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Erosion testing was conducted on cast steel and spheroidal graphite cast iron specimens containing large amounts of manganese and several other ferrous materials in molten aluminum alloys. Based on the results, the erosion resistance of ferrous materials with a high-Mn content was quantified, and the resistance mechanism was investigated. The erosion ratios of high-Mn-containing ferrous specimens were lower than those of specimens that did not contain a high amount of Mn. An analysis of the chemical compositions in the vicinity of the contact interfaces of the high-Mn-containing specimens after testing revealed that the manganese-to-iron content ratios in the intermetallic layers were largely the same as those in the specimens and that the ratios in the melts (solidified) were greater than those in the specimens and intermetallic layers. This small-scale enrichment of manganese could be attributed to its lower diffusion rate compared to iron. In addition, the calculated isothermal phase diagrams corresponding to the testing temperature showed that the apparent saturation solubility of iron in the molten aluminum alloys decreased with the manganese content, irrespective of the silicon content in the melts. These results suggest that the local decrease in the saturation solubility of iron in the melts owing to the small-scale enrichment of manganese in the vicinity of the solid–liquid interface can improve the erosion resistance of specimens containing a high amount of manganese. [ABSTRACT FROM AUTHOR]

The thermodynamic properties for the full composition range of liquid Fe–Ti alloys were determined using the atom and molecule coexistence theory (AMCT). The thermodynamic model was also established to calculate the mass action concentration (activity) of the structural units in the above-mentioned binary alloy system. The temperature dependence of the activity coefficients of Ti dissolved in molten iron to form dilute solutions () relative to pure liquid, were also estimated. Simultaneously, the standard Gibbs free energy changes of dissolving Ti in the iron of liquid Fe–Ti were also studied. The excess molar mixing enthalpy , the excess molar mixing entropy , and the excess molar mixing Gibbs free energy were also studied from 1873 to 2073 K. Meanwhile, the thermodynamic properties of activities and the excess Gibbs free energy of mixing were predicted in the Fe–Al–Ti ternary melts at 1873 K under conditions of various Fe/Al ratios. [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]

Ductile iron containing Si and Mo (SiMo) is a common alloy that has been used for exhaust car manifolds due to the need for high thermal cycling and being in an oxidizing environment. Al alloying has been shown in previous studies to reduce surface degradation during high temperature exposure of SiMo ductile iron. However, it has been shown to decrease the ductility and increase cracking during thermal cycling due to graphite shape degradation. To optimize composition and casting technology of Al-alloyed SiMo ductile iron, experimental castings containing 0.0% Al (base), 1.8% Al, and 3% Al were produced using a special melting procedure and tested at high temperature. Through experimental results and analysis, it was determined that the optimal Al alloying was dependent on a balance of oxidation and thermomechanical conditions. [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]

In solid-solution-strengthened ferritic ductile iron (SSFDI), a silicon content above 4.3 wt% leads to an abrupt decrease in ultimate tensile strength and elongation at fracture. This phenomenon has recently been proven to be attributed to the formation of iron–silicon long-range orderings that lead to an embrittlement of the material. It is assumed that the local tendency to form silicon superstructures is promoted in particular by the occurrence of silicon microsegregation. During solidification of ductile iron, silicon segregates inversely into the austenite. Thus, the highest silicon concentration is larger than the initial concentration of the melt and is located directly at the graphite nodules. As a straight consequence, the presence of silicon superstructures is expected primarily in these areas. Therefore, the focus is on homogenization of the silicon microsegregation profile in order to avoid the formation of brittle iron–silicon superstructures. For this purpose, in the present study the alloying concept of SSFDI is adapted. Thermodynamic–kinetic simulations as well as experimental investigations indicate that aluminum concentrations of approx. 1.2 wt% lead to an inversion of the silicon microsegregation. The findings provide a promising tool to shift the silicon embrittlement in SSFDI to higher silicon concentrations. This method could be used to increase the maximum strength, to improve toughness properties or to increase the process integrity against deviations in silicon content. [ABSTRACT FROM AUTHOR]

The application of an alternative laser-induced breakdown spectroscopy (LIBS) method based on transversely excited atmospheric (TEA) CO2 laser was investigated for the first time for estimating the hardness of metallic materials. The human eye-safe (TEA) CO2 laser, operating at 10.6 µm, was used for plasma generation. The LIBS spectra were recorded by employing a cost-effective CCD camera for the time-integrated and spatial resolved measurements. The cast iron and aluminum alloys samples with different hardness have been tested. The ratio between the magnesium ionic and neutral lines in LIBS spectra was applied for estimating the material hardness. In addition, the hardness of all samples included in this study was determined using the conventional method for material hardness determination, i.e. Vickers hardness test. The linear dependence of magnesium lines intensity ratio on the sample's hardness was obtained for both kinds of materials. Profilometric measurements were used to verify that the newly-introduced method is almost nondestructive for the investigated metals. The results obtained in the present work confirmed the potential of using this original LIBS system not only for the fast elemental analysis but also for the direct estimation of the hardness of metals and alloys. [ABSTRACT FROM AUTHOR]

