FeAl Phase Research Articles

Interface Microstructure and Mechanical Properties of Al/Steel Bimetallic Composites Fabricated by Liquid-Solid Casting with Rare Earth Eu Additions.

To improve the Al/Steel bimetallic interface, Eu was firstly added to the Al/Steel bimetallic interface made by liquid-solid casting. The effects of Eu addition on the microstructure, mechanical capacities, and rupture behavior of the Al/Steel bimetallic interface was studied in detail. As the addition of 0.1 wt.% Eu, the morphology of eutectic Si changed from coarse plate-like to fine fibrous and granular in Al-Si alloys, and the average thickness of the intermetallic compounds layer decreased to a minimum value of 7.96 μm. In addition, there was a more sudden drop of Fe in steel side and the Si in Al side was observed to be more than the other conditions. The addition of Eu did not change the kinds of intermetallic compounds in the Al/steel reaction layer, which was composed of Al5Fe2, τ1-(Al, Si)5Fe3, Al13Fe4, τ5-Al7Fe2Si, and τ6-Al9Fe2Si2 phases. The addition of the element Eu did not change the preferential orientation of the Al5Fe2, τ1-(Al, Si)5Fe3, Al13Fe4, τ5-Al7Fe2Si, and τ6-Al9Fe2Si2 phases, but refined the grain size of each phase and decreased the polar density of Al5Fe2 phase. Eu was mainly enriched in the front of the ternary compound layer (τ6-Al9Fe2Si2) near the Al side and steel matrix. The Fe and Al element distribution area tended to narrow in the interface after the addition of 0.1 wt.% Eu, which is probably because that Eu inhibits the spread of Al atoms along the c-axis direction of the Al5Fe2 phase and the growth of Al13Fe4, τ5-Al7Fe2Si, and τ6-Al9Fe2Si2 phases. When the Eu content was 0.1 wt.%, the shear strength of the Al/Steel bimetal achieved a maximum of 31.21 MPa, which was 47% higher than the bimetal without Eu.

Controllable tensile performance of additively manufactured Al–Fe alloy

Achieving both high strength and ductility is challenging in additive manufacturing of Al alloys using the laser powder bed fusion (L-PBF) process by altering the laser conditions to control the microstructural characteristics. The current work focuses on the influence of varying laser energy density (ED), which is adjusted by different sets of laser power (P) and scan speed (v), on the microstructure-tensile property relationships of the L-PBF-fabricated Al–2.5%Fe alloy under varying laser conditions (P = 204–230 W, v = 450–600 mm/s) with a fixed powder layer thickness (t = 30 μm) and hatch distance (h = 30 μm). With increasing ED (= P/v·t·h), a slight increase in the average size of the columnar α-Al grains was found in the experimental samples concurrently with a higher fraction of <001>-oriented grains. Nanosized particles of the Al6Fe phase with an increased tendency to interconnect were observed in the matrix inside the melt pool, and the θ phase formed within the submicron-sized cellular structure along the melt pool boundaries (MPBs). A low tensile ductility, induced by the local microstructural inhomogeneities across MPBs, was found in all specimens tensile-deformed along the building direction, which was characterized by a preference fracture along the MPBs. At higher applied ED, the tensile ductility of the experimental Al–2.5Fe alloy was significantly improved with only a slight decrease in tensile strength. The difference in concentration of Fe across the MPBs in the matrix was also moderately diminished, which is consistent with the reduced local difference in microhardness across the MPBs under higher ED conditions. Therefore, the present results demonstrate that local microstructural inhomogeneities across MPBs can be controlled by the laser conditions, thereby producing both high strength and good ductility in the L-PBF processed Al–Fe alloys.

