing three phases: α-Al, β-Sn, and Al3Fe, in which the tin volume fraction is constant. Testing of the sintered composites for compression shows that the addition of finished Al3Fe particles has a more beneficial effect on their mechanical properties as compared to the addition of pure iron powders. In the latter case, aluminides are formed during sintering. The ultimate strength of composites reaches 180 MPa. Mechanisms of sintering of composites and the related structure and mechanical properties are discussed.

Design of Al based composites reinforced with in–situ Al2O3, AlB2 and Al13Fe4 particles

Al based composites reinforced with γ–Al2O3, AlB2 and Al13Fe4 particles were synthesized via sintering the Al–2.5Fe2O3–7.5B2O3, Al–5Fe2O3–5B2O3 and Al–7.5Fe2O3–2.5B2O3 systems and hot extruding. The in–situ formed γ–Al2O3 nanoparticles mainly distribute along grain boundaries, while micron AlB2 and Al13Fe4 particles disperse within matrix grains. All of the composites form fiber texture in the longitudinal section, with the average grain size less than 1 μm. The composite synthesized from Al–2.5Fe2O3–7.5B2O3 has the best ultimate tensile strength at a series of temperatures, which can be 460 MPa and 208 MPa at 250 °C and 400 °C, respectively. It is deduced that the strengthening effect of Al13Fe4 particles is weaker than Al2O3 and AlB2, and the composite of Al–xFe2O3–yB2O3 is supposed promising for application at elevated temperatures.

Effect of Homogenization and Precipitation Heat Treatments on Localized Corrosion of Al-Mn-Zr Alloy with Fe Impurity

This study aimed to enhance the corrosion resistance of an Al-Mn-Zr alloy containing Fe impurities by using heat-treatment processes. Three processes were implemented to distribute intermetallic particles uniformly, promote Al6(Mn, Fe) and Al3Zr particle formation, and eliminate Fe and Zr segregation. Increasing the amount of Al6(Mn, Fe) reduced the galvanic effect between the Al matrix and Al3Fe particles, leading to improved localized corrosion resistance. Al3Zr promoted smaller grain size by preventing recrystallization. Microstructure analysis confirmed the inhibitory effect on grain growth and the promotion of Al6(Mn, Fe) and Al3Zr particle formation. The effect of grain size on galvanic corrosion was evaluated through corrosion simulation. Furthermore, the improved localized corrosion resistance was evaluated through electrochemical and immersion tests. Consequently, the designed heat-treatment process significantly improved the localized corrosion resistance of the Al-Mn-Zr alloy with Fe impurities. These results demonstrate the effectiveness of the used heat-treatment processes in improving the corrosion resistance of the alloy.

Aluminum Alloy Anode with Various Iron Content Influencing the Performance of Aluminum-Ion Batteries.

Considerable research has been devoted to the development of cathode materials for Al-ion batteries, but challenges remain regarding the behavior of aluminum anodes. Inert oxide (Al2O3) film on Al surfaces presents a barrier to electrochemical activity. The structure of the oxide film needs to be weakened to facilitate ion transfer during electrochemical activity. This study addresses oxide film challenges by studying Al alloy anodes with different iron content. The results reveal that using an anode of 99% Al 1% Fe in a cell increases the cycling lifetime by 48%, compared to a 99.99% Al anode. The improvement observed with the 99% Al 1% Fe anode is attributed to its fractional surface area corrosion being about 12% larger than that of a 99.99% Al anode. This is coupled to precipitation of a higher number of Al3Fe particles, which are evenly scattered in the Al matrix of 99% Al 1% Fe. These Al3Fe particles constitute weak spots in the oxide film for the electrolyte to attack, and access to fresh Al. The addition of iron to an Al anode thus offers a cheap and easy route for targeting the oxide passivating film challenge in Al-ion batteries.