To further investigate the effects of isothermal heating temperature on the interfacial reactions between the Fe-Al-Ca alloy and the Al2O3-CaO-FeO oxide, two kinds of diffusion couples with different FeO contents in the oxide were prepared and then subjected to isothermal heating at different temperatures in the range of 873 K to 1473 K for 10 h, 30 h, and 50 h. With increasing temperature of isothermal heating, in the case of 0.5 mass% FeO, fine Al2O3 particles first precipitated in the alloy near the alloy–oxide interface, and then CaO·Al2O3 branch inclusions appeared and increased in number, while for the case of 3.0 mass% FeO, Al2O3 particles were the only reaction product in the particle precipitation zone (PPZ). An improved kinetics model for predicting PPZ width was proposed and verified by experimental results. [ABSTRACT FROM AUTHOR]

This study analyzes the effects of manufacturing parameters such as the temperature and heating time on the shape and size of high-aluminum-phase precipitates produced from a 95.5 wt pct Al and 4.5 wt pct Fe powder mixture. The samples were prepared by powder metallurgy, and the changes in the heat flux during the simulation of the sintering process by differential thermal analysis were recorded to determine the temperature of the transformation. To identify the resulting structures, microscopic observations (scanning electron microscope) and chemical composition analyses were performed simultaneously. The distribution and shape of the resulting high-aluminum-phase precipitates were determined. Microhardness measurements were also performed, and Meyer's law and Kick's similarity law were applied to the results to analyze the influence of the high-aluminum phases on the reinforcement of the aluminum matrix. [ABSTRACT FROM AUTHOR]

Determining the dominant creep mechanism is the key feature for design and development of Al-Fe alloys. The tensile creep behavior of Al5Fe4Cu2ZnMnMg alloy (AF1) and Al5Fe4Cu2CrZnZrMnMg alloy (AF15) by prepared semisolid forming has been investigated. The results reveal that the steady-state creep rates of the AF1 and AF15 alloys are increased with increasing temperature and applied stress. The creep property of the AF15 alloy is slightly higher than that of the AF1 alloy. There is threshold stress during creep. The creep true stress exponent is close to 5. The creep mechanism of the alloys is controlled by the lattice diffusion of aluminum. The creep resistance of the AF15 alloy is significantly improved by adding a small amount of Cr and Zr elements The reasons for the improved creep life of the AF15 alloy are discussed. [ABSTRACT FROM AUTHOR]

This study documents laboratory-scale observations of reactions between Fe-Al alloys (0.1 to 2 wt pct Al) with slags and refractories. Al in steels is known to reduce oxide components in slag and refractory. With continued development of Al-containing Advanced High-Strength Steel (AHSS) grade, the effects of higher Al must be examined because reduction of components such as CaO and MgO could lead to uncontrolled modification of non-metallic inclusions. This may lead to castability or in-service performance problems. In this work, Fe-Al alloys and CaO-MgO-Al2O3 slags were melted in an MgO crucible and samples were taken at various times up to 60 minutes. Inclusions from these samples were characterized using an automated scanning electron microscope equipped with energy dispersive x-ray analysis (SEM/EDS). Initially Al2O3 inclusions were modified to MgAl2O4, then MgO, then MgO + CaO-Al2O3-MgO liquid inclusions. Modification of the inclusions was faster at higher Al levels. Very little Ca modification was observed except at 2 wt pct Al level. The thermodynamic feasibility of inclusion modification and some of the mass transfer considerations that may have led to the differences in the Mg and Ca modification behavior were discussed. [ABSTRACT FROM AUTHOR]

The effect of large plastic deformations at room temperature in a Bridgman anvil cell on the specific saturation magnetization of the DO3-type ordered (Fe-24 at % Al) alloy has been revealed. It has been found that torsion at high pressure and certain deformation parameters results in the complete suppression of long-range order in the alloy and in the corresponding increase in the specific saturation magnetization by 11% with respect to the equilibrium state. A theoretical model qualitatively describing the revealed phenomenon has been proposed. [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]

The thickness of the intermetallic compound (IMC) layer that forms when aluminum is welded to steel is critical in determining the properties of the dissimilar joints. The IMC reaction layer typically consists of two phases ( η and θ) and many attempts have been made to determine the apparent activation energy for its growth, an essential parameter in developing any predictive model for layer thickness. However, even with alloys of similar composition, there is no agreement of the correct value of this activation energy. In the present work, the IMC layer growth has been characterized in detail for AA6111 aluminum to DC04 steel couples under isothermal annealing conditions. The samples were initially lightly ultrasonically welded to produce a metallic bond, and the structure and thickness of the layer were then characterized in detail, including tracking the evolution of composition and grain size in the IMC phases. A model developed previously for Al-Mg dissimilar welds was adapted to predict the coupled growth of the two phases in the layer, whilst accounting explicitly for grain boundary and lattice diffusion, and considering the influence of grain growth. It has been shown that the intermetallic layer has a submicron grain size, and grain boundary diffusion as well as grain growth plays a critical role in determining the thickening rate for both phases. The model was used to demonstrate how this explains the wide scatter in the apparent activation energies previously reported. From this, process maps were developed that show the relative importance of each diffusion path to layer growth as a function of temperature and time. [ABSTRACT FROM AUTHOR]