Influence of the second phase on relative fracture behavior of friction stir welded 7A52 aluminum alloy

The mechanical properties of welded joints play a decisive role in service life of the materials, and the second phase particles significantly affect the fracture behavior of the welded joint. In present work, 7A52 aluminum alloy welded joints were prepared by friction stir welding (FSW), the morphologies of different second phases distributed in the joints were observed by SEM, TEM, EBSD and the fracture behavior of the advance side was investigated by in-situ tensile testing. The results show that the fracture is located at the thermo-mechanically affected zone of advance side, where are serious crystal mutation and second phase segregation. Because of poor mechanical properties of the incoherent Mg2Si phase, the cracking initiated at the interface and showed a characteristic with multi-directional cracking. The incoherent AlFe phase cracked along the direction of shear force, and the separated phase interface provided the main cracking propagation path, which would reduce the energy consumption in the process of cracking propagation and accelerate the propagation speed. The semi-coherent AlMgCu phase with excellent mechanical properties hindered the movement of dislocations and improved the mechanical properties of the joints.

(Fe,Mn)3AlCx κ-carbide formation and characterization in pack aluminization of Fe–29Mn–9Al–0.9C lightweight steel

The Fe–Mn–Al–C lightweight steel has been widely studied due to its higher strength-to-weight ratio and potential applications for automotive vehicles, energy, transportation and mining industries. In general, the strength and ductility of the Fe–Mn–Al–C lightweight steel can be improved by the formation of nano-sized (Fe,Mn)3AlCx κ-carbide precipitates by a proper heat treatment below 800 °C. In this work, a unique micrometer scale κ-carbide phase transformation phenomenon induced by the pack aluminization in the Fe–29Mn–9Al–0.9C lightweight steel was firstly reported.Extremely large columnar-like (Fe,Mn)3AlCx κ-carbide grains with average length of 18.1 μm embedded in the Fe3Al matrix were discovered in the interdiffusion zone of aluminization layer, which were totally different from these nanoscale κ-carbides precipitated in the austenitic steel matrix. The increased Al content in the pack aluminide coating/substrate interface reduced the chemical potential of carbon and became the driving force for carbon diffusion toward the coating/substrate interface. Therefore, due to the extremely low solubility of carbon in the Fe3Al phase and the inward diffusion of carbon atoms, very long columnar-like (Fe,Mn)3AlCx κ-carbide phases were thus produced in the interdiffusion zone. The average chemical concentration of the κ-carbide was 43.9Fe–27.3Mn–20.3Al–8.5 C (in at.%). The average hardness, elastic modulus and the lattice parameter of κ-carbide were 8.8 ± 0.3 GPa, 285 ± 10 GPa and 0.3764 nm, respectively. This study provided detailed chemical compositions, hardness and elastic modulus of (Fe,Mn)3AlCx κ-carbide phase for better understanding the carbide precipitation and strengthening mechanism of Fe–Mn–Al–C lightweight steel.

Modification and refinement of Fe-containing phases, mechanical properties and strengthening mechanisms in Al–Fe alloys via Cr alloying and continuous rheo-extrusion

Given limited resources, it is necessary to increase the recycling of wasted aluminum alloy products. Due to the increase in Fe content during recycling, the formation of needle-, lath- and flake-shaped Fe-rich intermetallics reduces the mechanical properties of alloys. In this work, the effects of Cr addition on the microstructural evolution and mechanical properties of as-cast and rheo-extruded Al–1.5Fe (wt%) alloys were investigated. The results indicated that with increasing the Cr content from 0 wt% to 1.2 wt%, the average size of α-Al grains and Al13Fe4 phases first decreased and then increased. When the Cr content was 0.4 wt%, the refined microstructure was obtained; the optimized ultimate tensile strength, yield strength, and elongation of the as-cast alloy were 103.5 MPa, 60.2 MPa, and 36.2%, respectively. In addition, in the as-cast Al–1.5Fe–0.4Cr (wt%) alloy, Cr adsorption on the surface of Al13Fe4 phases was found, which caused the growth inhibition for Al13Fe4 phases. When the Cr content was larger than 0.8 wt%, the formation of coarse Al–Fe–Cr ternary phases resulted in the deterioration of mechanical properties. In order to further tailor the Al13Fe4 phases, the continuous rheo-extrusion of Al–1.5Fe(–0.4Cr) (wt%) alloy was performed. The rheo-extruded Al–1.5Fe–0.4Cr (wt%) alloy exhibited a superior combination of strength and ductility. The strengthening mechanisms induced by Cr addition were discussed. Grain boundary strengthening and dislocation strengthening were responsible for the enhancement in yield strength of the rheo-extruded alloy.