In-situ synchrotron X-ray radiography study of primary Fe-rich phases growth in Al-Fe( Cu) alloys

Plate-like iron-rich intermetallic phases (Fe-rich phases) greatly decrease the elongation and fatigue strength of recycled Al alloys. The alloy composition and the manufacturing process parameters influence the type, and shape of Fe-rich phases. In this study, the influence of the cooling rate (0.1, 0.5, and 1.0 °C/s) on the nucleation and growth of primary Fe-rich phases during solidification of Al-Fe(Cu) alloy has been quantified by synchrotron X-ray radiography. The Kikuchi patterns and deep-etched methods showed that rod-shape and plate-like primary Al3Fe phases are present in the studied alloy. The in-situ experimental results indicate that the total number and number density of primary Fe-rich phases in AlFe alloys is very similar at cooling rates of 0.1 °C/s and 1.0 °C/s but increases a 300 % at cooling rate of 0.5 °C/s. The nucleation rate of Al3Fe in AlFe alloys at three cooling rates (0.1, 0.5, and 1.0 °C/s) are 15.5, 44.0, 25.0 No./s, respectively. These decrements are due to alloy compositions are very closed to the eutectic composition (about 1.8% Fe), the less time for them to form primary Fe-rich phases at high cooling rate of 1.0 °C/s. The variation trend of total number, number density, and nucleation rate of primary Al3Fe phases in Al-Cu-Fe alloys is similar to those of in AlFe alloys. The maximum length of typical Al3Fe phases in AlFe alloys decrease from 845 μm to 222 μm as the cooling rate increased. This is because that higher cooling rate resulting in less diffusion time for limiting Fe atoms diffusion, also inhibiting them grow into large plates. The combined Cu addition and higher cooling rate resulting in the constitutional undercooling, and finally promote the formation of refined primary Al3Fe particles.

MECHANICAL PROPERTIES OF SINTERED AL-SN-FE ALLOYS

Plastic flow under compression was studied in samples of Al-Sn-Fe alloys produced by sintering from elemental powder mixtures. Some of the sintered composites were additionally compacted at 250°C in a closed mold at a pressure of 300 MPa, and some were processed via equal-channel angular pressing using route A (ECAP-A) at the same temperature. A key structural feature of the sintered alloys is the presence of agglomerates of solid Al3Fe particles cemented with tin, formed in place of iron powder particles as a result of interaction between Al and Fe during sintering. The agglomerates have high strength but are sufficiently ductile owing to tin. They do not break during deformation and effectively suppress the propagation of localized flow bands and microcracks. In compression tests of three-phase Al-20Sn-17Al3Fe composite samples, the particle agglomerates retained their shape and moved as solid structures, while the samples showed good ductility during testing. In ECAP processing via route A, the agglomerates were pulled in the direction of material flow, which negatively affected their ductility in subsequent compression tests.

True fracture stress of UFG samples of Al 6101 alloy

This paper presents the results of studies on the true fracture stresses of the Al alloy 6101 with an ultrafine-grained (UFG) structure processed by equal channel angular pressing — conform (ECAP-C) method and the same alloy after artificial aging (AA state). The grain size in the UFG state was about 500 nm. Aging particles and Al3Fe particles were present in the structure of AA and UFG state. Strength and yield stress increase as a result of the formation of UFG structure. The true strain to failure in AA and UFG states of 6101 alloy, taking into account the measurement error, is the same. In this case, the true fracture stress of samples with the UFG structure is markedly higher than the true fracture stress of samples with the AA structure. An explanation for the increase in the true fracture stress of specimens with UFG structure based on a generalization of the Hall-Petch relation and the Zener-Strauss model, a criterion of pore formation on the particle, is proposed.

Microstructural Refinement of As-Cast Al–Mg Alloy by Ultrasonic Melt Treatment Using a Titanium Sonotrode under Fully Liquid Condition

The effects of ultrasonic treatment (UST) using a titanium (Ti) sonotrode in a fully liquid stage on the grain refinement and mechanical properties of as-cast Al–Mg alloy billets were investigated. To clarify the grain refinement mechanism, the grain size (GS) and dendrite arm spacing (DAS) were examined as functions of the growth restriction factor (Q) dependent on the Ti dissolution from the sonotrode, and compared to those in the as-cast and re-melted states of the samples inoculated using an Al–10 mass%Ti master alloy. In addition, the formation and dissolution behavior of Al3Ti intermetallic particles acting as a heterogeneous nuclei was indirectly observed by measuring the electrical resistivity during isochronal annealing. In comparison with the chemical refiner inoculation, the UST effectively refined not only the GS but also the DAS, both of which showed similar slightly concave upward curves with an increasing slope against 1/Q. Electrical resistivity measurement results provided indirect evidence that the dissolved Ti was present as a solute during the solidification stage. The GS, DAS, and electrical resistivity results all suggest that the dissolved Ti refined the GS primarily by solute-induced growth restriction effect rather than by providing heterogeneous nucleation sites. The UST effect on the microstructure refinement was efficient when the Ti-dissolution content was as low as less than 0.05 mass%. The refinement of grains, Al3Fe particles, dendrites, and pores by the UST significantly improved mechanical properties, especially the elongation at break.

