Fe-based Composites Research Articles

Inducing surface nanoporosity on Fe-based metallic glass matrix composites by selective dealloying

Nanoporosity (i.e. nanohole formation) is induced at the surface of Fe-based metallic glass matrix composites by selective chemical or electrochemical (at 1 V) etching of a Fe65Cu10Zr10B15 composite material using a 0.065 M HNO3 aqueous electrolyte. While electrochemical treatments are found to remove the Cu-rich precipitates present at the surface of this alloy, chemical etching (in absence of applied potential) only causes partial dissolution of the Fe-rich amorphous matrix. In both cases, the resulting pores exhibit random shapes and their lateral size ranges from a few tens to hundreds of nm. The investigated material is ferromagnetic at room temperature, both before and after dealloying and it does not crystallize during the (electro)chemical etching process. The contact angle in deionized water decreases in the dealloyed states in comparison with the as-spun ribbon. This procedure is appealing for applications that could benefit from the combination of increased surface area and the amorphous character (lack of crystallinity) at the surface of dealloyed metallic glass composite materials.

Effects of Molybdenum and Boron Additions of Fe-Based Metal Matrix Composites by Warm Compaction Method

Effects of Molybdenum and Boron Additions of Fe-Based Metal Matrix Composites by Warm Compaction Method

The coarsening behavior of γ′-Ni3(Ti, Al) phase in a precipitation strengthened Fe-based alloy

The γ′-Ni3(Ti, Al) phase is an important strengthening phase of Fe-based alloys and nickel-based superalloys, its coarsening behavior is very important for the strengthening effects. In this study, the precipitation behavior of γ′-Ni3(Ti, Al) phase in a thermally aged precipitation strengthened Fe-based alloy was evaluated during aging at 700 °C and 750 °C for different time using transmission electron microscopy (TEM) and atom probe tomography (APT). The results show that, the homogeneously distributed spherical γ′-Ni3(Ti, Al) particles with L12 structure which coherent with the matrix can be observed in all the aged samples. The size of the precipitate increases, while the number density of the precipitate decreases with aging temperature and time increasing. The volume fraction of γ′ particle is one key factor that influences the strength of bulk sample. During the process of γ′ particle growth, the partition ratios of Ni, Al and Ti between precipitates and matrix decrease with the aging temperature increasing significantly, while increase with aging time prolonging slightly. The Ti/Al ratio decrease with the aging time prolonging and aging temperature decreasing significantly. Based on the experiment results, the coarsening behavior of γ′ phase and their strengthening effects are discussed, which are expected to contribute to the design of Fe-based alloy compositions with improved mechanical properties.

Brittle-Ductile Transition in Laser 3D Printing of Fe-Based Bulk Metallic Glass Composites

The effects of the α-Fe phase on mechanical properties and cracking of laser 3D printing Fe-based bulk metallic glass composites were investigated. The elastic recovery and plasticity index were characterized by nanoindentation. As the volume fraction of the α-Fe phase increases from 23.66% to 52.38%, the elastic modulus of printed samples suddenly drops. The samples exhibit a lower deformation resistance, and the plasticity index increases gradually. When the volume fraction of the α-Fe phase is 67.84%, the interaction between the α-Fe phase and matrix phase is smaller during expansion shrinkage. As a result, cracking is easy to initiate, which leads to the highest crack rate of the printed sample. However, as the volume fraction of the α-Fe phase increases to 83.31%, the hard brittle phase was sandwiched between the α-Fe phases similar to the finger structure plays key role in the plastic deformation. The plastic deformation releases large amounts of stress concentrated at the boundary and suppresses crack formation.