An innovative method for separating non-metallic inclusions from a high temperature melt using super gravity was systematically investigated. To explore the separation behavior of inclusion particles with densities less than that of metal liquid under a super-gravity field, a Fe-Al-O melt containing AlO particles was treated with different gravity coefficients. AlO particles migrated rapidly towards the reverse direction of the super gravity and gathered in the upper region of the sample. It was hard to find any inclusion particles with sizes greater than 2 μm in the middle and bottom areas. Additionally, the oxygen content in the middle region of the sample could be reduced to 0.0022 mass pct and the maximum removal rate of the oxygen content reached 61.4 pct. The convection in the melt along the direction of the super gravity was not generated by the super-gravity field, and the fluid velocity in the molten melt consisted only of the rotating tangential velocity. Moreover, the motion behavior of the AlO particles was approximatively determined by Stokes' law along the direction of super gravity. [ABSTRACT FROM AUTHOR]

The effects of several variables on the precipitation of the β-AlFeSi phase, and porosity formation in A319.2 alloys were examined in detail. Various techniques were used for microstructural characterization and phase identification, including optical and scanning electron microscopy, electron probe microanalysis coupled with energy-dispersive X-ray and wavelength-dispersive spectroscopy facilities, and thermal analysis. An image analyzer was used in conjunction with the optical microscope for quantification purposes. The results obtained showed that the amount of iron present in the alloy affects the size of the β-AlFeSi platelets and their distribution, particularly at low solidification rates. Addition of strontium leads to fragmentation of co-eutectic or post-eutectic β-platelets. This effect diminishes with the increase in iron concentration, and further strontium addition leads to the precipitation of AlSiSr phase particles, instead. The porosity observed at any given iron level is the result of the competition between fluidity and β-platelet size and depends on the permeability of the interdendritic regions as solidification proceeds. Although branching of the β-platelets leads to porosity formation, the platelets, on the other hand, also limit pore growth. In general, percentage porosity, maximum pore area and maximum pore length increase with an increase in the average maximum β-AlFeSi platelet length. In the Sr-modified alloys, porosity formation is frequently associated with strontium oxides (particles or films), as well as the β-AlFeSi platelets. These oxides (with a stoichiometric composition close to AlSrO) are formed during melting, due to the high oxygen affinity of strontium, and are difficult to remove via degassing. [ABSTRACT FROM AUTHOR]

A new grain refiner, LaB, was identified for ferritic steels based on the crystallographic calculation using the edge-to-edge matching model. Addition of 0.5 wt pct LaB led to a reduction of the average grain size from 765 to 92 μm and the proportion of the columnar structure from 35 to 8 pct in an as-cast Fe-4Si ferritic alloy. Although LaB was supposed to act as an active inoculant for δ-ferrite, thermodynamic calculation indicated that LaB is not thermodynamically stable in the melt of the Fe-4Si alloy. It was subject to decompose into La and B solutes. Consequently, both La and B reacted with Fe, O and S, forming different compounds. Microstructural examination at room temperature observed LaSO and LaO particles within the ferrite grains and FeB along the grain boundaries in the samples. Through EBSD analysis, a reproducible orientation relationship between ferrite and LaSO was identified. In addition, the edge-to-edge matching calculation also predicted the high potency for LaSO to be an effective nucleant for δ-ferrite. It was considered that the grain refinement of LaB was attributed to the enhanced heterogeneous nucleation of δ-ferrite by LaSO, and the solute effect of B due to the high Q-value in ferrite. [ABSTRACT FROM AUTHOR]

In the present work, the ternary system Fe-Al-Nb was modeled with the Calphad approach based on new experimental data including the invariant reaction scheme, liquidus surface, and isothermal sections. In order to get a reasonable description for the ternary system, the Fe-Nb binary system had to be updated to improve the description of the C14 Laves phase. Recent experimental results on the solvus of the C14 phase as well as new ab initio data were taken into account together with all other available experimental information. A complete thermodynamic description of the Fe-Al-Nb system is obtained, and extensive comparisons between calculated and experimental data are presented showing that almost all the available experimental and theoretical data are satisfactorily fitted. [ABSTRACT FROM AUTHOR]

The aim of works was to describe mathematically the kinetics of static recrystallization of the alloy type Fe–40 at.%Al–Zr–B (with 24.6 Al–0.01 B–0.18 Zr–0.01 C in wt.%) with the coarse-grained structure. The microstructure of the laboratory castings made of this extremely brittle alloy was homogenized by hot rolling of the material in the protective capsules and by the long-term annealing at 1200 °C. An initial microstructure with average grain size 0.77 ± 0.27 mm was obtained. Based on the isothermal plastic deformation tests and EBSD analysis, the static recrystallization kinetics of the prepared coarse-grained B2 iron aluminide after strain 0.20 was mathematically described. Recrystallized fraction depends on deformation/annealing temperature (900–1100 °C) as well as on annealing time. The activation energy of static recrystallization was calculated as 255 kJ mol −1 . Competition between dynamic recovery and static recrystallization was proved after strain 0.35 and annealing temperature 1100 °C. Static recrystallization starts relatively easily in the studied alloy, but a very long-term annealing is quite necessary for the complete course of recrystallization. The mean size of recrystallized grains falls with the decreasing annealing temperature (0.47 ± 0.15 mm for temperature 1100 °C, and 0.22 ± 0.04 mm for 900 °C). Even at a temperature of 1200 °C the annealing after deformation should last approx. 1 min for obtaining the fully recrystallized microstructure. That is why the standard hot forming technologies should be combined by an interpass annealing in order to refine sufficiently the coarse grains. [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]

