FeAl Phase Research Articles

The effect of microwave radiation on the formation of quasi-crystalline phases in the Al- Cu- Fe system prepared by induction furnace

Aluminium- copper- iron quasi-crystals were prepared by melting raw materials and heat treatment process using microwave radiation at three temperatures of 600 °C, 700 °C, and 800 °C. Al- Fe alloy and Al- Cu alloy were prepared separately, then these two alloys were melted in an induction furnace. X-ray diffraction, scanning electron microscopy, and simultaneous thermal analysis were used to investigate the microstructural characteristics, fracture surface, and thermal behaviour. In these samples, the peaks related to the quasi-crystalline phase, θ, β- AlFe(Cu), λ- Al13Fe4, and ω-Al7Cu2Fe1 phase were detected. The intensity of the formed phases also changed with the temperature and duration of the heat treatment process. By performing the heat treatment process at 600 °C, the intensity of the peaks related to the quasi-crystalline phase has increased and the peaks related to the θ phase have completely disappeared. Also, by increasing the annealing temperature to 700 °C, the intensity of the peaks related to the quasi-crystalline phase increased compared to the sample annealed at 600 °C, but annealing at 800 °C reduced the intensity of quasi-crystalline phase peaks and λ- Al13Fe4 phase is completely dissolved, but some phases such as β- AlFe(Cu) and ω still remained, which implies these phases are stable even up to 1000 °C. The morphology of the quasi-crystalline was cauliflower with ridges on the fracture surface of the sample while uneven surfaces were in the form of quasi- cleavage. These results show that the quasi-crystalline phase can be developed in a much shorter time using microwave energy compared to common annealing methods.

Microstructure and Mechanical Properties of Stainless Steel/6082 Aluminum Alloy Heterogeneous Laser Welded Joint.

The microstructures and mechanical properties of laser penetration welded joints of overlap steel-on-aluminum were investigated. The structure of the intermetallic compound layer without interlayer consists of FeAl and FeAl3 phases. After the Ni-foil was added, the thickness of the intermetallic compound layer and the content of the brittle and hard Al-Fe phase decreased significantly, and some new phases of Al0.9Ni1.1 and FeNi were formed. It was found that the Ni interlayer enhanced the tensile property of the joint by about 40% and decreased the microhardness of the intermetallic compounds, which is attributed to the improvement of the toughness of the welded joint made by the Ni interlayer. It is an effective way to improve the mechanical properties of the laser welding joint by adding a nickel interlayer to improve the metallurgical reaction.

Precipitation hardening and structure evolution in hypereutectic Al-6 % Fe-Zr alloys subjected to ultrasonic melt processing

The objective of this research was to study the influence of Zr concentration and ultrasonic melt processing (USP) on the microstructure and precipitation hardening of a hypereutectic Al-6% Fe alloy. Such alloys have a good potential in high-temperature, wear-resistant, and conducting applications but suffer from coarse structure and low strength/ductility, which prevents their processing. The microstructure of the studied alloys consisted of primary Al13Fe4 intermetallics and (Al)+Al13Fe4 eutectic colonies, which were successfully refined by adding Zr and performing USP. The mechanisms of USP and Zr were confirmed for the Al-6 % Fe alloys with a range of Zr additions. The structure refinement led to improved hardness and tensile properties of the alloys. All studied alloys demonstrated strong precipitation hardening effect with hardness increasing 4–5 times, reaching 170 HV for the alloy with 0.4 % Zr after annealing at 400 ℃ for 20 hrs. The electrical conductivity increased from 25 % IACS in the as-cast alloy to 40% IACS in the annealed Al-6% Fe-0.4 % Zr alloy. The prime novelty of this work is a considerable increase of hardness upon annealing, i.e. more than 100 HV, in the Al-6 % Fe alloy with only minute traces of Zr (<0.01 %). The precipitation phenomena were investigated by transmission electron microscopy. The precipitation of the semi-coherent Al13Fe4 phase with Zr segregated to its surface was observed for the first time. All studied alloys (with minute and larger Zr additions) showed the precipitation of this phase, while the alloys with the larger amount of Zr also demonstrated the precipitation of the metastable L12 Al3Zr phase. Therefore, the properties improvement was attributed to the structure refinement and the formation of Zr-modified Al13Fe4 and Al3Zr precipitates in the microstructure.