Design and fabrication of a (6.4γ–Al2O3 + 18Al13Fe4)/Al (wt.%) composite utilizing fine grain strengthening and dispersion strengthening at elevated temperatures

In this work, a (6.4γ–Al2O3 + 18Al13Fe4)/Al (wt.%) composite (AFO) was in-situ synthesized through the chemical reaction between Al and oxide powders. After hot extrusion, the formed nanometric γ–Al2O3 particles exhibit networks, locating along matrix grain boundaries. The submicron Al13Fe4 particles have similar size with the α–Al grains and disperse uniformly among the matrix. It is supposed that the γ–Al2O3 particles are efficient for grain boundaries stabilization at elevated temperatures, while the Al13Fe4 particles generate further dispersion strengthening effect. As a result, the AFO composite exhibits attractive high-temperature intensity and heat stability. The yield strength of tensile test at 300 °C is 270 ± 6 MPa, while it can still remain to be 119 ± 10 MPa at 500 °C. It is regarded that this work may provide new insights for designing new Al based composites for elevated temperature applications.

Metallurgical investigation of aluminum anode behavior in water-in-salt electrolyte for aqueous aluminum batteries

Although ionic liquid electrolytes (ILs) are environmentally unfriendly, they are the most common electrolyte used in aluminum-ion batteries (AIB). Aqueous electrolytes offer a more sustainable alternative, but problem with oxide passivating barrier on Al surface becomes more profound. Recently, a new sub-class of aqueous electrolytes, water-in-salt (WIS) of (AlCl3·6H2O), has been considered, but experimental validation of the behavior of the Al electrode over cycling is required. This work investigates aluminum/graphitic cells using WIS electrolytes with a mass ratio of salt to water of 4, 8, and 12 and finds that they show similar trends in cycling performance. The degradation observed over cycling has been attributed to the formation of a detrimental solid electrolyte interphase (SEI) layer on the Al surface. It was found that WIS 4 increased Al corrosion, resulting in a slightly higher capacity and longer cycling life. Metallurgical observation showed that the Al matrix has a tendency to initiate corrosion around Al3Fe intermetallic phases in both WIS and ILs. This implies that the presence of Al3Fe particles allows the electrolyte to break the oxide barrier and access the bulk Al. These results suggests that metallurgical treatments are important to enhance the electrochemical performance of AIB.

Microstructure and mechanical property evolution of additive manufactured eutectic Al-2Fe alloy during solidification and aging

This study presents the microstructure and mechanical properties of an additive manufactured recyclable Al-2Fe alloy fabricated by laser powder bed fusion (LPBF). The microstructure evolution of the Al-2Fe alloy aged at elevated temperatures and its impact on the mechanical properties were systematically investigated. Firstly, the single melt scanning experiment verified that Al-Al6Fe anomalous eutectic structure was initially formed from the liquid phase. Secondly, the as-built Al-2Fe contains nano-size and rod-shaped Al6Fe particles which uniformly dispersed in a supersaturated Al matrix. The Al6Fe particles with an average diameter of ~89 nm shows a coherent crystallographic relationship with the matrix as (046)Al6Fe // (2¯02¯)Al, and [032¯]Al6Fe // [1¯11]Al. The ultimate tensile strength and total elongation of 287.0 MPa and 12.0% were obtained in the ultrafine as-built Al-2Fe, respectively. Aging at elevated temperatures made the Al6Fe particles coarsened and transformed into Al13Fe4 particles at 350 °C. The amount of the total Al-Fe intermetallic compounds (Al6Fe+Al13Fe4) increased with the aging temperature due to the precipitation of the supersaturated Fe atoms. It exhibits a slow increase in grain size and a decrease in dislocation density in the Al-2Fe samples with the increase of aging temperature. All Al6Fe particles were transformed into coarse Al13Fe4 particles at 550 °C. Thirdly, the quantitative analysis indicates that the dominant contribution to the yield strength derives from the dispersion strengthening mechanism by creation of fine Al6Fe and Al13Fe4 particles. The results in this work demonstrate that ultrafine microstructure can be obtained in a simple binary Al-Fe alloy as a result of the extremely high cooling rate during LPBF process, which offers a design strategy towards high-strength recyclable aluminum alloys.

