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The objective of this study was to evaluate the effect of milling time, milling speed and particle size of initial powders on the coating thickness of Fe-Al intermetallic coating by using artificial neural network (ANN). Coating morphology and cross-section microstructures were evaluated using a scanning electron microscope (SEM). It was found that an increase in the milling time provided an increase in the coatinglayer thickness due to the cold welding process between particles and the steel substrate. The microstructure of the coating surface was refined by ball impacts in the milling process. As a result of this study, the ANN was found to be successful for predicting the coating thickness of Fe-Al intermetallic coatings. The correlation between the predicted values and the experimental data of the feed-forward back-propagation ANN was quite adequate. The mean absolute percentage error (MAPE) for the predicted values didn't exceed 7.46%. The ANN model can be used for predicting the coating thickness of Fe-Al intermetallic coating produced for different milling time, milling speed and particle size. [ABSTRACT FROM AUTHOR]

An Fe-Al coating consisting of FeAl and Fe3Al was prepared on AISI 1045 steel by hot-dip aluminizing and subsequent high-temperature diffusion. Dry sliding wear tests were performed for Fe-Al coating against AISI 52100 steel under various sliding speeds and loads. During sliding, thin tribolayers formed on the worn surfaces of the Fe-Al coating. After wear, they were observed to be a nonoxidized mechanically mixed layer (MML) at 0.5 m/s, an oxide-containing MML at 0.75–2.68 m/s, and an in situ oxide layer at 4 m/s. The tribolayers presented a close relation with the wear behavior. Because of their different ingredients, structures, and types, the tribolayers resulted in significant changes in the wear behavior. At 0.75–2.68 m/s (except for 2.68 m/s, 40 N), the compact tribooxide layers exerted a protective function for Fe-Al coating to reduce the wear rate. However, for the tribolayers containing no or trace tribooxides at 0.5 m/s or the unstable ones formed at 2.68 m/s, 40 N and 4 m/s, no protection was presented. In these cases, the Fe-Al coating would be partly or totally ground off, thus presenting poor wear resistance at high wear rates. [ABSTRACT FROM AUTHOR]

In the present work, Fe/(Zn-11Al-3Mg-0.2Si) solid–liquid diffusion couples were held for different time periods at temperatures from 480 to 650°C to investigate the growth of Fe–Al layers. We found that FeAl3and Fe2(Al, Si)5phases formed on the diffusion couple interface; Si solubility in Fe2(Al, Si)5was 1.4 at.% and the overall Fe–Al layer growth-rate time constant from 500 to 650°C ranged from 0.53 to 0.37. The layer growth rate was controlled by the inter-diffusion of Fe and Al. The overall Fe–Al layer kinetics of growth equation is. Overall Fe–Al layer thickness in the Fe/(Zn-11Al-3Mg-0.2Si) diffusion couple increased as temperature increased. [ABSTRACT FROM PUBLISHER]

The effect of twin-arc surfacing conditions using aluminium and steel electrode wires on the chemical composition of deposited metal is investigated. The effect of the chemical composition on the mechanical and service properties of deposited layers is described and the efficiency of using intermetallic alloys of the iron–aluminium system as permanent protective coatings of casting moulds is confirmed. [ABSTRACT FROM AUTHOR]

Fe–Al is one of the best corrosion resistant alloys at high temperatures. The flip side of Al addition to Fe is the deterioration of the mechanical properties. This problem can be solved by adding a suitable amount of third alloying component. In the present work, we useab initiocalculations based on density functional theory to study the elastic properties of FeCrAlalloys for Al and Cr contents up to 20 at.%. We assess the ductility as a function of chemistry by making use of the semi-empirical correlations between the elastic parameters and mechanical properties. In particular, we derive the bulk modulus to shear modulus ratio and the Cauchy pressure and monitor their trends in terms of chemical composition. The present findings are contrasted with the previously established oxidation resistance of Fe–Cr–Al alloys. [ABSTRACT FROM PUBLISHER]

The Fe3Al alloy with D03structure exhibits large recoverable strains due to reversible slips. Tension and compression experiments were conducted on single crystals of Fe3Al, and the onset of slip in forward and reverse directions were obtained utilizing high-resolution digital image correlation technique. The back stress provides the driving force for reversal of deformation upon unloading, resulting in a superelastic phenomenon as in shape memory alloys. Using density functional theory simulations, we obtain the energy barriers (GSFE – generalized stacking fault energy) for {1 1 0}〈1 1 1〉 and {1 1 2}〈1 1 1〉 slips in D03Fe3Al and the elastic moduli tensor, and undertake anisotropic continuum calculations to obtain the back stress and the frictional stress responsible for reversible slip. We compare the theoretically obtained slip stress magnitudes (friction and back stress) with the experimental measurements disclosing excellent agreement. [ABSTRACT FROM PUBLISHER]

The article presents a study on the relationship between damping behavior, magnetic response and order degree in iron (Fe)-based allows. The study found that the magnetic response of ordered allows depends on the order degree. A large hysteresis between the heating and cooling during thermal cycles was exhibited by the damping behavior for Fe-6A1-9Si.