A study of the Al-rich region of the Al–Fe–Ir alloy system

Phase equilibria in Al–Fe–Ir were studied at 850 and 1100 °C above 50 at% Al. The formation of the continuous ternary region of solid solutions was estimated along about 50 at% Al between the Al–Fe and Al–Ir β-phases. The binary M-Al13Fe4 and Al5Fe2 phases dissolve up to at least 10 and 5 at% Ir, the CIr-phase, Al3Ir, χIr-phase and Al9Ir2 up to ∼4, ∼9, ∼2.5 and at least 2.5 at% Fe, respectively. These binaries extend to the ternary compositions at approximately constant Al. Three ternary phases designated m, Ł and N were revealed. The m-Al13(Fe,Ir)4 phase of the Al13Os4-type structure (C2/m, a = 1.7406 nm, b = 0.41923 nm, c = 0.76459 nm, β = 115.78°) is formed at ∼Al75–76Fe6–9Ir18–15. A ternary hexagonal Ł-phase (a = 1.09034 nm, c = 0.77614 nm) is formed in a small compositional region around ∼ Al74Fe14Ir12. The structure of a complex ternary N-phase forming at ∼Al77.5Fe5.0–10.5Ir17.5–12 was not specified.

Phase Composition and Microstructure of Cast Al-6%Mg-2%Ca-2%Zn Alloy with Fe and Si Additions

Investigating the effect of Fe and Si is essential for any new Al-based composition, as these impurities can be easily found both after primary production and recycling. This study is dedicated to filling the gap in revealing the phase composition of an Al-6%Mg-2%Ca-2%Zn alloy after the combined and separate addition of Fe and Si. This was addressed by permanent mold casting and solid solution heat treatment. The investigation of slowly solidified samples also contributed to understanding potential phase transitions. It was found that the alloy containing 0.5%Fe can have nearly spherical intermetallics after heat treatment, whereas a higher Fe content brought the formation of a needle-shaped Al3Fe intermetallic. We explain this by the formation of a ternary α-Al + Al10CaFe2 + Al4Ca eutectic, which is more compact in as-cast condition compared to divorced binary α-Al + Al4Ca and α-Al + Al3Fe eutectics. Similarly, 0.5%Si readily incurred the formation of a needle-shaped Al2CaSi2 intermetallic, probably also by a binary reaction L → α-Al + Al2CaSi2. In the solidified samples, no Mg2Si phase was found, even in slowly solidified samples. This is contrary to the thermodynamic calculation, which suggests a peritectic reaction L + Al2CaSi2 Mg2Si. Interestingly, the addition of 0.5%Si caused an even coarser microstructure compared to the addition of 1%Fe, which caused the appearance of a primary Al3Fe phase. We conclude that the new alloy is more tolerable to Fe rather than Si. Specifically, the addition of 0.5%Fe can be added while maintaining a fine morphology of the eutectic network. It was suggested that the morphology of eutectic and solid solution hardening governed the mechanical properties. The strength of the alloys containing separate 0.5%Fe (UTS = 215 ± 8 MPa and YS 146 ± 4 = MPa) and the combined 0.5%Fe and 0.5%Si additions (UTS = 195 ± 14 MPa and YS ± 1 = 139 MPa) was not compromised compared to the alloy containing 0.5%Si (UTS 201 ± 24 = MPa and YS = 131 ± 1 MPa).