The compressive yield stress of Fe-26Al with additives Ti (0.5 to 4 at. pct), Cr (0.5 to 8 at. pct), Mo (0.5 to 4 at. pct), and V (0.5 to 8 at. pct) at 1073 K (800 °C) has been determined. The effect of the concentration of diverse solutes on the yield stress at 1073 K (800 °C) was compared, and the additivity of the effects of solutes was tested. The effects in iron aluminides with two solutes (V and Ti, Ti and Cr, V and Cr) are compared with those of a single solute V, Ti, and Cr. It is found that the additivity of yield stress increments is valid only for lower solute concentrations. When the amount of the solute atoms increases, the yield stress increment is substantially higher than the sum of the yield stress increments of single solutes. This behavior is related to the high-temperature order in iron aluminides. [ABSTRACT FROM AUTHOR]

The interfacial contact in exothermically reacting mixture of Fe and Al powders (or Al-alloy) designed for the formation of intermetallic FeAl powder is studied by differential thermal analysis (DTA). The effect of alloying elements such as Mg and Ti on this process is analyzed. The behavior of the Fe-Al-based powder produced by heating under DTA conditions is compared with that of the powder with the same composition produced by mechanochemical synthesis. [ABSTRACT FROM AUTHOR]

Al-Mg-Fe alloys are appointed as favorable ones with respect to the costs and all the required properties for successful vessel service. However, the experimental inter-relations of solidification thermal parameters, microstructure, and mechanical strength are still undetermined. In the present research work, the dependences of tensile properties on the length scale of the dendritic morphology of ternary Al-1.2 wt pct Mg-1.5 wt pct Fe and Al-7 wt pct Mg-1.5 wt pct Fe alloys are examined. Transient heat flow conditions during solidification have been achieved by the use of a directional solidification system, thus permitting a comprehensive characterization of the dendritic microstructures to be performed. Thermo-Calc computations, X-ray diffraction, and scanning electron microscopy analyses are carried out to give support to the extensive microstructural evaluation performed with both ternary Al-Mg-Fe alloys. Experimental growth relations of primary, λ , and secondary, λ , dendrite arm spacings with cooling rate ( $$ {\dot T}_{\rm{L}} $$ ) and of tensile properties with λ are proposed. For both alloys examined, Hall-Petch type formulas show that the tensile strength increases with the decrease in λ . The soundest strength-ductility balance is exhibited by the Al-7 wt pct Mg-1.5 wt pct Fe alloy specimen with refined microstructure. This is shown to be due to a more homogeneous distribution of intermetallic particles in connection with solid solution strengthening propitiated by Mg. Functional experimental inter-relations of tensile properties with growth ( V ) and cooling rates ( $$ {\dot T}_{\rm{L}} $$ ) for both ternary Al-Mg-Fe alloys have also been derived. [ABSTRACT FROM AUTHOR]

Samples of Fe-Al-C alloys of varying composition were synthesized under high pressures and temperatures. From X-ray analysis data, only K-phase with usual for it average parameter of elemental lattice cell, a = 0.376 nm, carbide FeC and cubic diamond reflexes were present before and after cooling to the temperature of liquid nitrogen. Calculations were made of the parameters of unit cells, the enthalpy of formation of the FeAlC, FeAlC, FeAlC, FeAlC, FeAlC, and FeAlC unit cells and crystallographic planes were identified on which epitaxial growth of the diamond phase was possible, using density functional theory as implemented in the WIEN2k package. The possibility of epitaxial growth of diamond crystals on FeAlC (K-phase) nanoparticles was, therefore, demonstrated. The [200] plane was established to be the most suitable plane for diamond growth, having four carbon atoms arranged in a square and a central vacancy which can be occupied by carbon during thermal-and-pressure treatment. Distances between carbon atoms in the [200] plane differ by only 5% from distances between the carbon atoms of a diamond. The electronic structure and energetic parameters of the substrate were also investigated. It was shown that the substrate with at least four intermediate layers of K-phase exhibits signs of stability such as negative enthalpy of formation and the Fermi level falling to minimum densities of states. [ABSTRACT FROM AUTHOR]

Tri-axial plane-strain forging was applied to the Fe-28Al-5Cr-0.8Zr-0.04B intermetallic alloy, in order to study its grain refinement and possible improvement in mechanical properties. The forging temperature range was from 20 to 600 °C. The maximum number of forging passes was 67. The deformed microstructure was investigated using electron backscatter diffraction in a scanning electron microscope. At forging temperatures <500 °C, the alloy was very prone to brittle cracking. At the temperature range of 500-600 °C, the overall plasticity of material increased and the cracking tendency was reduced but not completely eliminated. Extensive processes of dynamic recovery/recrystallization were observed during forging at 600 °C after 10-40 passes. Recrystallized areas with an average grain size of a few micrometers were observed. However, even after severe deformation at 600 °C, resulting from 40 forging passes ( ε ~ 11.3), dynamic recrystallization was incomplete and the fraction of low-angle boundaries was still high. The Vickers microhardness substantially increased from 280 HV0.1 to 450 HV0.1 at the center of the sample after both deformations at room temperature as well as after 20-40 cycles at 500-600 °C. However, a further increase of strain for a sample deformed at 600 °C after 67 passes ( ε ~ 28) led to quite a significant hardness decrease at the center of the sample. This phenomenon could be associated with the initiation of dynamic recrystallization. None of the samples forged at the 500-600 °C range exhibited any ductility improvement during subsequent tensile testing at room temperature, most likely, owing to the absence of a uniform ultrafine-grained structure developed during forging. [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]