High-temperature oxidation resistance of VCps-reinforced Fe-matrix composites using an in-situ reaction

The oxidation kinetics and behavior of vanadium carbide particle-reinforced Fe-based composites (VCps-Fe-MC) were investigated at 600, 800, and 950 °C. The microstructure of the surface and cross-section of the oxidation layer was characterized by scanning electron microscope (SEM). The composition of the surface of the oxide scales was examined by X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS). The micro hardness of the specimens was measured by a micro-hardness tester after a high-temperature treatment and subsequent air cooling. The results showed that the growth of the oxide scales on the VCps-Fe-MC followed a parabolic curve with an increase in the oxidation time. In addition, the weight gain increased with the oxidation temperature during the same period. Different oxide scales and oxidation rates occurred in some regions due to different textures. The minimum oxidation rate was in the austenite region because of a high silicon and chromium contents. At the same time, severe cracking and large shedding of the oxide scales were discovered due to growth stress and thermal stress. These defects can provide channels for oxygen diffusion. Based on the micro-hardness values, temperatures greater than 900 °C can be regarded as austenitizing temperatures during heat treatment to improve the mechanical properties and the wear resistance.

Influence of heat treatment on microstructures and magnetic properties of Fe-based soft magnetic composites prepared by co-precipitation method

Abstract Fe/(NiZn)Fe2O4 soft magnetic composites (SMCs) were prepared by the co-precipitation method using pure atomised iron powder and chloride as raw materials. The morphology and element content of coated powders were analysed using scanning electron microscopy and energy dispersive spectroscopy. Moreover, we used electron probe micro-analyser, X-ray diffraction and Raman spectrum to systematically investigate the effect of heat treatment temperature in argon on the microstructure of SMCs, including O element distribution, phase formation and internal stress. The results show that by increasing heated temperature, the oxygen content at the boundary of the SMCs increased and the internal stress release of SMCs was more complete. Moreover, non-magnetic FeO would be generated in SMCs when the heat treatment temperature reached 550 °C. We also discussed the relationship of heat treatment temperature and atmosphere with AC magnetic properties of the samples, including permeability, core loss and coercivity. The results indicate that the SMCs annealed at 450 °C in argon had the optimum magnetic performance (µ = 55.8, P cv = 12.2 kw/m3, H c = 22.6 A/m). At the heat treatment temperature of 500 °C, the argon-annealed samples presented better magnetic properties and higher frequency stability than air-annealed samples.

Effect of nickel reinforcement on electrochemical and wear behaviour of spark plasma sintered Fe-based metallic glass composites

Iron-based metallic glass composites reinforced with crystalline nickel ranging from 2.5 to 10 vol% were fabricated using spark plasma sintering. The effects of nickel reinforcement on microstructure, corrosion, and wear behavior of the metallic glass composites were investigated. While all composites exhibited lower corrosion resistance compared to monolithic metallic glass, the composites with lower reinforcement content (2.5 and 5 vol% Ni) showed some passivation effects in HCl solution. Also, as nickel is significantly softer than the metallic glass matrix, the hardness of sintered composites progressively decreased with increasing content of nickel. However, despite their lower hardness, the composites reinforced with lower nickel content (2.5 and 5 vol% vol%) exhibited improved wear resistance due to toughening effect. The wear resistance deteriorated with further increase in reinforcement content above 5 vol% Ni. The results show that Fe-based metallic glass composites with lower reinforcement content (2.5 to 5 vol% Ni) are promising in applications where optimum corrosion and wear performance is desired.

Understanding the effect of the reinforcement addition on corrosion behavior of Fe/Mg2Si composites for biodegradable implant applications

Abstract Iron-based materials showed a high potential for degradable biomaterial applications. However, their slow corrosion rate limits their use as a biodegradable implant material. One approach to control and modify their mechanical properties is the use of reinforcement particles, to create metal matrix composites in which the second phase is aimed at tuning not only the mechanical properties but also the corrosion mode and rate in a physiological environment. Here, Fe/Mg2Si composites were produced via powder metallurgy from pure Fe and Mg2Si powders. The different conditions were fabricated by various combinations of milling or mixing processes followed by hot rolling consolidation. The effect of the Mg2Si addition on corrosion behavior of Fe/Mg2Si composites was studied by performing cyclic polarization and static corrosion tests for an immersion time of 24 and 240 h. The presence of the reinforcement particles played a crucial role in the susceptibility of Fe-based composites to localized corrosion attack. The corrosion initiation and its development were systematically monitored. Scanning electron microscopy, X-ray diffraction, and atomic emission spectroscopy were employed to investigate the corrosion mechanism. The importance of Mg2Si particles in the triggering of corrosion processes was explained. Electrochemical measurements and static immersion tests implied that the introduction of Mg2Si particles could accelerate the corrosion rate of Fe. It was confirmed that the size and distribution of the reinforcement influenced considerably the uniformity of the corrosion attack.