3D morphological evolution and growth mechanism of proeutectic FeAl3 phases formed at Al/Fe interface under different cooling rates

• The morphologies of proeutectic FeAl 3 ranging from faceted polygonal prism to non-faceted rods with radial branches can be controlled by increasing the cooling rate. • The crystallographic growth directions, facets and branching behaviors of diverse proeutectic FeAl 3 morphologies were quantitated effectively based on the reconstructed 3D structures. • At a higher cooling rate, twinning mechanism plays a leading role in the formation and growth of FeAl 3 . The 3D morphologies and growth mechanisms of proeutectic FeAl 3 at the Al/Fe interface under different cooling rates were studied by synchrotron X-ray tomography. With increasing cooling rate, FeAl 3 crystals developed from faceted polygonal prism, plates with flat surface, thin ribbon-like with periodic undulating surface to non-faceted rods with radial dendrites in cross section, indicating a gradual interface growth mode transition from two-dimensional layer growth to continuous growth. At a higher cooling rate, twinning mechanism plays a leading role in the formation and growth of FeAl 3 . A link between the morphologies, twinning and crystallographic structure was established based on quantitative analyses on the 3D structures.

Nanoscale Tribological Properties of Nanostructure Fe3Al and (Fe,Ti)3Al Compounds Fabricated by Spark Plasma Sintering Method

Nanostructured powder particles of Fe3Al and (Fe,Ti)3Al phases were produced using mechanical alloying. These intermetallic phases with a nearly complete density were consolidated by spark plasma sintering. The mechanical properties of the bulk samples, i.e., elasticity modulus, hardness, and plasticity index, and also their tribological behavior were investigated using nanoindentation and nano-scratch tests. It was found that both Fe3Al and (Fe,Ti)3Al phases can be synthesized after 30 h of high-energy ball milling. In addition, no phase evolution was observed after spark plasma sintering. An analysis of the atomic force microscope images obtained from the nanoindentation tests showed a higher elasticity modulus, higher hardness, and lower plasticity index due to the addition of Ti to the Fe3Al system. (Fe,Ti)3Al displayed better tribological properties as compared with Fe3Al. A smaller volume of the scratched line was clearly seen in the atomic force microscope images of the nanostructured (Fe,Ti)3Al compound.

Al13Fe4-Al Composites with Nanocrystalline Matrix Manufactured by Hot-Pressing of Milled Powders.

The paper describes composites with the matrix containing a nanocrystalline intermetallic Al13Fe4 phase and microcrystalline aluminium. Mechanically alloyed Al80Fe20 powder, containing a metastable nanocrystalline Al5Fe2 phase, was mixed with 20, 30, and 40 vol.% of Al powder and consolidated at 750 °C under the pressure of 7.7 GPa. During the consolidation, the metastable Al5Fe2 phase transformed into a nanocrystalline Al13Fe4 phase. In the bulk samples, Al13Fe4 areas were wrapped around by networking Al regions. The hardness of the Al13Fe4-Al composites was in the range of 4.52–5.50 GPa. The compressive strength of the Al13Fe4-30%Al and Al13Fe4-40%Al composites was 805 and 812 MPa, respectively, and it was considerably higher than that of the Al13Fe4-20%Al composite (538 MPa), which failed in the elastic region. The Al13Fe4-30%Al and Al13Fe4-40%Al composites, in contrast, showed some plasticity: namely, 1.5% and 9.1%, respectively. The density of the produced composites is in the range of 3.27–3.48 g/cm3 and decreases with the increase in the Al content.