Iron aluminides containing carbon are promising materials for tribological applications. Because of graphite formation at higher ( >20 wt%) Al-contents the addition of carbon to FeAl-based alloys has not been successful. The graphite precipitation may be avoided by addition of Zr or Ti. Dry sliding wear behaviour of FeAl-based alloys containing 1-1.5 wt% carbon with quaternary addition of Ti or Zr has been studied using ball-on-disk wear test. Effect of sliding speeds and applied loads is investigated and correlated with mechanical properties. Wear resistance of FeAl-based alloys is found to be significantly improved on addition of Ti /Zr. This is attributed to the high hardness of alloy carbides. The lower load-bearing capacity of graphite flakes in localized region was found to increase the wear rate of the alloy. The carbides such as Fe AlC , TiC and ZrC are embedded in the matrix after sliding wear without destruction or delamination. This significantly affects the wear resistance of FeAl-based alloys. [ABSTRACT FROM AUTHOR]

Creep experiments were conducted on Fe-25 at. pct Al-5 at. pct Zr alloy with carbon additions at the temperatures of 973 K and 1173 K (700 °C and 900 °C). The alloys were tested in two different states: (i) cast and (ii) annealed at 1273 K (1000 °C) for 50 hours. Stress exponents and activation energies were estimated. The values of the stress exponent n could be explained by the dislocation motion controlled by climb. The increased values of n in the high-carbon alloy at the temperature of 1173 K (900 °C) can be described by means of the threshold stress concept. The creep resistance at 973 K (700 °C) decreased with the increasing content of carbon. This result is discussed in terms of the ratio of zirconium to carbon in the alloy. An increase of the creep resistance with increasing ratio Zr:C is in agreement with the behavior observed previously in alloys with substantially lower concentrations of zirconium. [ABSTRACT FROM AUTHOR]

This study showed that MgO inclusions can be stable in liquid iron with elevated Al and it illustrated an important role of vaporization in the evolution of inclusions. Previous studies have shown that dissolved Al reduces MgO from slags and refractories, leading to spinel (MgAlO) inclusions. The elevated Al content of newer steels raises the possibility that MgO inclusions can be stable. In this work, MgO inclusions were produced and observed in an Fe-Al alloy. The inclusions in the liquid alloy at 1873 K (1600 °C) were observed in situ with a Confocal Laser Scanning Microscope (CLSM). Two types of experiments were performed: one where only a metal sample was melted and the other where the sample was in contact with a liquid, MgO-saturated slag. When no slag was present, the MgO inclusions shrank and disappeared at 1873 K (1600 °C). No inclusions were observed in situ during cooling or in post-CLSM analysis. When the MgO-saturated slag was present, the inclusion sizes were essentially constant and MgO was observed on the surface of post-CLSM samples. Analysis of the results showed that MgO can be stable in 1873 K (1600 °C), but that its presence depends on the rate of removal of Mg due to vaporization and the supply of Mg due to slag/metal or refractory/metal reactions. [ABSTRACT FROM AUTHOR]

Three-layer YO, CeO, SiO-AlO and SiO-AlO-YO-CeO coatings were deposited by sol-gel method on the FeCrAl alloy foil substrate. The protective properties of the coatings during high-temperature cyclic oxidation and the changes in the topography of the surface, the structure, and chemical composition of the FeCrAl alloy surface layer were examined. It has been shown that small additions of cerium and yttrium affect the morphology of the growing AlO scale. After 10 oxidation cycles in air ( T = 900 °C, t = 120 h, one cycle = 12 h), the smallest change in the mass of the samples was observed for YO and SiO-AlO-YO-CeO coatings with an appropriate yttrium and cerium content. The protection effectiveness of the coatings to that of uncoated substrate after 10 oxidation cycles ranges from 28 to 66 %. The oxidation scale thickness ( h) and the designated value of the parabolic rate constant ( k ) depended on the yttrium and cerium content in the coating. [ABSTRACT FROM AUTHOR]

A correction to the article "Thermodynamic Modeling of the Fe-Mn-C and the Fe-Mn-Al Systems Using the Modified Quasichemical Model for Liquid Phase" in the 2015 issue is presented.