Effect of Si, Co, Fe contents and cooling condition on the microstructure of Al–Si–Co(–Fe) alloys

In this paper, several Al–Si–Co and Al–Si–Co–Fe alloys were prepared by varying the contents of Si, Co and Fe, solidified via fast and slow–cooling conditions. In the ternary Al–xSi–yCo (x = 6, 12, 18; y = 2, 4) alloys, the Co–rich phase is Al9Co2–type with a certain Si content, which can be marked as (Al,Si)9Co2. The Al9Co2–type phase exhibits developed dendrites and block–like morphologies under fast and slow cooling conditions, respectively. In the quaternary Al–xSi–4Co–yFe (x = 6, 12, 18; y = 2, 4) alloys, the formed intermetallic compound is Al13Fe4–type, containing a certain amount of Si and Co. It exhibits fine and coarse dendritic morphologies under fast and slow–cooling conditions, respectively. With the increase of Si content and Fe: Co ratio in the Al–xSi–4Co–yFe alloys, the Si content and Fe: Co ratio in the Al13Fe4–type phase increase synchronously. The hardness of Al–xSi–4Co–yFe alloys were tested, and it was found that the fast–cooling alloys have higher hardness than the slow–cooling ones, while the value of fast–cooling Al–12Si–4Co–4Fe alloy is the highest. Besides, comparing with Al9Co2, the Al13Fe4 phase has a much higher tendentiousness to precipitate from Al–Si–Co–Fe alloys. This work may be referred for the control of Co– and Fe–rich phases in Al–Si alloys, with the concept of altering element contents and solidification conditions.

In Situ SEM, TEM, EBSD Characterization of Nucleation and Early Growth of Pure Fe/Pure Al Intermetallic Compounds.

The nucleation and growth processes of pure Fe/pure Al intermetallic compounds (IMCs) during heat treatment at 380 °C and 520 °C were observed through in situ scanning electron microscopy (SEM). The size of the IMCs were statistically analyzed using image analysis software. The types and distribution of IMCs were characterized using transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). The results showed that: at 380 °C, the primary phase of the Fe/Al composite intermetallic compounds was Fe4Al13, formed on the Fe side and habituated with Fe. The IMC was completely transformed from the initial Fe4Al13 to the most stable Fe2Al5, and the Fe2Al5 was the habitus with Fe during the process of holding at 380 °C for 15 min to 60 min. At 380 °C, the initial growth rate of the IMC was controlled by reaction, and the growth rate of the thickness and horizontal dimensions was basically the same as 0.02-0.17 μm/min. When the IMC layer thickness reached 4.5 μm, the growth rate of the thickness changed from reaction control to diffusion control and decreased to 0.007 μm/min. After heat treatment at 520 °C (≤20 min), the growth of IMC was still controlled by the reaction, the horizontal growth rate was 0.53 μm/min, the thickness growth rate was 0.23 μm/min, and the main phase of the IMC was the Fe2Al5 phase at 520 °C/20 min.

Microstructure and mechanical properties of induction rolling welded joint for A283GRC steel and 5052 aluminum alloy

In order to realize the welding of Fe/Al composite structure of automobile body, an induction rolling welding (IRW) was proposed. In this method, the eddy current and rolling force were generated by an induction heater and a rolling device respectvely, which were applied on the steel surface together. The Fe/Al welded joint under the combined action of eddy current heat and rolling force can be formed. The input power, feed velocity and rolling force were considered in this process. The results showed that IRW can realize the welding of A283GRC steel and 5052 aluminum alloy successfully. A continuous, uniform macroscopic morphology of welded joint and an optimal shear strength with 75 MPa can be obtained with the power 35 kW, the feed velocity 1 mm/s, and the rolling force 800 N. The intermetallic compound (IMC) in the welded joint consists of a lingulate Fe2Al5 towards the steel matrix and a saw-tooth FeAl3 towards the aluminum alloy matrix. The Fe2Al5 phase has the smallest Gibbs free energy and is the first to be generated at the interface. The weld joint width and IMC thickness in the IRW process increase with increasing power and decreasing feed velocity due to a larger heat input and longer heating time while increases with increasing rolling force due to a higher heat conducting efficiency. The shear strength can be increased significantly with increasing rolling force, due to a more contact area on the interface and a finer grain near the interface, which can prevent cracking effectively.