In-situ formation of Fe3O4 and ZrO2 coated Fe-based soft magnetic composites by hydrothermal method

In this paper, the soft magnetic composite was prepared using a powder metallurgy method with the Fe3O4 and ZrO2 co-coated iron powder which was synthesized though the in-situ hydrothermal method. Energy dispersive spectroscopy (EDS) coupled with X-ray photoelectron spectroscopy (XPS) revealed that the Fe3O4 and ZrO2 were uniformly coated on the surface of iron powders. The addition of ZrO2 in the coating effectively improves the properties of the soft magnetic composite. ZrO2 can further improve the insulating properties, and enhance the thermostability of the coating simultaneously which will lead to resistivity increase and eddy current loss decrease. By controlling the additive amount of zirconium cation and annealing temperature, high magnetic induction of 1.002 T (measured at 8000 A/m), relatively high permeability of 83 (measured at 100 kHz), and low total core loss of 255.2 W/kg (measured at 100 kHz and 50 mT) were achieved. The Fe@ZrO2&Fe3O4 SMCs show high electrical resistivity and saturation induction, which may be widely used in high speed electric motor, transformer, inductance and switching power supply.

Hierarchical Nanosheet-Built CoNi2S4 Nanotubes Coupled with Carbon-Encapsulated Carbon Nanotubes@Fe2O3 Composites toward High-Performance Aqueous Hybrid Supercapacitor Devices.

A hybrid supercapacitor system was designed with ternary Ni-Co sulfides (CoNi2S4) as cathode materials and Fe-based composites [carbon nanotubes (CNTs)@Fe2O3@C] as anode materials to achieve excellent overall electrochemical performance with high energy and power density as well as long lifespan. Here, hierarchical CoNi2S4 nanotubes were synthesized by a solvothermal route followed by sulfidation reaction for the first time, in which nanotubes were composed of interconnected ultrathin nanosheets. Consequently, such a unique nanosheet-built nanoarchitecture enables the CoNi2S4 cathode with multidimensional synergistic effect from one-dimensional nanotubes, two-dimensional nanosheets, and three-dimensional frameworks. Profiting from its structural merits, the as-prepared CoNi2S4 nanotubes deliver a high capacitance of 2552 F g-1 at 1 A g-1 with a high rate capacity of 81% at 25 A g-1. In addition, the CNTs@Fe2O3@C anode materials-incorporating carbon-encapsulated ultrafine Fe2O3 nanoparticles into CNT matrices-were achieved by atomic layer deposition and acetylene thermal decomposition, which realize excellent electrochemical properties (678 F g-1 at 1 A g-1 and capacity retention of 82% at 25 A g-1) that matched well with CoNi2S4 cathode materials. With the well-designed nanostructure and matching of materials and properties, the corresponding aqueous hybrid device exhibits a wide output voltage window of 0-1.75 V with a maximum energy density of 90.5 W h kg-1 at a power density of 1.84 kW kg-1. Meanwhile, a high energy density of 73.1 W h kg-1 can be retained at an ultrahigh power density of 26.9 kW kg-1. Moreover, the hybrid device has a stable cycling ability with 82.1% retention over 5000 cycles. This coordinative design strategy integrating the cathode and anode electrodes developed in this work provides a novel way to manufacture next-generation energy-storage device with high performance and safety.