The slab reheating process of binary iron-aluminum alloys and an industrial TRIP steel grade has been investigated in both dry and wet atmospheres. The presence of water vapor has a significant effect on the overall scale growth and internal corrosion depth. Heating rate greatly influences the porosity of the surface oxide layer with the surface getting more porous at faster heating rates. Nitride formation could be suppressed in the presence of water vapor, leading to a reduction of internal corrosion depth and a better formability of the final material. Experimental results were compared to thermodynamic predictions and critically discussed. [ABSTRACT FROM AUTHOR]

Many of the aluminum casting alloys used today are based on the aluminum-silicon eutectic system, because it imparts excellent casting ability to the alloys. However, the high temperature strength of these alloys is limited. Therefore, it is desirable to find alternate eutectic systems that would become the basis for a new generation of aluminum casting alloys that possess higher strength at room and elevated temperatures. In this study, the aluminumnickel, aluminum-iron and aluminum-iron-nickel eutectic systems are presented as potential alternatives to the aluminum- silicon eutectic system for constituting aluminum casting alloys. The casting ability and tensile properties at room and elevated [350 °C (662 °F)[ temperatures were measured and compared to those of the aluminum-silicon eutectic. The casting ability and room temperature tensile properties of the alternative eutectics were found to be competitive with those of the aluminum-silicon eutectic, while the alternative eutectic systems have a significant advantage in elevated temperature tensile strength. [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]

The effect of characteristics of non-metallic inclusions in Fe-Al-Ti-O-N-S alloys with various compositions at 1473 K (1200 °C) on the microstructure was studied. The ASTM grain size number was determined in as-cast and heated samples by the optical microscopy, and the inclusion types in each sample were determined from composition analysis by field-emission scanning electron microscope with energy-dispersive spectroscopy. The TiN-based inclusions certainly had a positive effect on the grain refinement. On the other hand, TiS-based inclusions exhibited no influence on the decrease of grain size. In addition, the formation and evolution behavior of inclusions by heating solid-state Fe-Al-Ti-O-N-S alloys with those locations were clarified. A different change of inclusions in alloys was observed depending on the distribution and composition of inclusions. [ABSTRACT FROM AUTHOR]

Powders of the FeAl melted and heat treated samples were separated at different mean particle sizes as well as characterized based on their structural and magnetic properties. All the samples, except that with biggest particle size, showed Fe-Al BCC and α-Fe phases as well as the same nanostructure. The powder with the biggest particles, with particle size bigger than 105 μm, presents the additional minority presence of FeO and AlO phases. The powders were found to be ferromagnetic at room temperature with a mean hyperfine magnetic field (MHMF) that increases with increasing particle size. The origin of the increase of the MHMF is attributed to the increment of the magnetic dipolar interactions between the magnetic moment of each particle and the field produced by other magnetic moments of their surrounded particles. This field also increases as the particle size increases. Besides the dipolar magnetic interaction between particles, the Fe-Al and α-Fe grains present a ferromagnetic coupling between them. [ABSTRACT FROM AUTHOR]

In order to successfully establish vegetation on bauxite residue, properties such as aggregate structure and stability require improvement. Spontaneous plant colonization on the deposits in Central China over the last 20 years has revealed that natural processes may improve the physical condition of bauxite residues. Samples from three different stacking ages were selected to determine aggregate formation and stability and its relationship with iron-aluminium oxides and organic carbon. The residue aggregate particles became coarser in both dry and wet sieving processes. The mean weight diameter (MWD) and geometry mean diameter (GMD) increased significantly, and the proportion of aggregate destruction (PAD) decreased. Natural stacking processes could increase aggregate stability and erosion resistant of bauxite residues. Free iron oxides and amorphous aluminium oxides were the major forms in bauxite residues, but there was no significant correlation between the iron-aluminium oxides and aggregate stability. Aromatic-C, alkanes-C, aliphatic-C and alkenes-C were the major functional groups present in the residues. With increasing stacking age, total organic carbon content and aggregate-associated organic carbon both increased. Alkanes-C, aliphatic-C and alkenes-C increased and were mainly distributed in macro-aggregates, whereas aromatic-C was mainly distributed in <0.05-mm aggregates. Organic carbon stability in micro-aggregates was higher than that in macro-aggregates and became more stable. Organic carbon contents in total residues, and within different aggregate sizes, were all negatively correlated with PAD. It indicated that organic materials had a more significant effect on macro-aggregate stability and the effects of iron-aluminium oxides maybe more important for stability of micro-aggregates. [ABSTRACT FROM AUTHOR]

The Al-rich part of the Fe-Al phase diagram between 50 and 80 at.% Al including the complex intermetallic phases FeAl (ε), FeAl, FeAl, and FeAl was re-investigated in detail. A series of 19 alloys was produced and heat-treated at temperatures in the range from 600 to 1100 °C for up to 5000 h. The obtained data were further complemented by results from a number of diffusion couples, which helped to determine the homogeneity ranges of the phases FeAl, FeAl, and FeAl. All microstructures were inspected by scanning electron microscopy (SEM), and chemical compositions of the equilibrium phases as well as of the alloys were obtained by electron probe microanalysis (EPMA). Crystal structures and the variation of the lattice parameters were studied by x-ray diffraction (XRD) and differential thermal analysis (DTA) was applied to measure all types of transition temperatures. From these results, a revised version of the Al-rich part of the phase diagram was constructed. [ABSTRACT FROM AUTHOR]

The spallation behaviour of alumina scales grown on FeCrAlY alloy was investigated. Substrates with different thicknesses were oxidized at 1200 °C for 25 h and cooled at various cooling rates. Generally, the scale formed on a thicker substrate or with a faster cooling rate exhibits a larger compressive stress. However, the failure behaviour of alumina scales is more complicated than expected for a compressed film. Specifically, (i) the extent of the spallation is not proportional to the residual stress in the oxide; (ii) the spallation does not occur immediately after cooling, but requires a period of incubation. This indicates that the residual stress is not the sole reason for the failure of scales. It was found that the carbide forms at the oxide-metal interface after cooling, which acts in conjunction with the residual stress to control the spallation of oxides. In addition, the mechanics analysis suggests that the microscopic roughness at the interface is another important factor. [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]