Interfacial microstructure, element diffusion, mechanical properties and metallurgical bonding mechanism of 316L-AlSi10Mg multi-material parts fabricated by laser powder bed fusion

This work explored the interfacial microstructure, element diffusion, mechanical properties and metallurgical bonding mechanism of 316L-AlSi10Mg multi-material parts fabricated by laser powder bed fusion (LPBF). Experimental results revealed that insufficient volumetric energy density (VED) of the laser caused lack-fusion porosity in the 316L-AlSi10Mg transition zone, while too high VED produced keyhole-induced porosity defects. Using the optimal process parameters, multi-material parts can be produced with a good interface metallurgical bonding without significant defects. The partial Fe-FCC phase in 316L stainless steel changed into the Fe-BCC structure, and this shift has also changed the preferred orientation of the grains. The intermetallic compound Al5Fe2 and AlFe phases were found in the transition zone. In addition, Al–Fe icosahedral quasicrystals with five-fold symmetry were found at the boundary of the molten pool, which was caused by an extremely high cooling rate. The tensile strength of 316L-AlSi10Mg specimens is higher than that of AlSi10Mg but lower than that of 316L. In contrast to the 316L and AlSi10Mg regions, the fracture mechanism of multi-material fusion zone exhibits a quasi-cleavage fracture mode. The Vickers microhardness of the Al–Fe interface zone was higher than that of 316L with an average value of 235.57 HV0.2 and AlSi10Mg with 124.59 HV0.2, and the interfacial maximum hardness reached 526.68 HV0.2, which was caused by the very hard intermetallic compound Al5Fe2 and AlFe. The metallurgical bonding mechanism of multi-materials was that the dissimilar metals were mixed and in-situ alloyed in the molten pool by the Marangoni convection-induced strong circular flow during LPBF processing.

The effect of aluminide coating on the steam oxidation behavior of SS321 steel at 700 °C

Steam oxidation is considered the main attack form involved in the destruction of superheater tubes in the superheater of water-tube boiler. In this work, the effect of an aluminide coating on the way steam reacts with SS321 steel in a superheater was studied. Aluminide coating was done by powder cementation at 800 °C for 7 h and then heat treatment at 900 °C for 1 h. The coating was made with an Al-rich Fe2Al5 phase, with an inner (diffusion) layer of 5 μm and an outer layer of 25 μm. The grains were all the same size, and there were few holes. The samples were subjected to a constant stream of supersaturated water vapor at a temperature of 700 °C. The weight gain of uncoated and coated samples was measured as 1 mg cm−2 and 0.5 mg cm−2 after 20 h, and 2.5 mg cm−2 and 0.7 mg cm−2 after 350 h, respectively. The remarkable weight loss of the coated samples after 20 h and up to 350 h was attributed to the formation of stable Al2O3 oxides. This was although in the uncoated samples, the outer and inner layers of the coating were composed of Fe-rich oxides (magnetite) and Cr-rich oxides (Cr-Fe spinel oxides), respectively. Microstructural studies showed that with the increase in oxidation time, the inner layer (diffusion) increases from 5 μm to 25 μm, which is attributed to the diffusion of substrate particles towards the coating during oxidation.

Elucidation on the correlation between thermal stability of Al13Fe4 intermetallic phase and mechanical properties of the Al-Fe alloy fabricated via friction stir alloying

Al-Fe alloy containing nanosized Al13Fe4 phase was fabricated by the solid-state multiple pass friction stir alloying (FSA) technique and subjected to heat treatment at different time-temperature conditions. During annealing, the diffusion of Fe atoms leads to the necking and fragmentation of the coarse plate shape Al13Fe4 IMC phase resulting in its spheroidization. However, as the annealing time is extended, the spheroidized Al13Fe4 phase undergoes coarsening and grows predominantly along a specific plane. This growth process transforms the originally spherical shape into an elliptical or small plate-like morphology. The grain size was insignificantly affected by the annealing time and temperature owing to the grain boundary pinning by the nanometric-sized IMC phase. The ultimate tensile strength of the Al-Fe alloy (149 MPa) is improved significantly at the annealing conditions of 200 °C/4hrs (165 MPa), 200 °C/6hrs (167 MPa), and 300 °C/2hrs (163 MPa). The improved UTS is attributed to the increased isotropic work hardening owing to the reduced IMC particle size and mean interparticle spacing in the Al-Fe alloy. The lowest work hardening rate is observed in the specimen annealed at 200 °C for 2 hrs (largest particle size) which is attributed to the stored energy in the material due to severe plastic deformation (SPD) associated with the FSA. The correlation between the work hardening rate, IMC particle size, and mean interparticle spacing at various annealing conditions are established.