Preliminary results on magnetic and transport properties of a thin film of disordered Fe2CrAl deposited on (111) Si by pulsed laser deposition is reported in this study. While the bulk arc melted ingot used as target for the deposition is purely ferromagnetic, the film shows the co-existence of different magnetic phases, which arises due to the granular nature of the film. This is because, although the average composition pertains to Fe2CrAl, local disorder results in the formation of grains with different magnetic states that may be ferromagnetic or may consist of magnetic clusters. The resulting magnetic inhomogeneity of the thin film leads to large values of negative temperature coefficient of resistance of ∼22%/K at 260 K. [ABSTRACT FROM AUTHOR]

Influence of processing conditions onin situgeneration of nanocrystalline Fe3AlCxand Fe–Al phases during mechanically activated annealing and sintering of Fe–40 at% Al alloy was evaluated. Fe3AlCx, Fe3Al and ordered FeAl phases evolved even at a low temperature of 400°C. The presence of carbide phase was attributed to the free carbon originating from the organic process control agent while its formation at low temperature was correlated to fast diffusion of C in the lattice assisted by the nanocrystalline structure coupled with the presence of thermal vacancies in the Fe–40 at% Al alloy. The as-sintered composite showed improved mechanical properties. [ABSTRACT FROM AUTHOR]

Thermoelectric power (TEP) studies on low-density interstitial-free iron-aluminium alloys reveal that the TEP decreases with increase in the aluminium content on account of the introduction of lattice dispersion centres. The TEP coefficients, determined from the Nordheim-Gorter law, for 6.8 and 8.1 wt.% aluminium additions to α-iron are found to be higher than values reported in previous literature for small aluminium additions. The grain size has a very weak effect on the TEP of these alloys. [ABSTRACT FROM AUTHOR]

The reverse α–α′ phase separation in Fe-20Cr-6Al alloys has been monitored by differential scanning calorimetry in as-hot rolled and recrystallized samples previously aged at 435 °C. The splitting in the position of the minima, and the increasing enthalpy change involved, might be explained in terms of dissolution ofα′ particles with different compositions and volume fractions. These results are fully consistent with theα–α′ phase separation kinetics determined by atom probe tomography during ageing at 435 °C. The monitoring of activation energy forα′ dissolution indicates that it is faster in as-hot rolled samples. Finally, the activation energy evolution indicates that there is first a dissolution ofβ′ Fe(AlTi) phase followed byα′ dissolution. [ABSTRACT FROM AUTHOR]

It is well known that the addition of a solute can change both work-hardening characteristics and yield stress; however, there are few available models which describe the role of a solute in relation to both the isotropic and kinematic aspects of work hardening. The current work extends the well-established approach of Kocks and Mecking to include the occurrence of cross slip and its dependence on solute content. The proposed model is compared with experimental data for the system Fe–Al by reference both to the observed work hardening in monotonic loading and the Bauschinger effect measured in reverse shear tests. The agreement between the model and the experimental data is satisfactory and suggests a new description of work hardening which includes a prediction of the ratio of isotropic and kinematic hardening for a given solute content. [ABSTRACT FROM AUTHOR]

Dislocation nucleation in solid solutions of body-centered-cubic intermetallic Fe3Al alloys was investigated by means of nanoindentation and measurement of the pop-in load of samples with different Cr content. It is clearly shown that the Cr solute element in the Fe3Al intermetallic alloy increases the pop-in load, i.e. shear stress, required for dislocation nucleation in a previously dislocation-free region. Changes in pop-in load track closely with changes in elastic properties, which can be interpreted within the framework of the universal features of metallic bonding as a change in the interatomic potential, as proposed by Rose et al. [ABSTRACT FROM AUTHOR]

