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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. [ABSTRACT FROM AUTHOR]

Replacing automotive components made of iron alloys with aluminum alloys is one of the strategies to reduce vehicle weight and increase fuel efficiency in the automotive sector. Semisolid casting is a metalworking process that combines casting and forming processes. In this process, the raw material being processed is in a mixture of liquid and solid phases, and the processing method uses a casting or forming method. This research aims to study the influence of mechanical agitation models on the aluminum alloy ADC12 to microstructure and mechanical properties. By using a metal mold, gravity casting has been used as the research methodology. Mechanical stirrers (round rod stirrers, straight plate stirrers, and twist plate stirrers) have been used to mix the aluminum ADC12 slurry for 60 seconds at a speed of 300 rpm. Additionally, the ADC12 aluminum slurry has been poured into a metal mold at a temperature of 600 °C. Optical microscopy, Scanning Electron Microscopy (SEM), secondary α-Al phase dendritic arm spacing, and Si eutectic phase have been used to observe directly the microstructure features. The hardness and the tensile tests have been used to examine the mechanical properties. ADC12 aluminum alloy with mechanical characteristics of 89.7 HB, tensile strength of 249.96 MPa, and strain of 4.33 percent have been produced by using the straight plate stirrer. A lower particle size value (31.6 mm) and a Shape Factor (SF) of 0.56 corroborate this mechanical quality. More research can be done on various types of aluminum alloys, higher stirring rotation speeds, and the size, quantity, and spacing of stir blades. [ABSTRACT FROM AUTHOR]

Secondary aluminum alloys in automotive industry have been rising in last decades; however, the iron content is still a concern whether recycled or high iron containing aluminum alloys can fulfill the mechanical requirements. As the proportion of recycled scrap increases in aluminum alloy components, the mixing and accumulation of impurities become significant issues. In this study, manganese was used to counteract the detrimental effects of iron. Accordingly, A356 alloy automobile wheels containing 0.002 wt%, 0.040 wt%, 0.069 wt%, and 0.14 wt% Mn were cast using the low-pressure die casting method, followed by T6 heat treatment. Optical microscope (OM) examinations were performed to observe intermetallics. Additionally, the mechanical properties of the produced wheels were evaluated through hardness measurements, tensile, and Charpy impact tests. After the Charpy impact test, fractured surfaces were examined using scanning electron microscopy (SEM). Micrographs from SEM and OM were quantified using digital image processing. To interpret this extensive dataset, a statistical model was developed using microstructural data as input through multiple linear regression analysis and analysis of variance. The results were discussed together with the sensitivity analysis. A weak negative linear correlation between Mn concentration and mechanical properties was found, indicating that Mn addition is not the primary factor for the observed decrease in mechanical properties. Elongation and yield strength were significantly influenced by both aspect ratio and particles/mm2, with greater sensitivity to particles/mm2. Additionally, impact energy was strongly affected by aspect ratio of particles (intermetallics and eutectic Si) and their concentration per unit area. [ABSTRACT FROM AUTHOR]

During the solidification of aluminum alloys with high iron concentrations in conjunction with electromagnetic stirring, the electromagnetic force induces movement of precipitated intermetallic grains containing iron. This force is assumed to cause macrosegregation of such compounds, although the movement process is complex due to the additional effects of melt flow on growth kinetics. The present work used in situ X-ray imaging to obtain insights into the macrosegregation process induced by electromagnetic stirring. This imaging was employed to observe the evolution of primary intermetallic α-Al(FeMn)Si grains during the solidification of an Al-10Si-2Fe-2Mn alloy in the presence of a rotating magnetic field. The α-Al(FeMn)Si grains were found to be uniformly distributed in the horizontal direction of the alloy without electromagnetic stirring but tended to congregate at the periphery of the specimen with stirring. In situ X-ray imaging confirmed that electromagnetic stirring also promoted growth of α-Al(FeMn)Si phase grains from the periphery into the center of the alloy. The α-Al(FeMn)Si phase at the sample periphery comprised a single grain, indicating that stirring led to dendrite growth. These observations together with ex situ crystallographic analyses demonstrated that macrosegregation in an Al-10Si-2Fe-2Mn alloy solidified with electromagnetic stirring resulted from grain coarsening of the α-Al(FeMn)Si phase at the sample periphery. • An X-ray imaging setup was developed to observe solidification sequences during electromagnetic stirring. • The evolution of the α-Al(FeMn)Si phase in the presence of electromagnetic stirring was observed. • The orientation of the α-Al(FeMn)Si phase was determined by the electron backscatter diffraction method. • Electromagnetic stirring promoted the grain growth of the α-Al(FeMn)Si phase. • Grain coarsening of the α-Al(FeMn)Si phase led to macrosegregation. [ABSTRACT FROM AUTHOR]

Iron aluminides are iron-aluminum alloys that have excellent resistance to oxidation at high temperatures with low density, high resistance/weight ratio and a low manufacturing cost. Due to its characteristics, these alloys are presented as an option to replace stainless steels in certain applications. This works intends report the casting process and subsequent analyses involving microstructure, mechanical properties, and corrosion resistance of two Fe-Al-C alloys (Fe-11wt%Al and Fe-25wt%Al, containing 0.31-0.37%C), which were prepared in an induction furnace and poured in a permanent mold. Samples of these alloys were characterized and presented elevated hardness values of 37 HRC (alloy Fe-11wt%Al) and 49.6HRC (alloy Fe-25wt%Al) and microstructure with aluminides type Fe3Al and FeAl and also carbides type K. The Fe-11wt%Al alloy exhibited superior resistance to uniform corrosion, although both Fe-Al-C alloys exhibited significantly higher corrosion rates compared to a binary iron aluminide in 0.5M H2SO4 containing naturally dissolved oxygen. [ABSTRACT FROM AUTHOR]