Evolution mechanism of intermetallic compounds and the mechanical properties of dissimilar friction stir welded QP980 steel and 6061 aluminum alloy

Intermetallic compounds (IMCs) play an important role in the welding quality of steel and aluminum (Al) alloys by friction stir welding (FSW). However, the evolution mechanism of IMCs and their effects on the mechanical properties of FSW joints are still unclear and need to be further elucidated. In this work, QP980 steel and 6061 Al alloy are successfully welded by FSW. The microstructure and mechanical properties of joints are characterized. The results show that an IMC layer composed of Al3Fe, Al5Fe2, Al2Fe, and Al6Mn phases is generated at the weld interface. The joint efficiency is about 70.1%. The formation sequence of IMCs in the same binary system is affected by the effective enthalpy of formation, while it is related to the element concentration in different binary systems. Furthermore, the formation sequence is Al3Fe, Al5Fe2, Al2Fe, and Al6Mn phases. The interfacial bonding strength is enhanced by the low lattice mismatch between IMCs and matrix. The interfacial bonding strength of IMCs with Fe and Al matrices in the joint is in ascending order: Al2Fe and Fe, Al2Fe and Al, Al5Fe2 and Fe, Al5Fe2 and Al, Al6Mn and Fe, Al3Fe and Fe, Al6Mn and Al, as well as Al3Fe and Al. It is noted that the bonding strength between the Al2Fe and Fe is lowest, indicating that Al2Fe phase is responsible for the joint fracture during tensile test.

Synthesis and Microstructure Characterization of Fe-Cr-Al Alloys Developed by Powder Metallurgy Technique with Plasma Sintering Method

Synthesis of Fe-Cr-Al alloy by powder metallurgy method was developed to produce a bioimplant material with a low modulus of elasticity. Microstructure characterization and phase identification were carried out to support the development of bone implant material research. The alloys were synthesized with the elemental composition of 16 Cr (wt%) that was added with Al in variations of 3, 6, and 10 (wt%). The synthesis was carried out by an exceptional combination of mixing and mechanical milling, cold compacting and consolidating with a special method using the APS (Arc Plasma Sintering) apparatus. Microstructure characterization and phase identification were analyzed by SEM-EDS and XRD tests. The microstructure showed relatively homogeneous fine grain with small porosity of around 80 %. Refinement of the XRD peak pattern revealed the formation of the Fe-Cr main phase followed by the Fe-Al phase with Al as the solid solution. The hardness test showed a high hardness level with a maximum for Fe-16Cr-6Al (wt%) of around 160 VHN (Vickers Hardness Number). The quantity of Fe-Cr phase and the composition of Al influenced the hardness of the alloy.

Comparative study of Pr/PrFe/PrAl grain boundary diffusion processed Nd–Ce–Fe–B sintered magnets with high Ce substitution: Evolutionary microstructure and magnetic responses

Owing to high natural abundance, surplus stockpile and low price of Ce, the Nd–Ce–Fe–B magnet possesses outstanding advantages as a novel permanent alternative with reduced critical rare earth (RE). However, the wide application of Nd–Ce–Fe–B magnet with high Ce substitution is still impeded by the low-coercivity issue. Here we report a comparative study of Pr/PrFe/PrAl grain boundary diffusion processed (GBDP) Nd–Ce–Fe–B sintered magnets to unravel the evolutionary microstructure and magnetic responses towards higher coercivity. Via Pr diffusion-induced microstructural engineering, continuous REFe2 and RE-rich/Fe-lean intergranular phases coexist at a long diffusion depth, with concurrent formation of thick Pr-rich shell surrounding RE2Fe14B grains. The resultant magnetic performance with Hcj = 14.4 kOe, Br = 13.2 kG, and (BH)max = 41.0 MGOe reaches the highest level reported so far upon high Ce substitution of 40 wt%, revealing that Pr GBDP successfully manages to overcome the coercivity-remanence trade-off. For PrFe GBDP, significant quantities of Fe are redistributed to inevitably form Ce-rich REFe2 precipitates at the outmost diffusion surface, which retard the diffusion efficiency and limit the depth of continuous Pr-rich GBs/shells compared to pure Pr diffusion. For PrAl GBDP, extra Al induces ferromagnetic RE–Fe–Al phase to replace REFe2 phase at a deeper diffusion depth, which limits the coercivity increment. Further micromagnetic simulations coincide with the experimental results, revealing the priority of regulating non-ferromagnetic GB phase towards high-coercivity Nd–Ce–Fe–B. Above findings not only deepen our understanding on distinct metallurgical behaviors of Pr/PrFe/PrAl diffusion, but also delight future work on developing Ce-rich Nd–Ce–Fe–B magnets.