Dry sliding wear investigation on tungsten carbide particles reinforced iron matrix composites

WC particles reinforced Fe-based metal matrix composites were synthesized by powder metallurgy process. The microstructure and composition of the specimens were analyzed and the wear-resistant properties against WC and alumina balls were comparatively investigated by SEM/EDS analyses. The wear rates of specimens were evaluated by optical profilometry. Microstructure exhibited austenite Fe-FCC dendrites, eutectic (iron austenite + carbides) and primary carbides. Two wear mechanisms have been identified from SEM as main mechanisms during dry sliding wear of Tungsten carbides reinforced iron matrix, namely oxidation and abrasion. The overall wear performance, which is obtained by considering the wear loss of the substrates, indicated less resistance against Alumina compared to WC ball contact.

Extended Working Frequency of Ferrites by Synergistic Attenuation through a Controllable Carbothermal Route Based on Prussian Blue Shell.

One of the major hurdles of ferrite-based microwave absorbing materials is the limited working frequency that urgently calls for an effective modification technique. Herein, a controllable carbothermal route has been developed to ameliorate the microwave absorption performance of Fe3O4 nanospheres by using metal-organic frameworks (MOFs) shell as a carbon source with changing ramping rates. An enhanced synergistic attenuation induced by varied composition and tailored morphology is of great importance, which can be regarded as the superiority of the comprehensive (magnetic and dielectric), rather than unilateral (dielectric), modification technique. The drawbacks of dielectric modification can be concluded as the separated attenuation mechanisms at discrete frequencies, proven by the construction of the core-shell structured Fe3O4@Prussian blue composite. The advantages of magnetic modification can also be confirmed by a series of Fe-based composites with unique composition and tailored structure derived from the Fe3O4@Prussian blue composite at a distinct heating rate. Further, the superiority can be summarized as the rearrangement of magnetic loss by exceeding the Snoek limit and the reinforcement of dielectric loss by enhancing the electrical conductivity and introducing multiple polarization processes. Consequently, the sample obtained at 10 °C min-1, which contains Fe and Fe3O4, shows an extended working frequency of 14.05 GHz, with a thickness less than 5 mm and a high reflection loss value of -48.04 dB at 1.55 mm. This work not only offers a novel carbothermal route based on MOFs coating to prepare desired magnetic composites, but also acquires deeper insights of the comprehensive modification technique, which may pave the way for designing high-performance electromagnetic devices.

Laser additive manufactured WC reinforced Fe-based composites with gradient reinforcement/matrix interface and enhanced performance

Laser additive manufacturing has been proved to be a new technology for production of high-performance metal matrix composites with tailored interfacial structures. The WC particle reinforced Fe-based composites were manufactured by selective laser melting to investigate the effects of laser processing parameters on densification, microstructure and mechanical properties. The densification level increased with increasing laser power and decreasing scanning speed. The novel gradient interface formed around WC particles due to the in-situ reaction between WC particle and Fe-based matrix. After the optimization of laser processing conditions, the micro-hardness enhanced to 511.6 HV0.2 and a low friction coefficient of 0.30 was achieved with a low wear rate of 3.1 × 10−5 mm3/(Nm). The improvement in wear performance attributed to the synergistic effect of gradient interface, enhanced densification and novel microstructure.

3D printing of Fe-based bulk metallic glass composites with combined high strength and fracture toughness

Additive manufacturing is a promising technique for the production of bulk metallic glass (BMG) components without size limitations. However, the current additive manufacturing technique encounters the challenge of micro-cracking induced by huge thermal stress during the process, which significantly degrades the mechanical performance of the components. Based on systematic experiments combined with finite element simulation, we revealed that micro-cracks in inherently brittle Fe-based metallic glass during selective laser melting (SLM) are triggered by highly concentrated thermal stress around micro-pores, which is difficult to avoid during SLM even by careful process optimization. To suppress these micro-cracks, Cu and Cu-Ni alloys with high toughness as second phases were introduced to form BMG composites. The results revealed that the generation of high-density dislocations in second phases during SLM drastically reduce thermal stress by releasing strain energy and thus suppress micro-crack formation. Further investigation has shown that the introduction the second phase improves the fracture toughness of Fe-based BMGs to 47MPam1/2, which is approximately 20 times higher than that of the Fe-based BMG (2.2MPam1/2). Our findings provide general guidelines for the SLM fabrication of bulk metallic glass composites with tunable mechanical performances, as well as large sizes and freeform geometries.