The paper considers the effect of introducing ferroalloys containing titanium and zirconium on the structure and heat-resistance of low-carbon ferroalloys. Theoretically and experimentally, it has been proven that the addition of 1.0 wt % of titanium and 0.1 wt % of zirconium to a low-carbon iron-aluminum melt containing 12–14 wt % of aluminum grinds its structure increasing tensile strength and refractory properties. Titanium and zirconium are strong carbide-forming elements. When introduced into a low-carbon iron-aluminum alloy, they form a large number of crystallization centers, thus, affecting its microstructure, allowing to get finer and more uniform granularity compared to an alloy without additive. This in turn increases the strength limit of processed alloy. In addition, the use of titanium as a modifying additive in a low-carbon ferroalloy allows increasing its heat-resistance, which exceeds several times the heat-resistance of famous chrome-nickel steel of Fe20Cr23Ni18 grade. As a result, a new technology for obtaining titanium and zirconium was developed based on research of the effect of their modifying additives on the structure and heat-resistance of low-carbon iron-aluminum alloys. [ABSTRACT FROM AUTHOR]

Abstract The creep behavior of a fully lamellar FeAl/FeAl 2 eutectoid alloy was shown to exhibit a minimum creep rate and the absence of a pronounced steady state regime. To reveal the underlying mechanisms of creep leading to the macroscopic response described above, comprehensive TEM investigation of several crept specimens were performed. In the early stages of creep, the FeAl phase primarily carries creep deformation by dislocation motion, whereas FeAl 2 remains mostly plastically undeformed, except in certain locations near colony boundaries where the lamellar structure is disrupted/absent. Within the colonies, where the lamellae are intact, deformation is accommodated at the FeAl/FeAl 2 interface, resulting in an increase in interface dislocations. This continues to be the case at the minimum creep rate. With further progression in creep, FeAl 2 begins to participate in the process of plastic deformation in a more substantive manner through twinning and slip, while FeAl continues to plastically deform and dynamically recover. Further beyond the minimum, the lamellar structure adjacent to the colony boundaries breaks down, and these areas become the primary contributors to creep and results in a continuous loss in creep resistance. Based on these observations in the fully lamellar material, the creep response of off-eutectoid Fe-58Al and Fe-62Al as well as single-phase FeAl 2 are explained. Highlights • Creep mechanism in a lamellar FeAl/FeAl 2 alloy is examined by electron microscopy. • Initially, FeAl deforms by slip and interface dislocation content increases. • A creep rate minimum then occurs and is associated with slip and twinning in FeAl 2. • Twins nucleate at the FeAl/FeAl 2 interfaces and FeAl 2 twins on the (001) plane. • Increase in creep rate at longer time results from lamellar structure breakdown. [ABSTRACT FROM AUTHOR]

Abstract Solid loading as a key parameter in gel casting influence both rheological behavior and stability of slurry. It also has strong impacts on microstructure and final properties of porous FeAl intermetallics. In this study, a designed non-aqueous gel casting has been developed for fabrication of porous FeAl intermetallics. The SEM analysis, bubble point method and compression test were used to investigate pore structure and properties of porous FeAl intermetallics. Results reveal that higher solid loading will improve the uniformity of pore structure and lead a decrease in maximum pore size. Gas permeability decreases but compressive strength increases with increasing solid loading. The quantitative relationship between maximum pore size (d m) and solid loading (φ) is d m = 10.52 − 0.15 φ (35 ≤ φ ≤ 50); the relationship between gas permeability (K) and solid loading (φ) is K = 13.99 − 0.22 φ (35 ≤ φ ≤ 50). Further, the distinctive phase transformation and pore formation mechanism are the main reasons for tiny volume expansion and highly open porosity of final products, respectively. Altogether, this work provides a strategy to fabricate porous FeAl intermetallics with adjustable pore structure and properties by controlling the solid loading, suggesting that the non-aqueous gel casting is a promising candidate for the preparation of porous FeAl intermetallics. Graphical abstract Unlabelled Image Highlights • Porous FeAl intermetallics were fabricated using a non-aqueous gel casting. • Higher solid loading can improve the uniformity of pore structure. • Maximum pore size and gas permeability decrease with increasing solid loading. • Compressive strength increases with increasing solid loading. • Pores are formed by removal of gel network and phase transformation. [ABSTRACT FROM AUTHOR]

Abstract The nanocrystalline Fe 60 Al 35 Sn 5 alloy was produced from elemental powders in a high-energy ball mill. A full microstructural analysis and morphologic characterization of powder samples were performed by X-ray diffraction experiments and scanning electron microscopy as a function of milling time (0–60 h). The microstructure analysis of the microstructure of milled powders is focused on the evolution of the grain size, lattice strain and dislocations density. Experimental results demonstrated that a bcc-Fe (Al, Sn) solid solution with a mean crystallite size about 16 nm was achieved. In addition, the thermal behavior of the milled powders was examined by differential scanning calorimetry. Highlights • Analysis of the influence of minor Sn addition to Fe-Al nanocrystalline alloy produced by ball milling. • The single phase of bcc-Fe (Al, Sn) was totally formed after 20 h. • At low milling times the coexistence of Fe and Fe-rich solid solution was found. [ABSTRACT FROM AUTHOR]