Improvement of Microstructure and Sliding Wear Property of Cold-Sprayed FeAl Intermetallic Compound Coating by Annealing Treatment

Nanograin Fe(Al) solid solution alloy coating was firstly produced through cold-spraying technology using mechanically alloyed powder. Then, the above-mentioned coating was annealed at different temperatures to explore its influence on the phase constitution, microstructure, microhardness and dry sliding wear property of the coatings. Results exhibited that an FeAl phase appeared in the coatings after 500 °C treatment and remained stable with increasing annealing temperature. The annealing temperature had a considerable effect on the microstructure, microhardness and wear behavior of the FeAl coating. The existing laminated structure in the as-sprayed coating gradually faded away with increasing temperature and finally obtained a dense coating microstructure with no particle interface when annealed above 950 °C. Nanograin began to evidently grow at temperatures over 800 °C. The microhardness of the FeAl coating stayed at 400 Hv0.1 at temperatures below 800 °C, then it quickly dropped to 300 Hv0.1 at 950 °C and remained nearly unchangeable up to 1100 °C. The dry sliding wear mechanism of the FeAl coating annealed at low temperatures below 700 °C was mainly delamination of the oxide layer and showed a high wear rate within the order of magnitude range of 10−4, whereas FeAl coatings annealed at high temperatures above 950 °C were worn by microploughing and little oxidation and exhibited very low wear rates within the order of magnitude range of 10−6.

Influence of annealing on the structure and wear resistance of coatings produced by cold spraying of Al–SHS7574 powder mixture

In present work, the possibility of fabricating a composite cold-sprayed coatings consisting of partially amorphous alloy reinforcing particles and an aluminum matrix was studied for the first time. A mixture of pure aluminum and SHS7574 powders in a ratio of 50/50 wt% was deposited on aluminum alloy substrates, which ensured the formation of high-quality coating with a porosity of less than 1%. The ratio of SHS7574 alloy to aluminum in the as-sprayed samples was nearly the same as in the initial powder mixture which indicates a similar efficiency of component deposition. Composite coatings were annealed in a vacuum furnace at 540 °C and 600 °C. Microstructure and phase composition of as-sprayed and annealed coatings were examined with XRD, SEM and EDX mapping. Post annealing of the coatings promoted the formation of a reaction layers around the Fe-based alloy particles consisting of Fe2Al5, Fe4Al13, Fe23B5, and Fe5C2 phases. The effect of annealing on the mechanical properties of the Al–SHS7574 coatings was determined by measuring hardness, nanohardness and wear resistance according to ASTM G 133–05. The increase in the samples’ hardness after annealing was associated with the formation of a reaction layers and increase in its thickness with rising annealing temperature. The coating annealed at 600 °C demonstrated the highest hardness due to the formation of thick brittle reaction layers. The preservation of the aluminum matrix with the simultaneous formation of thin reaction layers after annealing at 540 °C reduced the wear rate of the coating despite the moderate hardness.