Mechanical characterisation of laminated composite AISI 430/304 stainless steels with 1050 Al alloy interlayer

ABSTRACT In this study, multilayered metal composites of austenitic stainless steel (AISI 304) / aluminum alloy (AA 1050) / ferritic stainless steel (AISI 430) are investigated in rolled and heat-treated (350˚C for 24 h) forms comparatively. SEM analysis, tensile test, peel test, bending test, and Vickers microhardness measurement were applied to reveal the microstructural characterisation and mechanical properties of composites. The presence of Fe2Al5 and Fe4Al13 phases are detected in the microstructure investigations, however, significantly thick intermetallic phases were not observed at the interfaces of the laminates. Tensile test results show no significant change in strength despite the increase in ductility after heat treatment. The highest strength of 329.4 MPa and the highest elongation of 26.1% is obtained from the heat-treated condition. The highest interface bond strength is observed at AA1050 / AISI 430 interface after heat treatment. No separation is observed between the layers after bending to a 60˚ angle. A decrease is observed in the hardness values of all layers with the heat treatment. Thus, it has been demonstrated how significant the heat treatment temperature and time, as well as the rolling temperature, are for better interface interaction and mechanical properties for layered composites.

Hot dip aluminization of 304L SS and P91 ferritic-martensitic steel – Comparison of interface morphology and growth kinetics of reaction zones

P91 ferritic/martensitic and AISI 304L austenitic stainless steels were hot dip aluminized (HDA) in 99.9% pure aluminum in a pit type vertical furnace at three different temperatures i.e. 750, 800 and 850 °C for 1 to 10 min. Evolution of interface morphology, type and distribution of phases and growth kinetics of the reaction zones were studied using a variety of experimental techniques. Though similar intermetallic compounds formed in both steels, their distribution, morphology and growth kinetics were distinctly different. In P91 F/M steel, aluminized surface adjacent to the substrate had wide Fe2Al5 layer with serrated morphology containing high volume fraction of 2–3 μm sized Cr rich intermetallic phases. Width of FeAl3 phase present adjacent to this layer did not show much variation with HDA conditions. Above FeAl3, on the surface, the pure Al top coat contained nonequilibrium phases. Compared to P91 steel, width of the aluminized layer in 304L SS was less (35 ± 5 μm vs 120 ± 15 μm at 800 °C-10 min) and the Fe2Al5 layer had a planar interface with the substrate. Optimum temperature-time combination to get thin, uniform, defect free surface aluminide layer in P91 F/M and 304L steels were found to be 750 °C-2 min and 800 °C-1 min respectively. Growth kinetics of surface aluminide layers in both steels were studied, kinetic parameters were determined and compared with information available in literature.

Effect of Rare Earth Ce on the Growth of Primary Al&lt;sub&gt;13&lt;/sub&gt;Fe&lt;sub&gt;4&lt;/sub&gt; Phase in Al-5Fe Alloy

The solid-liquid mixture of Al-5Fe-xRE alloy is "frozen" through rapid cooling technology to prepare solid samples (the weight percentage of Rare Earth Ce added in x: 0%, 0.9%, and 5%). The effect of Ce on the growth of primary Al13Fe4 phase is studied by means of differential scanning calorimetry (DSC) and field emission transmission electron microscopy (TEM).The results show that with the increase in the amount of Ce in the alloy, the transition temperature of the primary Al13Fe4 phase increases. The addition of Ce changes the crystallization process of the primary phase. When Al-5Fe-xRE alloy is rapidly cooled at 690°C, the primary phase interface of Al-5Fe-5Ce alloy has more Rare Earth enrichment than that of Al-5Fe-0.9Ce alloy. However, the primary phase of Al-5Fe-5Ce alloy is still relatively coarse. Obviously, excessive Ce does not play a role in modification, so the enrichment of Ce at the interface may not be the main reason for refining the primary iron-rich phase When the Al-5Fe-5Ce alloy is rapidly cooled at 750°C and 690°C, respectively, the Ce at the interface tends to increase. The enrichment area of Ce forms a "film" at the interface of the primary phase, and then it transform into Al8CeFe2 phase after solidification. The interface structure of the primary and Al8CeFe2 is semi-coherent.