Formation mechanism and phase evolution of in situ synthesizing TiC-reinforced 316L stainless steel matrix composites by laser melting deposition

Different weight ratios of 316L austenitic stainless steel, Cr3C2 and Ti powders were mixed to synthesize TiC-reinforced Fe-based composites by laser melting deposition. Fine TiC-particles were in situ synthesized through the reaction of Ti with Cr3C2 and were found to be uniformly dispersed in the matrix. The α-Fe phase was precipitated out of the γ-Fe matrix with the addition of Cr3C2 and Ti powders. The mechanism of TiC formation and phase evolution was analyzed based on thermodynamics calculations. The volume fraction and the size of the in situ synthesized TiC were found to affect grain texture of the γ-Fe matrix.

3D printing of Fe-based bulk metallic glasses and composites with large dimensions and enhanced toughness by thermal spraying

3D printing of Fe-based bulk metallic glasses and composites with large dimensions and enhanced toughness by thermal spraying

3D printing of Fe-based bulk metallic glasses and composites with large dimensions and enhanced toughness by thermal spraying

Large sized Fe-based bulk metallic glasses (BMGs) and BMG/stainless steel (SS) composites with excellent mechanical properties were successfully fabricated using a thermal spray three-dimensional (3D) printing (TS3DP) technique.

Well-defined Fe, Fe3C, and Fe2O3 heterostructures on carbon black: a synergistic catalyst for oxygen reduction reaction

Constructing Fe-based composites with a smart heterostructure, by using metallic Fe, Fe3C, Fe2O3 as building blocks, may open a door to rationally designing high-active and low-cost transition metal-based catalysts for the oxygen reduction reaction.

Comparison study of Fe-based matrix composites reinforced with Ti-coated and Mo-coated SiC particles

The comparison study of Ti-coated and Mo-coated SiC particles reinforced Fe-based matrix composites were investigated in this work. The Ti-coated and Mo-coated SiC particles were prepared by discharge treatment on a mixture of SiC particles and the corresponding metal powders in the SPS system. The coatings on Ti-coated SiC particles were composed of Ti, TiC, and Ti5Si3 phase, while Mo, Mo2C, MoSi2, Mo5Si3, and Mo3Si phase existed in the Mo-coated ones. The formed Ti coatings and Mo coatings on SiC particles were 300 nm and 500 nm in thickness, respectively. The Mo-coated SiC particles were better than the Ti-coated ones in improving the mechanical properties of SiC reinforced Fe-based matrix composites. It was estimated that the increased interface bonding strength between the Mo-coated SiC particles and the matrix was higher by 138 MPa than that between the Ti-coated SiC particles and the matrix.

Micro/nano ductile-phases reinforced Fe-based bulk metallic glass matrix composite with large plasticity

Fe-based bulk metallic glasses (BMGs) often show an extremely poor plastic deformation ability at room temperature, which seriously restricted their wide application. In this work, a series of in-situ (Fe77Mo5P9C7.5B1.5)100−xCux (x = 0, 0.1, 0.3, 0.5, 0.7, 1at%) BMG matrix composites were successfully developed by low purity industrial raw materials using copper mold casting. An (Fe77Mo5P9C7.5B1.5)99.9Cu0.1 BMG matrix composite reinforced by the dual heterogeneous structure with micro/nano α-Fe exhibits the highest ever reported compressive plasticity of ~ 6.6% during the testing rod with a diameter of 1.5mm. The origin of a large plasticity of this Fe-based BMG composite has been discussed according to the initiation of the shear bands and the instability of the shear banding.