Bulk-ordered nanocrystalline FeAl intermetallic compound with a grain size of 35 nm was prepared using severe plastic deformation. Nanocrystalline and coarse-grained counterparts with a grain size of 160 nm were subjected to 1.5 MeV Ar+ ion irradiation at room temperature. Enhanced irradiation resistance of nanocrystalline FeAl has clearly been identified by means of grazing-incidence X-ray diffraction and Mössbauer spectroscopy. At the identical damage dose, the nanocrystalline FeAl retains long-range ordering in the B2-superlattice structure, while the coarse-grained state becomes already substantially disordered. The present experimental studies verify that fully dense ordered intermetallic alloys are promising candidate materials for radiation environments. [ABSTRACT FROM AUTHOR]

Argon-arc facing processes of the wear-resistant iron-aluminide-based coatings using filler wire of the aluminium-magnum system are studied. Conditions effect on the geometries, chemical composition, and properties of the deposited bead are established. [ABSTRACT FROM AUTHOR]

In this study, Fe-Al binary oxide was synthesized and evaluated for arsenic removal. Due to its large surface area, Fe-Al mixed oxide shows four times higher As(V) and As(III) adsorption capacity than conventional iron oxide. For a comparative study, single metal oxides such as iron oxide and aluminum oxide are also synthesized. The physical and chemical characteristics of the prepared adsorbents are analyzed by SEM, XRD, and BET analyzer. Through the adsorption isotherm and pH effect experiments, it is discovered that Fe-Al binary oxide shows excellent arsenic adsorption capacity compared with single metal oxides. [ABSTRACT FROM AUTHOR]

This study investigates the wear and corrosion properties of Al-7Si-0.3Mg (A356) alloys fabricated by the spinning deformation processing (SDP). Optical microscopy (OM) and scanning electrical microscopy (SEM) analysis indicate that the SDP virtually eliminates casting defects by elongating the microstructure. The microstructure is improved during SDP by the break-up and dispersion of the eutectic silicon phase throughout the Al-matrix. In a sliding wear environment, the enhanced microstructure diminishes crack nucleation, thus improving the longevity of alloys. In addition, the modified corrosion susceptibility during SDP protects the inter-dendritic region from the corrosion. As wear-corrosion test, the improvement of wear resistance caused by SDP diminishes synergistic attack of wear and corrosion, decreasing the wear-corrosion rate of A356 alloys. [ABSTRACT FROM AUTHOR]

Iron aluminide intermetallic compounds are well known for their high temperature oxidation resistance. In an effort to increase high temperature oxidation resistance of UNS 430 stainless steel, iron-aluminum intermetallic coatings with high iron content were grown on the substrate by the pack cementation technique. The microstructure and composition of the phases were characterized and the effects of pack cementation process parameters on the aluminide coatings were examined. Optoelectronic evaluation indicated that the formation of different stoichiometries of iron aluminide on the surface is controlled by outward diffusion of elements from the substrate. [ABSTRACT FROM AUTHOR]

Chemical, microstructural, and mechanical properties of nanocrystalline FeAl intermetallic alloys with Li, Ce, and Ni additions have been assessed. Mechanical alloying and sintering procedures were used to produce and consolidate the alloys. The sintering procedure was based on room temperature uniaxial pressing followed by annealing in air of the pressed specimens. The mechanically alloyed powders have a microstructure consisting of micrometer-size particles that contain FeAl intermetallic nanocrystals. The three minor additional elements form a solid solution with the B2 intermetallic structure of the FeAl alloy. Densification greater than 90% has been obtained. The hardness values are higher than those obtained from specimens produced with conventional casting procedures. High resolution transmission electron microscopy images showed clusters of less than 5 nm with well-defined structure corresponding to Fe 3 Al. [ABSTRACT FROM AUTHOR]

The atomic structure and composition of a recently reported second phase found in Fe-Al alloys with small B and C additions have been determined using a combination of Z-contrast imaging and electron-energy-loss spectroscopy. The structure of this ordered tetragonal precipitate is found to be closely related to the B2 structure of the matrix. The derived structure and electron-energy-loss spectroscopy indicate that the phase is a new low-metalloid-content boride with B occupying specific interstitial sites. [ABSTRACT FROM AUTHOR]

A phenomenological model is introduced for the temperature dependence of the yield strength of Fe-Al. The key feature of the model is that it incorporates hardening by thermal vacancies to account for the yield strength anomaly. Since the vacancy concentration C varies as exp (- 1 / T ) and the hardening due to V vacancies varies as C 1/2, the model predicts at intermediate temperatures an V exponential increase in strength with increasing temperature. This increasing strength is terminated by the onset of dislocation creep. The model includes strain rate dependences that are consistent with experimental observations and yields an activation enthalpy for vacancy formation which is in excellent agreement with a previously measured value. [ABSTRACT FROM AUTHOR]