Effect of Annealing and Oxidation on the Microstructure Evolution of Hot-Dipped Aluminide Q345 Steel with Silicon Addition

Q345 steel was coated by hot dipping into molten pure aluminum and Al-Si baths. The coatings were annealed at 800 and 900 °C for 1–3 h and subsequently oxidized at 900 °C for 15 h in air. The results revealed that the thickness of the intermetallic layer increased with increasing hot-dipping time in the range of 700–750 °C, while it decreased when the hot-dipping aluminizing temperature was 800 °C. As the silicon content in the aluminum bath increased, the thickness of the intermetallic layer decreased, and the intermetallic layer/steel-substrate interface transformed from an irregular morphology into a flat morphology. The hot-dipped Al-2.5Si samples were subjected to annealing; the higher the annealing temperature and longer the annealing time, the faster the transformation of the intermediate phase in the coating. The Fe2Al5 phase was fully transformed into the ductile FeAl phase after the hot-dipped samples annealed at 900 °C for 3 h. When the outermost layer of Q345 steel was the FeAl phase, oxidation resistance of the oxide was the best.

Dynamic growth model of Fe2Al5 during dissimilar joining of Al to steel using the variable polarity cold metal transfer (VP-CMT)

Further development of the car lightweight in automotive industry significantly depends on the reliability of the Al/steel dissimilar joint, since more and more Al alloy parts are used in the car manufacturing. It has been proved that the Al/steel dissimilar joint strength can be effectively increased when the intermetallic compound (IMC) growth, especially the Fe2Al5 layer thickness, is controlled at certain level. Because the Fe2Al5 is the dominant phase of the entire IMC layer in the Al/steel dissimilar joint, and cracks usually initiate at this location when damage is conducted. Therefore, for the automotive industry assembly line, the prediction model monitoring the Fe2Al5 layer thickness of each Al/steel weld seam is desired to ensure the dissimilar joint quality and reliability. In the present research, a numerical dynamic growth model based on element diffusion laws is established to calculate the IMC layer thickness of Fe2Al5 phase during the variable polarity cold metal transfer (VP-CMT) welding of aluminum to steel in the function of welding heat input and location. To build up effective connection between the welding heat input and the actual temperature history of Al/steel interface, a finite element analysis (FEA) model is customized for the present VP-CMT process. The Fe2Al5 layer thickness calculation results are further validated using electron back-scattered diffraction (EBSD) characterization under scanning electron microscopy (SEM), confirming a 2.3 % deviation between the model prediction and actual layer thickness.

Volume fraction effect of stainless steel on microstructure, interface, corrosion and wear behavior of stainless steel / aluminum bimetal composites

304 stainless steel (SS)/A356 aluminum bimetal composites were manufactured by vacuum-assisted melt infiltration casting successfully. SS chips with different volume fractions of 35%, 50%, 60%, and 65% were used in a composite structure. Low-cost, environmentally friendly production was achieved by using chips as reinforcing material. Dry sliding ball-on-disc tests were performed against Al2O3 ball under a load of 10 N. Potentiodynamic polarization analysis was carried out in 3.5% NaCl solution. θ (Fe4Al13) and η (Fe2Al5) phases developed at the SS/Al interfaces. Abrasive and adhesive wear predominated worn surfaces, whereas galvanic and pitting corrosion mechanisms originated during potentiodynamic polarization tests. Lower volume fractions of SS chips resulted in microploughing, while their higher amounts caused microcutting during sliding. Moreover, the samples containing 60% and 65% SS failed in the corrosion tests due to the lack of passivation. The most suitable SS ratio was determined to be 50%, considering microstructural, interfacial, tribological, and anti-corrosion features of SS/Al bimetal composites.