In this paper, Fe3Al-based alloy with a designed 30 at% Al content is fabricated using an innovative wire-arc additive manufacturing process. In order to investigate the influences of postproduction heat treatments on the additively manufactured alloy, three postproduction heat treatment methods were applied to the as-fabricated material. The morphologies, phase constituents, and mechanical properties of samples produced by the different heat treatments were characterized and analyzed in detail. According to the results, the applied heat treatments can considerably change the microstructure and mechanical properties of the as-fabricated Fe3Al-based alloy. Also, the hardness and tensile properties of Fe3Al-based alloy are found relevant to the Al-rich precipitates observed in the morphologies, which are generated by the additional thermal processes on the homogenized Fe3Al-based alloy. [ABSTRACT FROM AUTHOR]

In this work, the evolution of microstructure and mechanical properties of FeAlCrV and FeAlCrMo medium-entropy alloys were studied. In both FeAlCrV and FeAlCrMo alloys, the as-cast sample is a body centered cubic (BCC)-ordered solid solution. In FeAlCrMo, it exhibits a dendritic structure, whereas in FeAlCrV, two types of particles are present. The first one is the solid solution V x Cr 1-x (0.8 < x < 1) with the BCC structure and the second one is the V 2 C carbide with orthogonal symmetry. In FeAlCrV, the structure of the investigated material remains stable even after annealing at 800 °C for 15 days. Nevertheless, vanadium starts to redistribute, and the lattice parameter slightly changes at a temperature of 500 °C. Furthermore, a new solid solution enriched in vanadium forms. In FeAlCrMo, a lengthy annealing at a high temperature (800 °C/15 days) results in decomposition into a two-phase material composed of a BCC solid solution and a Mo 3 Al phase with a primitive cubic (PC) structure. Differential scanning calorimetry and dilatometry revealed that decomposition already starts at the temperature of approximately 400 °C. Compression deformation tests were performed at various temperatures starting from room temperature (RT) up to 800 °C. The results showed that both materials exhibit excellent values of yield stress, especially at high temperatures (965 MPa and 898 MPa at 800 °C for FeAlCrV and FeAlCrMo, respectively). The plasticity reaches 5–12% and 3–9%, respectively. [ABSTRACT FROM AUTHOR]

Laser workpiece surface treatment of Al-1.5 wt% Fe alloy with single track was performed with a 2 kW Yb-fiber laser (IPG YLR-2000S). A 3D thermal FEM model has been built to calculate the temperature field and fluid flow field in the molten pool cross-section. Results of numerical simulation, experimental of the micrographs and morphologies were presented, discussed and checked. By FEM the fluid flow due to the Marangoni effect presents two symmetric vortices corresponding to the molten pool center line. The Marangoni effect can lead to mass transfer and interfacial turbulence, when this phenomenon is considered, maximum values of the flow velocity and as well as thermal gradient occur around on the workpiece surface, smaller velocity and thermal gradient occur in the melt pool-substrate interface, thus, the Marangoni effect was more noticeable in lower than in high laser beam velocities. This phenomenon influences and controls the quality, such as, properties of the microstructure, morphological characteristic and as well as quality of laser-treated workpiece tracks, therefore, at low laser beam velocities the morphology is higher and quality of track presents many defects than at high laser beam velocities. Simulation results were assessed with the experimental data, their results were fairly coherent. [ABSTRACT FROM AUTHOR]

A Fe3Al intermetallic alloy has been successfully prepared by the laser-engineered net shaping (LENS) process. The applied process parameters were selected to provide various cooling rates during the solidification of the laser-melted material. The macro- and microstructure and the micro- and macrotexture of Fe3Al samples were investigated. The influence of the cooling rate on grain morphology and texture is discussed. For the applied cooling rate range of 0.64 x 104 K/s-2.6 x 104 K/s, the structure is characterized by the presence of columnar grains for which the growth is directed upwards from the substrate. The intensity of the microtexture varies with the height of the sample and the cooling rate. The intensity of the texture increases with the decrease in the cooling rate. The samples that were obtained with low and medium cooling rates are characterized by the well-developed <100> and <111> macrotextures. The Fe3Al alloy that was produced with a high cooling rate did not show a specific texture, which is reflected in the fairly uniform distribution of the normalized density intensity. Only a very weak texture with a <100> type component was observed. [ABSTRACT FROM AUTHOR]

Low-density steels with different aluminium contents have been investigated with an aim to examine the occurrence of different strengthening mechanisms leading to its higher strength. A composition corresponding to 6.8 wt% aluminium has been studied to understand the underlying strengthening mechanisms. Different factors contributing to the strengthening mechanisms have been separately analyzed. Microstructural features have been analyzed using Mössbauer spectroscopy, small angle X-ray scattering (SAXS), X-ray line profile analysis and transmission electron microscopy (TEM). The enhanced yield strength of the low-density steel containing 6.8 wt% Al was attributed to the strengthening effects arising from the ferrite grain size, dislocations incorporated during processing, ordered phase formation and the presence of Al atoms in the solid solution. Each of these operating mechanisms was modelled by using its constitutive equation for example, grain size strengthening by classical Hall-Petch equation and the strengthening from dislocations by Taylor's equation. In addition, the formation of nano-sized ordered phase was evaluated by TEM, Mössbauer spectroscopy, SAXS and hence order strengthening was modelled by using the size and volume fraction (as determined by TEM and SAXS). Strengthening due to lattice frictional stress required for dislocation motion was also incorporated into the model. [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]