Ab initio investigations of the structural, electronic, and thermoelectric properties of stoichiometric FeVAl full-Heusler alloy and FeVMAl (M = Mo, Nb, Ta) nonstoichiometric alloys have been performed using density functional theory on the basis of the full-potential linearized augmented plane wave method with the generalized gradient approximation. The thermoelectric properties are calculated using semiclassical Boltzmann transport theory within the constant-relaxation-time approximation. FeVAl, FeVNbAl, and FeVTaAl alloys are found to exhibit a semimetallic behavior, while FeVMoAl acts as a metal. We found that FeVAl has a pseudogap of about −0.13 eV, whereas FeVNbAl and FeVTaAl are characterized by a zero energy gap around the Fermi level. Thermoelectric calculations showed that FeVAl has both p- and n-type thermoelectric properties, where the p-type thermopower values are found to be higher than those of n-type. The Seebeck coefficient S has maximum values from 20 μV K to 125 μV K and from 19 μV K to 90 μV K in the temperature range of 100 K to 800 K for p- and n-type, respectively. The maximum thermoelectric properties can be obtained at carrier concentration of the order of 10 cm for p- or n-type doping. Substitution of Nb and Ta atoms enhanced the thermoelectric properties to 150 μV K at 800 K. The optimum concentrations for the three partially substituted alloys were found to be between 10 cm and 10 cm. [ABSTRACT FROM AUTHOR]

The electronic properties of the typical Heusler compound CoFeAl with chalcogenide element doping were investigated by means of first principles calculations within the local spin-density approximation (LSDA) + Hubbard U parameter (U). The calculations indicate that, only when 25% of the number of Al atoms is substituted by the chalcogenide element, the chalcogenide element-doped CoFeAl shows the half metallic properties. The Fermi energy ( E) of the 25% chalcogenide element-doped CoFeAl is located in the middle of the gap of the minority states instead of around the top of the valence band as in CoFeAl. Moreover, the band gap of 25% Te-doped CoFeAl (0.80 eV) is wider than that of CoFeAl (0.74 eV). These improved electronic structures will make 25% chalcogenide element-doped CoFeAl more stable␣against temperature variation. Therefore, the expected excellent stability of the 25% chalcogenide element-doped CoFeAl make it more suitable␣for spintronic applications than CoFeAl. [ABSTRACT FROM AUTHOR]

Two types of multilayer structure with high magnetic shield effectiveness are presented experimentally and theoretically. Aluminized coatings were deposited on the two sides of pure iron substrate by using hot dip aluminizing. After diffusion heat treatment, iron-aluminum multilayer composite was obtained with Fe-Al alloy/Fe/Fe-Al alloy structure, which could be seen as three permeable magnetic layers in macro scale. A spacer was inserted between a couple of iron-aluminum multilayer composite plates to form sandwich structure with permeable magnetic layer/non-magnetizer/permeable magnetic layer structure. The results indicate that good bonding exists between the pure iron substrate and the Fe-Al reaction layer with a clean and flat interface after heat treatment. Geomagnetic shielding factor (SF) of iron-aluminum multilayer composite arrives at 25.5, which is about 7.7 times of pure iron substrate. The value of SF for sandwich structure can reach 210, about 8.2 times as high as for the multilayer composite magnetizer. Mathematical equation of SF for multilayer composite and sandwich structure are derived according to magnetic reluctance and magnetic circuit method. The three permeable magnetic layers in multilayer composite shunt the magnetic field in parallel and the sandwich structure can shunt magnetic field twice to achieve excellent shielding effectiveness. The theoretical computational results of SF agree well with the experimental values. [ABSTRACT FROM AUTHOR]

Thermodynamic modeling of Fe-Mn-C and Fe-Mn-Al ternary systems was performed in order to develop a thermodynamically consistent database of a Fe-Mn-Al-C quaternary system. The system is a core system of high Mn-high Al steels for various applications including automotive, cryogenic, electrical steels, etc., and ferromanganese alloy production. Most previous thermodynamic modeling results were reviewed. In order to treat strong chemical interaction between metals (Fe and Mn) and non-metal (C), the modified quasichemical model in the pair approximation was employed for the liquid phase. A number of solid solutions were modeled using the compound energy formalism. Gibbs energy descriptions in sub-binary systems were taken from previous literatures, except for the Mn-Al binary system. Liquid phase in the Mn-Al system was re-optimized in the present study, while the model parameters for other solid phases were adopted from a literature. By merging the Gibbs energies for relevant phases in sub-binary systems, thermodynamic calculations were carried out for each ternary system. Optimization results of the Fe-Mn-C system in the present study showed improved descriptions for both liquid and solid phases. Solubilities of C in the liquid and the fcc phases were reproduced well, and phase diagram information (liquidus, invariant reactions) was also in good agreement with the experimental data. Thermodynamic assessment of the Fe-Mn-Al system with consideration of A2/B2 order-disorder transition for the bcc phase also showed satisfactory representations for the experimental data. The model parameters derived in the present study can be utilized for further thermodynamic modeling of the Fe-Mn-Al-C quaternary system. [ABSTRACT FROM AUTHOR]