Improving the Quality of Dissimilar Al/Steel Butt-Lap Joint via Ultrasonic-Assisted Friction Stir Welding

A dissimilar AA7075/Q235 butt-lap joint was fabricated via ultrasonic-assisted friction stir welding (UaFSW), and the characteristics of the UaFSW joint were investigated systematically. The acoustoplastic effect of the ultrasonic vibration led to the softening of the materials and enhanced the material flow during welding, decreasing the volume of welding defects in the nugget zone of the UaFSW joint. With the help of ultrasonic vibration, a smooth and thin intermetallic compounds (IMCs) layer could generate along the Al/steel interface at the top of nugget zone, which possibly consisted of Al5Fe2 and Al13Fe4 phases. However, the positive effects of the ultrasonic vibration were weakened at low temperatures; consequently, the IMCs layer became discontinuous at the bottom of the nugget zone and the welding defects also formed. The ultrasonic vibration accelerated the dynamic recrystallization and refined the microstructures in the nugget zone due to the increased strain rate and stored energy. As a result, the UaFSW joint exhibited a better mechanical performance in comparison to the FSW joint, and the increment in the peak tensile load/elongation was more than twice. In addition, the UaFSW joint failed in the nugget zone along with the Al/steel interface, and the fracture mode was a mixture of ductile and brittle.

The preferential formation of Ni2Al3, Fe2Al5, and Ti2Al5 phases in aluminide systems

The preferential formation of phases in Ni–Al, Fe–Al, and Ti–Al systems was observed at the interface of solid-solid and solid-liquid phases. It was found that phases already formed at temperatures lower than the melting point of aluminum. The Ni2Al3, Fe2Al5 and Ti2Al5 phases formed preferentially in the Ni–Al, Fe–Al and Ti–Al systems, respectively. The favored formation was not associated with thermodynamic assumptions, but was caused by crystal structures of arisen phases. The mentioned phases could form due to the two reasons, (i) similarities of their lattice parameters to lattice parameters of the individual elements (Ni, Fe, Ti, or Al) and (ii) the total volume of its lattice. The lattice volumes of Ni2Al3, Fe2Al5, and Ti2Al5 phases are always smaller than that of NiAl3, FeAl3, and TiAl3 phases. The last listed phases are ordinarily accepted by other authors as the phases, which form preferentially based on thermodynamic data only. This work disproves such claims and shows the reason for preferential phases' formation.

The Effect of Multiple Thermal Process on Microstructural Evolution and Mechanical Properties of Additive Manufactured Al/Steel Structure

Wire and arc additive manufacturing (WAAM) provides a convenient solution for the integrated design and manufacturing of Al/steel structures. The multiple thermal cycles inherent in WAAM can affect the Al/steel interface and ultimately the overall performance of the Al/steel structure. Herein, the evolution behavior of the Al/steel interface microstructure under different WAAM modes, number of thermal cycles, and interpass temperature is investigated. The results show that the process of heat accumulation plays an important role in the evolution of Al/steel interface. As the number of thermal cycles increases, the intermetallic compounds layer gradually transforms from the mainly τ5‐Al8Fe2Si phase to (Al, Si)13(Fe, Cr)4 phase. The rise of interpass temperature significantly aggravates the microstructural evolution process, but the final interface structure can be manipulated employing temperature control. When the interpass temperature is lower than 250 °C, the formation of the brittle Fe2Al5 phase is avoided. With the increase of thermal cycles, the shear strength of Al/steel additive specimens increases first, then decreases, and finally tends to be stable. The changes in shear strength are closely related to the interface microstructures.

Microstructural Characterization and Mechanical Properties of Laser Beam-Welded Dissimilar Joints between A6000 Aluminum Alloy and Galvanized Steel.