On the Al-rich side of the Fe-Al binary system, the eutectoid decomposition of Fe 5 Al 8 into B2-ordered FeAl and triclinic FeAl 2 in the composition range of 55–65 at.% Al produces an ultrafine lamellar microstructure. The compression creep behavior of such two-phase intermetallic materials was investigated in the temperature range 600–800 °C under constant stress. In addition to the fully lamellar Fe-61Al alloy, Fe-58Al and Fe-62Al that included, pro-eutectoid FeAl and FeAl 2 , respectively, were characterized in terms of their microstructure and creep response. For all microstructures, the strain rate as a function of time and strain exhibits a distinct minimum instead of a steady state creep regime. Microstructure instability, primarily in the vicinity of colony boundaries, is identified as the main reason for the increase in strain rate beyond the minimum. In contrast, lamellar coarsening is shown to be only a secondary factor influencing creep response for the conditions investigated. In comparison to single phase FeAl, the fully lamellar FeAl-FeAl 2 shows enhanced creep resistance while the presence of either pro-eutectoid phase leads to a relative deterioration of the creep resistance. [ABSTRACT FROM AUTHOR]

Binary Fe-Al alloys in the composition range of 53–65 at.% Al contain finely lamellar microstructures formed of the intermetallic phases FeAl and FeAl 2 as a result of a rapid eutectoid decomposition reaction on cooling. Here, we study the effect of ternary additions of up to 2 at.% B, Ti, Cr, Cu and Mo on a fully lamellar alloy with respect to the resulting microstructures, crystal structures of the phases, thermal stability, and mechanical properties. The ternary alloys containing B or Cu preserve the fully lamellar microstructure while those with additions of Mo and Ti show formation of third, ternary phases (Al 8 FeMo 3 and Al 2 FeTi, respectively). Melting temperatures as well as the formation temperatures of the lamellar microstructure are either unaffected or decrease by the ternary additions compared to the binary case. The hardness of the FeAl phase is much more affected by the ternary additions than that of the FeAl 2 phase. The brittle-to-ductile transition temperatures and the yield stresses were studied for all ternary alloys and compared to the binary case, for which also the effect of variations in the Al content was investigated. Especially in case of B additions, an unexpected increase in the brittle-to-ductile transition temperature was observed. Atom probe tomographic experiments reveal that B does not segregate at the phase boundaries but instead forms fine boride particles inside the FeAl lamellae. [ABSTRACT FROM AUTHOR]

The quantitative characterization of the microstructure evolution in high-Mn steel during deformation is of great importance to understanding its strain-hardening behavior. In the current study, in situ high-energy synchrotron X-ray diffraction was employed to characterize the microstructure evolution in a Fe-17Mn-1.5Al-0.3C steel during a tensile test. The microstructure at different engineering strain levels--in terms of ε-martensite and α'-martensite volume fractions, the stacking fault probability, and the twin fault probability--was analyzed by the Rietveld refinement method. The Fe-17Mn-1.5Al-0.3C steel exhibits a high ultimate tensile strength with a superior uniform elongation and a high strain-hardening rate. The remaining high strain-hardening rate at the strain level about 0.025 to 0.35 results from ε-martensite dominant transformation-induced-plasticity (TRIP) effect. The increase in the strain-hardening rate at the strain level around 0.35 to 0.43 is attributed to the synergetic α'-martensite dominant TRIP and twinning-induced-plasticity (TWIP) effects. An evaluation of the stacking fault energy (SFE) of the Fe-17Mn-1.5Al-0.3C steel by the synchrotron measurements shows good agreement with the thermodynamic calculation of the SFE. [ABSTRACT FROM AUTHOR]

The FeAl iron aluminide alloyed by low concentrations of Nb and C ( c , c ) is studied. The influence of the c / c ratio on the structure and high-temperature yield strength of iron aluminide was investigated. The structure and phase composition were studied by scanning electron microscope equipped with EDS and EBSD. The strengthening mechanisms are detected as strengthening by incoherent precipitates of NbC and as a solid solution hardening by Nb atoms. [ABSTRACT FROM AUTHOR]

Iron powders having average particle sizes of ~40 μm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt. %, with an average particle size of ~10 μm. Two different powder metallurgy (PM) techniques, cold and hot pressing, are used to study the effect of the additive element powder on the mechanical properties, wear properties, and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature reaching up to 500 °C at 445.6 MPa. The cold pressing technique was performed at 909 MPa at room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the Brinell hardness number was decreased from 780 to 690 and the radial strength from 380 to 228 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to five times was achieved, compared to the alloy without Al addition for different wear parameters: wear time and sliding speed. [ABSTRACT FROM AUTHOR]

We present an additive manufacturing of thin-walled Fe-Al samples using the Laser Engineered Net Shaping (LENS) technique. Samples in the form of thin walls, ranging from 0.5 to 5 mm in thickness, were manufactured, and their properties were investigated. Cooling rates during deposition were estimated and correlated with the resulting microstructure and properties. It was found that building 0.5 mm walls results in relatively low cooling rates, which led to the formation of the DO 3 type crystal structure, and the B2 structure was found for thicker wall samples. Directly fabricated Fe-Al thin-walled structures were found to possess high metallurgical quality in terms of porosity, but despite their good overall visual appearance, very large cracks were observed after the manufacturing process, which disqualifies them for use in the fabrication process of any mechanical parts. [ABSTRACT FROM AUTHOR]

Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the NiTiFeAlCu high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. NiTiFeAlCu alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Electron beam welding (EBW) technique was used to perform dissimilar joining of plain carbon steel to Fe–7%Al alloy under three different weld conditions such as with beam oscillation, without beam oscillation and at higher welding speed. The effect of weld parameters on the microstructure and mechanical properties of dissimilar joints was studied using optical microscopy, SEM, EBSD, hardness, tensile and erichsen cup tests. Microstructure results show that the application of beam oscillation resulted in uniform and homogeneous microstructure compared to without beam oscillations and higher welding speed. Further, it was observed that weld microstructure changes from equiaxed to columnar grains depending on the weld speed. High weld speed results in columnar grain structure in the weld joint. Erichsen cup test results show that the application of beam oscillation results in excellent formability as compared to high weld speed. Tensile test results show no significant difference in strength properties in all three weld conditions, but the ductility was found to be highest for joints obtained with the application of weld beam oscillation as compared to without beam oscillation and high weld speed. This study shows that the application of beam oscillations plays an important role in improving the weld quality and performance of EBW dissimilar steel to Fe–Al joints. [ABSTRACT FROM AUTHOR]

In the present work, the effect of boron addition on microstructural and magnetic properties of (Fe 75 Al 25 ) 100−x B x (x=0, 5, 9 and 12 at%) alloys prepared by mechanical alloying process, were investigated by X-ray diffraction and vibrating sample magnetometer and SQUID techniques. The microstructural parameters such as the crystallite size, the microstrain and the lattice parameters of the bcc- solid solution Fe(Al) were deduced from the Rietveld refinement of the X-ray diffraction patterns using the X-Pert HighScore. It is found that boron additions delay the formation of the BCC- Fe(Al) solid solution by mechanical alloying. The coercivity (H c ) decreases with increasing the amount of boron added. The undoped sample showed a hard ferromagnetic behavior (Hc~750 Oe) whereas the doped ones reached a softening ferromagnetic behavior (Hc<100 Oe). [ABSTRACT FROM AUTHOR]

FeAlCrNiMo high-entropy alloys were prepared. The effect of Mo content on the microstructure and the properties of the alloys were investigated. When the Mo content was 0.1, the alloys were composed of single BCC solid solution; when Mo content reaches 0.25, the alloys were composed of BCC solid solution and ordered B2 solid solution. When Mo content is more than 0.75, some σ phases emerged. The volume fraction of the second phase increases with the increasing Mo content, and the crystal grains became coarsening. The yield strength, fracture strength, and hardness increase with the increasing Mo content and reach 2252, 2612 MPa, and 1006 Hv, respectively. The magnetic transformation undergoes from the ferromagnetism to paramagnetism with the increasing Mo content. The saturation intensity and remnant magnetism are decreased with the increasing Mo content. [ABSTRACT FROM AUTHOR]

Fe 3 Al alloy with nominal composition 73Fe-25Al-2Cr (at%) was subjected to surface mechanical attrition. The fine structures of surface grains on the Fe 3 Al alloy, which undergone severe plastic deformation, were studied. The results show that nanocrystals about 50 nm in average are produced on the top surface when Fe 3 Al alloy undergoes 5 min attrition. Moreover, some submicron grains about 100–300 nm in size are induced because of the nonuniform strain. The refinement of grains is controlled by dynamical recrystallization mechanism for Fe 3 Al alloy under the condition of severe plastic deformation. The grain refinement leads to the strengthening of Fe 3 Al alloy and the peak hardness reaches HV425 after 5 min attrition. [ABSTRACT FROM AUTHOR]

In the present study, the feasibility of the formation of surface layers containing hard iron aluminides on AA6061-T6 aluminum via pre-plasma spraying with iron and subsequently double surface melting by pulsed Nd:YAG laser is studied. The effects of single and double laser surface melting on microstructure, phase formation, and hardness of the treated layers are examined. Single-step laser treatment resulted in the presence of undissolved iron particles surrounded by lump-like AlFe and needle-like AlFe intermetallic compounds. Double laser surface melting dissolved the retained undissolved irons and resulted in the formation of Al-AlFe eutectic structure. Microhardness profiles along cross section and top surface of the treated layers indicated that laser surface alloying with iron enhanced the hardness of the aluminum to more than twice of that of the base material. [ABSTRACT FROM AUTHOR]

A nanostructured disordered Fe(Al) solid solution was obtained from elemental powders of Fe and Al using a high-energy ball mill. The mechanically alloyed powders were consolidated at room temperature under pressures of 5 and 7 GPa, then annealed at different temperatures for 2 h. The phase transformations occurring in the bulk Fe(Al) solid solutions were studied by X-ray diffraction. Scanning electron microscopy was employed to examine the morphology of the different samples. Fully dense disks with homogenous microstructure were obtained and the bulk materials show grain sizes of 20–40 nm. Electrochemical techniques were used to investigate the effect of consolidation pressure and annealing temperature on the corrosion behavior of Fe(Al) solid solution. The consolidation pressing has no effect on the corrosion behavior of the samples. Lower values for corrosion potential (E corr ) and pitting potential (E pit ) were obtained after annealing at higher temperature (450 and 650 °C). Pitting was initiated preferentially in the metastable intermetallics new phases. [ABSTRACT FROM AUTHOR]