Mechanical and Tribological Properties of Sintered Aluminum Matrix Al–Sn Composites Reinforced with Al3Fe Particles

Mechanical and Tribological Properties of Sintered Aluminum Matrix Al–Sn Composites Reinforced with Al3Fe Particles

Structure refinement, mechanical properties and feasibility of deformation of hypereutectic Al–Fe–Zr and Al–Ni–Zr alloys subjected to ultrasonic melt processing

Hypereutectic Al–Fe and Al–Ni alloys offer a potentially attractive combination of properties, e.g. high-temperature strength and stability, high elastic modulus and low coefficient of thermal expansion. This potential, however, cannot be reached unless the structure of these alloys is refined so that their processing becomes possible. In this study, we for the first time apply ultrasonic melt processing for refining the structure of hypereutectic Al-4% Fe and Al-8% Ni alloys with 0.3 wt% Zr addition. Both primary Al3Fe and Al3Ni particles as well as aluminum/eutectic grains are significantly refined. It is suggested that cavitation-induced fragmentation of primary Al3Zr crystals plays a significant role in the nucleation of intermetallics as well as aluminum. Furthermore, the hardness and tensile properties of the alloys substantially increase after ultrasonic treatment due to the refined structure, which also contributes to the considerably enhanced ductility of the alloys. As a result, the fracture mode changes from brittle fracture to ductile fracture. The increase in ductility makes the alloys suitable for hot deformation, which is demonstrated by lab-scale hot rolling. In addition, precipitation hardening of the alloys can be achieved by high-temperature annealing at 450 °C due to retained Zr in the Al solid solution upon solidification. The results are supported by the analysis of the composition of a supersaturated solid solution of Zr in Al and scanning and transmission electron microscopy that confirms the precipitation of coherent Al3Zr nanoparticles. It is demonstrated that a combination of ultrasonic melt processing and alloying with Zr makes it feasible to develop new class of hypereutectic casting and wrought alloys based on the Al–Fe and Al–Ni systems.

Microstructure, tensile and wear properties of a novel graded Al matrix composite prepared by direct energy deposition

A novel graded Al matrix composite (AMC) was prepared by direct energy deposition (DED) from the mixture of pure Al, Cr and Fe powders. From the perspective of a single molten pool, the microstructure consists of two regions: AMC region with coarse Al13Fe4 laths and AMC region with fine Al13Fe4 particles. With increasing the deposited layer, the content of coarse Al13Fe4 lath decreases and the content of fine Al13Fe4 particle increases, which indicates the formation of a graded structure. Interestingly, the samples cut from different positions of graded AMC deposit exhibit the identical ultimate tensile strength (UTS, ∼222 MPa) except that the top region presents the higher ductility (3.8%) than the bottom region (1.1%). However, the bottom region presents the higher hardness (84.12 HV) and the better wear resistance than the top region. Moreover, this novel Al matrix composite prepared by DED exhibits favorable wear resistance compared to conventional cast Al-12Si alloy. This novel grade Al matrix composite possesses multifunctional properties of wear and tensile, which can be used as structural and anti-wear component in aerospace and automotive field.

The influence of iron impurities on the compression behaviour of Al-2.24Mg-2.09Li alloy

As a major impurity element in aluminium-lithium (Al-Li) alloys, iron (Fe) reduces formability, fracture toughness, and fatigue resistance by solidifying into Al6Fe and Al3Fe particles. The research was performed in order to estimate the influence of Fe impurities on the compression behaviour of Al-2.24Mg-2.09Li alloy. The investigation was performed on the samples in as cast and solution hardened condition. The solution hardening was applied to improve the mechanical properties by dissolving intermetallic particles and enriching ?Al matrix with Mg. However, the higher strength properties and temperature increase during the compression testing were observed in as cast condition. Microstructural investigation revealed significant differences in microstructure changes between the samples in as cast and solution hardened condition. In as cast sample the barrelling effect led to the unequal deformation and surface texture development. The eutectic Al3Fe particles located in the ?Al interdendritic areas did not significantly impact microstructure changes. Although the solution hardening led to enrichment of ?Al matrix with Mg and Fe, the Al3Fe particles were not dissolved. The coarse morphology of Al3Fe particles and location at the grain boundaries of ?Al grains contributed to low energy intergranular fracture. The fracture nucleation and propagation across the grain boundaries resulted in lower strength values.