This paper presents the laser beam welding process of a lap joint between galvanized steel (Z225) and an aluminum alloy (A6000) from an IPG fiber laser. Welding of steel to aluminum has become popular in the automotive industry as a means of reducing the total vehicle body mass. This approach reduces fuel consumption and, ultimately, carbon emissions. Laser welding parameters used to control heat input for the study were laser power ranging between 800 and 1200 W, as well as laser welding speeds between 2 and 4 m/min. Distinct features of the dissimilar joints were microscopically examined. The SEM-EDS technique was employed to study the intermetallic phases along the Fe-Al interface. The outcome revealed the presence of “needle-like phases” and “island-shaped phases” at high heat inputs. Traces of both Fe2Al5 and FeAl3 phases were detected. For low heat input, there was evidence of insufficient fusion. Weld width was influenced by welding parameters and increased with an increase in heat input. Mechanical properties of the joints indicated that the microhardness values of the weld joints were higher than those of both base metals. The maximum tensile shear strength obtained was 1.79 kN for a sample produced at 1200 W and 3 m/min.

Effect of austenitization on microstructure and corrosion resistance of Al-10Si-xZn-yMg coating

Through the heat treatment process of pre-alloying and then austenitizing, the effect of austenitizing on the microstructure and corrosion resistance of Al-10Si- x Zn- y Mg coating was investigated. After pre-alloying at 700 °C, the Al-Si alloy layer in the coating began to disappear. As the austenitizing temperature increased, FeAl and Fe 3 Al phases appeared in the coating. Moreover, as the austenitization time increased, the volume of the FeAl phase became bigger, and the volume of the Fe 2 Al 5 phase became smaller. The Si element and a small amount of Zn and Mg elements had always existed in the coating in the form of solid solution. The self-corrosion potential of Al-10Si and Al-10Si-10Zn-2Mg coatings after austenitization increased, while its self-corrosion current density first decreased and then increased, and was the smallest when the austenitizing temperature was 950 °C. Compared with Al-10Si coating, Al-10Si-10Zn-2Mg coating after austenitization at the same temperature had lower self-corrosion potential and self-corrosion current density. Therefore, the addition of Zn and Mg elements could improve the sacrificial protection and corrosion resistance of Al-10Si coatings. • Pre-alloying and then austenitizing were used in the heat treatment process. • Al-10Si- x Zn- y Mg coating after austenitizing was composed of Fe 2 Al 5 , FeAl and Fe 3 Al phases. • Zn and Mg elements dissolved in the Al-10Si-10Zn-2Mg coating after austenitizing. • Al-10Si-10Zn-2Mg coating can provide excellent cathodic protection for steel.

B2-ordered NiAl content on microstructure, mechanical and oxidation properties of FeAl intermetallic compounds

B2-ordered FeAl based materials with 0, 10, 20, 30, 40, 50 and 60 wt.% B2-ordered NiAl reinforced phase were prepared by mechanical alloying with subsequent hot-pressing sintering. The microstructure, mechanical properties and oxidation resistance were investigated. The results showed that after adding NiAl, the main phase was composed of B2-ordered NiAl, B2-ordered FeAl phase, a small amount of AlFe3C0.5 and α-Al2O3. With the increase of NiAl content, the hardness and compressive strength of NiAl/FeAl composites first increased and then decreased. When the content of NiAl increased to 30 wt.%, the hardness and compressive strength of NiAl/FeAl composite reached the maximum value of 50.30 HRC and 2053.43 MPa, which was 35.2% and 40.8% higher than FeAl alloy. Besides, with the increase of NiAl content, the formation of dense oxide film on the surface was easier and faster, and the oxidation resistance was gradually improved. When the content of NiAl increased to 60 wt.%, the oxidation weight gain of NiAl/FeAl composite was 0.19 mg/cm2. Compared with FeAl alloy, the oxidation resistance of 60 wt.% NiAl/FeAl was increased by 81%, and the thickness of oxide layer was reduced from 1.527 μm to 0.253 μm. At this time, the oxide on the surface of the oxidized sample was mainly composed of α-Al2O3, α-Fe2O3 and a small amount of NiO.