INCOLOY MA956 is a ferritic oxide dispersion-strengthened alloy manufactured by mechanical alloying followed by hot extrusion in vacuum-sealed cans or by degassing and hot isostatic pressing. This could be followed by a tailored heat treatment sequence in order to obtain a desired microstructure and to allow the oxide dispersion to precipitate. Three different oxides, responsible for the high-temperature mechanical strength, have been observed in this alloy: YAlO, YAlO, and YAlO. Their sizes range from just a few to hundreds of nanometers. In this work, mechanically alloyed MA956 powder was consolidated via friction consolidation, a single-step and potentially cheaper processing alternative. Three fully dense compacts were produced. The compacts exhibited a refined, equiaxed grain structure with grain sizes smaller than 10 µm and the desired oxide dispersion. YAlO and YAlO were identified by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction. The size distribution of precipitates above 50 nm showed a direct proportionality between average precipitate size and grain size. The total energy input during processing was correlated with the relative amount of each of the oxides in the disks: the higher the total processing energy input, the higher the relative amount of YAlO precipitates. The elemental composition of the oxide precipitates was also probed individually by EDS, showing an aluminum enrichment trend as precipitates grew in size. [ABSTRACT FROM AUTHOR]

The oxidation behavior of binary Fe-Al alloys with an aluminum content between 58 and 64 at.% was studied by isothermal and cyclic oxidation experiments in a temperature range of 900-1000 °C. The parabolic rate constants were determined to be comparable to those of B2-ordered Fe-48Al. All investigated alloys exhibited a fine-scaled, lamellar microstructure (<300 nm lamellar spacing), which was a result of the eutectoid decomposition of the high-temperature phase FeAl into FeAl and FeAl. None of these two phases showed a preferential oxidation. At 900 °C θ-AlO formed, whereas at 1000 °C a transformation of the initially formed θ-AlO to the slower growing and passivating α-AlO was confirmed by grazing incidence X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

The effect of Nb and C additions on the phase composition, microstructure, and creep resistance of FeAl-type alloys is investigated. Two alloys, which contained (at. pct) (i) 27.6 Al, 1.15 Nb and 0.19 C (Fe balance) and (ii) 27.1 Al, 1.11 Nb, and 0.76 C (Fe balance), were studied in a temperature range from 873 K to 1073 K (600 °C to 800 °C). The carbide in both alloys was identified as NbC. The creep data can be rationalized by introducing a threshold stress, below which, the creep rate is negligible. The threshold stress and an effective stress exponent were found simultaneously by a numerical method. Using the obtained values of the threshold stress, the activation energy of creep was determined to be 328 kJ/mol. The effective stress exponent varied from 2.0 to 3.1. A breakdown of power-law behavior was observed at higher stresses. The transition occurred at the normalized creep rate of $$ \dot{\varepsilon }/D = 10^{13} \,{\text{m}}^{ - 2} $$ , which agrees with the rule suggested by Sherby and Burke and the diffusion coefficient D corresponding to the diffusion of Al in Fe-Al. [ABSTRACT FROM AUTHOR]

Aluminum alloys welding with steels is one of the most complex joining cases approached historically at industrial and research level. The increasing diffusion of aluminium alloys in the automotive, shipbuilding and sometimes in the Oil&Gas Industry (for platforms and offshore construction) and the need of joining them with steels of different grades is a challenge for designers and welding engineers both from the point of view of welding technology that of metallurgy, taking into due account the peculiarity of the iron - aluminium system. By examining the state of the art, it is possible to observe that well established welding process (such as explosion and friction welding) are deeply employed for the production of bimetallic transition joints; on the other hand, GMAW or laser weld brazing and Friction Stir welding seem to be the most promising processes for the near future. In this article, the author tries to propose the state-of-the-art of this subject with an overview of the future perspectives. [ABSTRACT FROM AUTHOR]

Fe–15Al–10Nb (at.%) alloys containing Laves phase fibers embedded in a disordered α-(Fe,Al) matrix were investigated in as-cast, heat treated and directionally solidified condition. Microstructure consisted of either duplex structure of primary dendrites and eutectic (as-cast and heat treated) or fully eutectic structure (directionally solidified). Nanoindentation on the Laves phase fibers revealed their anisotropic features as well as the onset of dislocation plasticity. Compression testing showed the yield strength anomaly, which occurred in the 500–650 °C range. Directional solidified alloy exhibited the lowest strength fracture toughness whereas the as-cast alloy had the highest strength and fracture toughness. The value of stress exponent obtained from the strain rate dependence of the flow stress indicated that the dislocation climb mechanism dominated the creep process. Deformation mechanisms were also discussed and related to the microstructure evolution. [ABSTRACT FROM AUTHOR]

Highlights: [•] ARB led to a strong grain refinement (down to 0.5μm) and homogeneity upon straining. [•] The fraction of high-angle boundaries is ∼60% in the alloy after ARB. [•] The texture after ARB is characterized by typical C shear component near the surface. [•] Copper/Dillamore component is observed at the mid-thickness of the sheets. [ABSTRACT FROM AUTHOR]

Iron aluminide alloys are advanced structural materials with promising properties for elevated temperature applications in a hostile environment. They offer a combination of unique properties such as corrosion and wear resistance, high temperature strength, lower density and cost advantage over the Fe–Cr or Fe–Cr–Ni stainless steels. In our work, the deformation behavior of a Fe–16Al–5Cr–1Mo–0.1Zr (at.%) alloy (hereafter known as Fe–16Al) under hot compression conditions was characterized in the temperature range 600–1100 °C and strain rate range 10 −3 –10 2 s −1 . Processing maps were calculated to evaluate the efficiency of the hot working and to recognize the instability regions of the flow behavior. The isothermal, constant-strain rate compression tests were carried out on a Gleeble 3800 testing system. The flow stress was found to be strongly dependent on temperature and strain rate. At higher strain rates or lower temperatures, the Fe–16Al alloy exhibited a flow-softening type of stress–strain curve, while at lower strain rates or at higher temperatures, the flow curves were of a steady-state type. The tested alloy possesses the optimum hot working condition domain above 750 °C at 10 − 1 –10 −2 s −1 for ε = 0.6, since the material undergoes dynamic recrystallization to produce a fine-grained structure ( d eq ≈ 20–50 μm) with a high fraction of high angle boundaries (~ 40%) and the peak efficiencies ( η = 56% at 750 °C and 10 −3 s −1 ). These results have been related to the earlier reported results, achieved for two intermetallic alloys: Fe 3 Al (Fe–28Al–5Cr–0.08Zr–0.04B at.%) and FeAl (Fe–36Al–0.22Mo–0.05Zr–0.01B at.%). [ABSTRACT FROM AUTHOR]