Using the first-principles calculations based on density functional theory within the generalized gradient approximation (GGA), we investigate the structural, electronic and magnetic properties of the TiZAl (Z = Co, Fe, Mn) alloys with the CuHgTi-type structure. The optimized equilibrium lattice constants were found to be 6.08 Å for TiCoAl, 6.07 Å for TiFeAl and 6.16 Å for TiMnAl. The TiZAl (Z = Co, Fe, Mn) alloys are found to be half-metallic ferromagnets. The total magnetic moment of TiZAl (Z = Co, Fe, Mn) is 2, 1 and 0 µ, respectively, which is in agreement with the Slater-Pauling rule M= Z- 18. The TiZAl (Z = Co, Fe, Mn) have a band gap of 0.64745, 0.57795 and 0.39327 eV, respectively. [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]

Arc spraying of Fe-Al-based coatings is widely used in for remanufacturing and other requirements due to its high performance; however, the bond strength between coating and substrate is about 50 MPa, so the changes therein are important in the cutting process. Moreover, such coatings are thin, and their surface is coarse, so this predefines two cutting steps in any subsequent machining process. It indicates that three factors affect the bond strength including the following: machine tool natural vibration, cutting tool regenerative vibration, and forced vibration due to the rough surface. This work presents a spindle-tool-workpiece vibration model of the coating machining process and studies the effects of transient cutting force, residual stress, and cutting parameters on the bond strength. The results show that the transient maximum influence of cutting force on the bond strength is 7.27 MPa, and the residual stress affects the material to a depth of 1.6 mm. Then, a bond strength calculation model was obtained to calculate the bond strength reduction as induced by choice of cutting parameters. The calculation model was verified experimentally, and it was shown that cutting depth was the main factor affecting bond strength. Combined with SEM inspection, this work showed that the interface gap was amplified during cutting. Importantly, to achieve the necessary bond strength, the first cutting depth should be less than 0.1 mm (allowing for the surface dimensional difference), and the cutting depth of other cutting steps should be less than 0.2 mm; in addition, the finishing coating thickness should be more than 0.2 mm. [ABSTRACT FROM AUTHOR]

We have studied superparamagnetic magnetites with various isomorphous aluminum contents, identified the cation distribution in their structure, and demonstrated nonlinear variations in their unit cell parameter and density and also a nonlinear variation in their magnetization, with a maximum at an aluminum content of 3.6% ( x = 0.3). The conclusion has been made that the properties of the superparamagnetic magnetites with isomorphous aluminum can be used in optimizing the composition of nanocomposite materials with tailored magnetic properties. [ABSTRACT FROM AUTHOR]

In order to provide accurate information for refining of steel containing more than 1 mass pct Al, previously known information about Al deoxidation equilibria in liquid iron was critically reviewed. New Al deoxidation equilibria, Al and O contents in liquid iron in equilibrium with solid AlO were measured at 1873 K and 1923 K (1600 °C and 1650 °C) over the whole Al composition range, 0.0027 < [pct Al] < 100. In order to secure the deoxidation equilibria, in the present study, the Al deoxidation experiments were carried out by employing three different methods: (1) traditional Al deoxidation by the addition of Al into Fe-O alloys, (2) oxidation of Al in Fe-Al alloys by the addition of FeO as an oxygen source, and (3) addition of CaO flux for an effective removal of suspended AlO inclusions in liquid alloys containing high Al. In addition, in the present study, the O solubility limit in pure Al melt in equilibrium with solid AlO was also measured in the temperature range from 1673 K to 1873 K (1400 °C to 1600 °C). The present experimental results provide a complete set of Al deoxidation equilibria in liquid iron which may be useful for the estimation of residual oxygen level and alumina inclusion formation in high Al steel processing. Interaction parameter formalism, which was originally proposed by Wagner and Chipman and has been widely used to interpret the Al deoxidation equilibria in liquid iron, was found to be inapplicable. Limitation of the interaction parameter formalism at high Al content in liquid Fe was discussed. [ABSTRACT FROM AUTHOR]

The arc-spraying Fe-Al-based coating cutting process is a spindle-tool-workpiece vibration system dependent upon the machine tool's dynamic performance, cutting tool vibration, the coarse coating surface and its thin cutting depth. To investigate the cutting force, this research indicates the coating cutting fundamental mechanics; furthermore, it represents two cutting steps and cutting force models in the machining process avoiding an analysis of the natural vibration parameters of the machine tool itself. In the first cutting step, there is a transient cutting force due to forced vibration of the rough surface; the second cutting step has a steady machining feature based on the first cutting surface and the reduced hardness of the inhomogeneous region. According to the different characteristics of each cutting step, this research presents dynamic cutting calculation models including cutting parameters, tool vibration and cutting depth effects in the first cutting step. A steady cutting model is based on three cutting parameters including cutting velocity, cutting feed and cutting depth. Piezoelectric force and acceleration sensors were used to obtain accurate experimental data. Then, response surface methodology (RSM) and the principle of least squares estimation of polynomial regression (PLSEPR) were applied to analyse the resultant cutting data. The results showed that cutting force calculation models were suitable for the coating machining. [ABSTRACT FROM AUTHOR]