Double Reinforcement of Al–Fe Intermetallic Composites Fabricated by Friction Stir Processing

A double reinforced layer on an aluminum alloy surface was produced using friction stir processing (FSP) by adding 34CrNiMo6 powder into Al (AA2024) substrate for better wear resistance and gradient transitions. The microstructures of the composites were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The phase composition was examined by X-ray diffraction (XRD). The results show that the double reinforced layer of the Al13Fe4 intermetallic compound could be successfully fabricated via FSP. The volume fraction of Al13Fe4 in the double reinforced layer was higher than in the single reinforced layer due to adding 34CrNiMo6 powder and reinforced twice, and the Al13Fe4 particles were dispersed more homogeneously in the double reinforced layer. The interfaces between the double and single reinforced layer had a good metallurgical bond. The microhardness of the double reinforcement layer was significantly increased. Compared with the AA2024 substrate, the microhardness of the double and single reinforced layers increased five- (576 HV) and two-fold (254 HV), respectively.

Effect of multi-pass friction stir processing on the microstructure and hardness of AA1100/Al13Fe4 in situ composites

In situ Al–Al13Fe4 surface composites were synthesized via friction stir processing (FSP) at aluminium plate with the addition of Fe2O3 particles and the effect of multi-pass of the FSP on microstructure and hardness was investigated. The defect free surface composites which consisted of a fine grained aluminium matrix (2–10 μm), Al13Fe4 particles (>250 nm and <100 nm) as well as some unreacted elemental iron and iron oxide fragments, were successfully produced. Compared with the base metal and the FSPed samples without particles addition, an improvement in hardness (up to 300%) was achieved in the surface composites. Also, a significant grain refining was detected.

Effect of friction stir processing on microstructure and tensile behavior of AA6061/Al3Fe cast aluminum matrix composites

Friction stir processing (FSP) has emerged as an effective secondary processing technique to improve the microstructure and properties of aluminum matrix composites (AMCs). Al/(0–15 wt%) Al3Fe AMCs were prepared by adding pure iron powder to molten aluminum and subjected to FSP. The microstructural changes before and after FSP were studied using OM, SEM, EBSD and TEM. Cast composites exhibited coarse grains, segregation, pores and sharp-edged particles. The distribution of particles was rearranged into a homogeneous distribution after FSP. Casting defects such as pores were eliminated. The sharp edges of Al3Fe particles were removed and rounded into near spherical shape. The grain size reduced remarkably due to severe plastic deformation and the pinning effect of reinforced particles. The density of dislocations increased considerably after FSP. The microstructural changes resulted in an improvement of tensile strength and ductility. The possible strengthening mechanisms were reported.

Effect of Si and Zr on the Microstructure and Properties of Al-Fe-Si-Zr Alloys

The effects of Si and Zr on the microstructure, microhardness and electrical conductivity of Al-Fe-Si-Zr alloys were studied. An increase in the Zr content over 0.3 wt. % leads to the formation of primary Al3Zr inclusions and also decreases mechanical properties. Therefore, the Zr content should not be more than 0.3 wt. %, although the smaller content is insufficient for the strengthening by the secondary Al3Zr precipitates. The present results indicate that high content of Si significantly affects the hardness and electrical conductivity of the investigated alloys. However, the absence of Si led to the formation of harmful needle-shaped Al3Fe particles in the microstructure of the investigated alloys after annealing. Therefore, the optimum amount of Si was 0.25–0.50 wt. % due to the formation of the Al8Fe2Si phase with the preferable platelet morphology. The maximum microhardness and strengthening effects in Al-1% Fe-0.25% Si-0.3% Zr were observed after annealing at 400–450 °C due to the formation of nanosized coherent Al3Zr (L12) dispersoids. The effect of the increasing of the electrical conductivity can be explained by the decomposition of the solid solution. Thus, Al-1% Fe-0.25% Si-0.3% Zr alloy annealed at 450 °C has been studied in detail as the most attractive with respect to the special focus on transmission line applications.