This article is part of the research on the microstructural phenomena that take place during hot deformation of intermetallic phase-based alloy. The research aims at design an effective thermo - mechanical processing technology for the investigated intermetallic alloy. The iron aluminides FeAl have been among the most widely studied intermetallics because their low cost, low density, good wear resistance, easy of fabrication and resistance to oxidation and corrosion. There advantages create wide prospects for their industrial applications for components of machines working at a high temperature and in corrosive environment. The problem restricting their application is their low plasticity and their brittle cracking susceptibility, hampers their development as construction materials. Consequently, the research of intermetallic-phase-based alloys focuses on improvement their plasticity by hot working proceses. The study addresses the influence of deformation parameters on the structure of an Fe-38% at. Al alloy with Zr, B Mo and C microadditions, using multi - axis deformation simulator. The influence of deformation parameters on microstructure and substructure was determined. It was revealed that application of cumulative plastic deformation method causes intensive reduction of grain size in FeAl phase base alloy. [ABSTRACT FROM AUTHOR]

The iron aluminide Fe3Al has been successfully processed by selective laser melting (SLM) and laser metal deposition (LMD). Process parameters have been determined by which defect free and dense (>99.5%) samples were produced. However, due to the low thermal conductivity of Fe3Al, preheating the substrate to 200 °C was necessary to prevent cracking during cooling. Microstructural characterization by electron backscatter diffraction (EBSD) showed that in spite of the high cooling rates large elongated grains grew in the building direction, more distinctive for SLM than for LMD. These grains show a continuous change in the crystallographic orientation. Evaluation of the compressive flow stress showed that the anisotropic microstructure results in anisotropic mechanical properties, depending whether the samples are loaded in building direction or perpendicular to it. The alloy shows a very high strength up to 600 °C and – concerning the coarse microstructure – becomes ductile already at low temperatures. [ABSTRACT FROM PUBLISHER]

Four quinary Fe-Al-Mo-Ti-B and Fe-Al-W-Ti-B alloys based on Fe3Al produced by vacuum induction melting were investigated regarding their microstructure and mechanical properties. The microstructures consist of a Fe3Al matrix with complex borides along grain boundaries. Compared to other Fe3Al-based alloys the present alloys show favourably low ductile-to-brittle transition temperatures (BDTT) and a markedly high creep strength at 650°C. The latter is most pronounced for an alloy whose strength, besides strengthening by solid solution hardening through Mo and by the boride precipitates, is further enhanced by stabilising the D03-ordered structure up to higher temperatures. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Fe–Al alloying in a presence of Fe2O3 is detected after 2h of milling. [•] The Fe–25at.% Al substitutional solid solution is formed. [•] Next milling steps yield Al decrease in the alloy and hematite dissolution. [•] Dynamic process is reflected by changes in magnetic properties. [•] Intergrain exchange coupling yields dipolar interactions at low magnetic fields. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and mechanical properties of a Fe–15Mn–1.5Al–0.6C TWIP steel with and without rare earth (RE) addition were investigated. The RE-alloyed steel showed both improved tensile strength and total elongation (TEL). Optical microscopy and electron back-scattered diffraction (EBSD) characterizations showed that the RE-alloyed steel possessed a more homogeneous microstructure and a larger fraction of high-angle grain boundaries, which increased the TEL. Meanwhile, EBSD and transmission electron microscope (TEM) analyses indicated that the RE-alloyed steel exhibited more uniform distributed annealing twins and secondary annealing twins with a thickness of 10–20nm appeared in some grains, which resulted in the higher tensile strength. [Copyright &y& Elsevier]

Abstract: Fatigue studies were conducted under load control with a servo-hydraulic testing machine with smooth specimens of the aluminum wrought alloys EN AW-6056-T6 (R m =399MPa) and EN AW-6082-T5 (R m =356MPa) up to a maximum number of N =2×108 and 109 cycles, respectively. The results show for both aluminum alloys that the fatigue strength decreases with increasing number of cycles after the kneepoint of the S–N-curve and that approximately at this point a transition of the crack initiation site from the surface to the subsurface occurs. All fractured specimens were investigated with a scanning electron microscope (SEM). Large defects like primary intermetallic particles could not be found at the crack initiation sites. The difference between the subsurface non-defect crack initiation sites of both alloys is to be found in the fractographic structure. The internal crack initiation site of EN AW-6056-T6 shows a multiplicity of cleavage-like planes contrary to the flat area found at the alloy EN AW-6082-T5. These results were already presented in [1]. The scope of this present paper is new microstructural investigations and the formulation of a failure model which respects the results of different scales of microscopy. Electron back scatter diffraction analysis (EBSD analysis) and transmission electron microscopy (TEM) were done for both alloys to characterize the microstructure and to compare unstressed and tested materials. These differences are discussed with regard to the differences in failure mechanisms. [Copyright &y& Elsevier]