R4 Kalite Açık Deniz Demirleme Zinciri Çeliğine Uygulanan Bor-Alüminid Kaplamanın Çukurlaşma ve Tribo-Korozyon Davranışına Etkisi

Offshore mooring systems are susceptible to wear, corrosion, and fatigue damage, making improving their tribocorrosion resistance essential. This study aims to evaluate the effects of boron-aluminizing treatment on the corrosion and tribocorrosion resistance of R4 steel in a marine environment. The boron-aluminide coating was characterized by SEM, EDS, and XRD, revealing the presence of FeAl as the dominant phase with minor amounts of FeB, Fe2B, and Fe2Al5 phases. Results showed that the boron-aluminide coating improved the corrosion resistance of R4 steel, acting as a barrier between the coating and the steel substrate and maintaining its corrosion resistance even under wear conditions. The findings suggest that the boron-aluminide coating can potentially improve the corrosion and tribocorrosion resistance of R4 steel in marine environments, making it a cost-effective alternative to passive materials for the thermochemical coating of low-alloy steels.

Effect of high entropy alloy as the interlayer on the interfacial microstructure and mechanical property of Al/steel bimetal by compound casting

Al/steel bimetal prepared by compound casting process exhibits an increasing application prospect in the lightweight field due to the combination of the advantages of Al alloy with steel materials. Unfortunately, a large number of hard and brittle Al–Fe intermetallic compounds (IMCs) are prone to form at the interface, resulting in insufficient interfacial bonding strength of Al/steel bimetal. Therefore, in the present work, the typical CoCrFeNiMn high entropy alloy (HEA) coating fabricated by laser cladding technique was used as the interlayer of Al/steel bimetal to suppress the Al–Fe IMCs. The results showed that the reaction layer of Al/steel bimetal with HEA interlayer first forms Al5Co2 rather than Al5Fe2 phases compared with the as-cast bimetal. More importantly, the Al5Co2 phase layer consists of nanocrystals. Besides, the elements like Cr, Ni and Mn are uniformly distributed into the reaction layer and no IMCs are detected. This contributes to a reduction in the grain size of Al5Fe2 phase. Although the characteristic of brittle with respect to Al5Co2 compound, the interfacial bonding strength of bimestal is improved by 33% compared with that of the as-cast bimetal, attributing to the fact that the nanocrystals formed at the interface make the surface energy and defect size increase in terms of Griffith's theory. In short, laser cladded CoCrFeNiMn HEA coating provides a new choice for the interlayer selection of Al/steel bimetal.

Microstructure and properties of in situ synthesized Fe-Al coating by laser cladding

To improve the hardness and wear resistance of an aluminum alloy, Fe-Al intermetallic coatings are synthesized in situ on the surface of aluminum alloys by laser cladding. An x-ray diffractometer (XRD) and a scanning electron microscope are used to characterize the phase and microstructure of the coating. The corrosion resistance, wear resistance, and hardness of the coating were measured by an electrochemical workstation, a reciprocating friction and wear tester, and a Vickers hardness tester, respectively. There are no pores but some microcracks in the coating. The coating structure is composed of a dendrite crystal, a columnar crystal, and an equiaxed crystal. The XRD results show that the Fe-Al coating is mainly composed of body-centered cubic solid solution, FeAl phase, and Fe3Al phase. At the same time, the average hardness of the coating reaches 601.54 Hv0.2, which is approximately 5.9 times that of the substrate (101.8 Hv0.2). Compared with the substrate, the self-corrosion voltage of the coating in 3.5% NaCl solution increased by 0.41 V, the self-corrosion current reaches 1.65 × 10−5 A, and the protection rate increased by 71%.

The effect of milling time on the preparation of an aluminum matrix composite reinforced with magnetic nanoparticles

Powder metallurgy methods, particularly ball milling, are up-and-coming in tuning metal matrix composite (MMC) properties. This study uses ball milling at various milling times to create an aluminum matrix composite (AMC) reinforced with magnetite nanoparticles. The milling time was optimized to create an AMC with favorable mechanical and magnetic properties, and its effect on magnetism, microstructure, and hardness was studied.The AMC displayed the highest magnetic saturation of 11.04 emu/g after 8 h of milling. After compaction and sintering, characterization of the final composite material using Energy Disperse Spectroscopy and X-ray diffraction (XRD) showed the presence of Al2O3 and Fe3Al phases leading to enhanced mechanical properties in terms of Vickers hardness that reached a value of 81 Hv corresponding to an increase of 270% compared to unreinforced aluminum.