In this paper, fabrication of open-celled porous Fe-10%A1 foam by space-holder technique in which NaCl powder and polyester resin were utilized as space holder and binder respectively to generate 30-80% porosities was studied. FeAl solid solution was prepared via mechanical alloying method after 25 h high energy milling process. The results indicate that the size and shapes of the pores are determined by the size and shapes of NaCl particles. Also, when compaction pressure was in the range of 70-150 MPa and the sintering process was performed at temperature around 1100°C, the samples had the best quality. Microstructure observations show the pore size was in the range of 200-500 μm. [ABSTRACT FROM AUTHOR]

Nanocrystals were produced on the surface of FeAl intermetallic compound by a severe plastic deformation technology-surface mechanical attrition. The phase and grain evolutions were characterized through x-ray diffraction technology, transmission electron microscopy, and Mossbauer spectroscopy. The results show that surface grains are refined to 15 nm in average size after 60 min of attrition. The surface grains present inhomogeneity due to the nonuniform plastic deformation when the attrition time is less than 15 min. Large quantities of dislocations and tangles of dislocations are observed in those larger grains. AlCr phase forms on the surface of FeAl samples which have undergone attrition for less than 15 min. When the attrition time increases, the AlCr phase becomes disordered and dissolves into the matrix. In addition, disordering of FeAl occurs only in a very thin area during severe plastic deformation. [ABSTRACT FROM AUTHOR]

Porous ceramic matrix composites FeAlO/FeAl with incorporated metal inclusions (cermets) were synthesized by pressureless method, which includes hydrothermal treatment of mechanically alloyed FeAl powder followed by calcination. Their main structural, textural and mechanical features are described. Variation of FeAl powder alloying time results in non-monotonous changes of the porosity and mechanical strength. Details of the cermet microstructure and its relation to the mechanical properties are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The mechanically alloyed and milled Fe–Al alloys under nitrogen were prepared. [•] Formation of iron nitride was achieved in the mechanically alloyed Fe–Al. [•] An influence of this nitride on magnetic hardening of final material is shown. [Copyright &y& Elsevier]

Highlights: [•] Surface laser remelting process modifies the surface film improving considerably its microstructure. [•] A great improvement in the performance of corrosion was confirmed on the laser-treated alloy. [•] Was showed a greater range of passivity, high polarization resistance and a lower area of the hysteresis loop. [•] The laser-treated layers serve as an effective barrier to protect the matrix against corrosion attacks. [•] The application possibilities of this technique may be in aeronautic, automotive, energy, etc. [ABSTRACT FROM AUTHOR]

Abstract: Al–8wt%Fe, a hypereutectic alloy, was studied under electromagnetic levitation (EML) solidification conditions in both terrestrial and reduced gravity conditions. The latter was carried out on the A300 aircraft using the TEMPUS facility. The solidified samples were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction and neutron diffraction techniques. The results are interpreted in the light of the temperature–time measurements taken in situ during the solidification process in the EML. It is shown that both samples experienced some undercooling for the solidification of the primary Al–Fe intermetallic phase, which is likely Al m Fe. The solidification path continues with the nucleation and growth of Al13Fe4 followed by primary α-Al. These last two phases do not seem to show any measureable undercooling and recalescence events. Finally, the metastable Al x Fe (where x =5) nucleates starting with the formation of eutectic. This metastable intermetallic continues the eutectic growth as Al13Fe4. The morphology differences of the intermetallics growing under terrestrial and reduced gravity conditions are clear with acicular morphology for the former and a star like morphology for the latter. The primary α-Al has a clear strong textured structure in the reduced gravity sample, while a weak one is observed in the terrestrially processed sample. The difference in texture is attributed to the weaker fluid flow occurring in the droplet under reduced gravity conditions while the difference in the morphology of the primary intermetallic is attributed to the higher cooling rate experienced by the reduced gravity sample compared to that for the terrestrially processed sample. [Copyright &y& Elsevier]

Abstract: Fe3Al–20wt.%Al2O3 ultrafine grained composites with 4wt.% Cr were prepared by mechanical alloying inducing self propagating high temperature synthesis with subsequent plasma activated sintering. Microstructures of the composites were studied by X-ray diffraction, scanning electron microscopy, energy dispersive spectrum and transmission electron microscope. Then the relative density, room temperature hardness, static corrosion resistance and dry sliding wear behavior at a temperature range of 25°C–800°C of the sintered samples were tested and analyzed. The results showed that the composites had high hardness and a good microstructure with fine grain size, high relative density. The composites with 4wt.% Cr amount also exhibited excellent comprehensive tribological properties at medium–high temperatures especially at a temperature above 500°C, although the wear resistance did not be improved at 25°C–500°C. 4wt.% Cr element addition improved the corrosion resistance of the composites significantly with the corrosion loss decreasing by 19.48%. [Copyright &y& Elsevier]

Abstract: Pore structure control methods for porous FeAl intermetallics were studied in this paper based on pore formation mechanism. A large range of pore structure parameters can be obtained through fabrication parameter adjustment in porous FeAl preparation procedure. Open porosity and maximum pore size of porous FeAl have a direct proportional relationship to the powder size of raw materials and an inversely proportional relationship to the pressing pressure. The relationship between maximum pore size (d m) and raw material powder size (d p) can be determined as . Open porosity and maximum pore size decrease with increasing holding time at solid diffusion reactive procedure. The quantitative relationship between open porosity (θ) and holding time (t) at 600 °C is ; the quantitative relationship between maximum pore size (d m) and holding time (t) at 600 °C is . [Copyright &y& Elsevier]