Fe-based Alloys Research Articles

Investigation of glass forming ability, crystallization behavior, and soft magnetic properties of Fe–B–P–C–Cu alloy ribbons

The effect of Cu content on GFA, crystallization behavior, and soft magnetic properties in high P Fe84+xB6P6C3Cu1−x (x = 0, 0.2, 0.4, 0.6, and 1.0 at. %) alloy ribbons were systematically investigated to balance the relationship between glass forming ability (GFA), heat treatment window, and soft magnetic properties of high saturation magnetic flux density (Bs) Fe-based nanocrystalline alloys. It was discovered that lowering Cu promotes the formation of an amorphous structure. The GFA of alloys rises from 23 μm for Fe84B6P6C3Cu1 to 29 μm for Fe84.4B6P6C3Cu0.6. Analysis of thermal physical properties shows that when Cu content is between 1.0 at. % and 0.6 at. %, reducing Cu in the alloys does not affect the onset temperature of the first crystallization peak (Tx1), the second one (Tx2), and ΔT (ΔT = Tx2 − Tx1), whereas when Cu content is less than 0.6 at. %, reducing Cu leads to an increase in Tx1 and a decrease in Tx2 and ΔT, which is not conducive to obtaining a wide temperature range of precipitation of a single α-Fe phase. The alloys have a wide range of crystallization annealing temperature (693–753 K) and annealing time (60–6 min) to obtain a low coercivity (Hc) of about 8.0 A/m, high Bs of about 1.80 T, and high effective magnetic permeability (μe) of about 10000 when Cu is between 1.0 at. % and 0.6 at. %. The Bs, Hc, and μe of Fe84.4B6P6C3Cu0.6 alloy annealed at 723 K for 30 min are 1.82 T, 8.1 A/m, and 10820, respectively.

Evolution and Removal of Inclusions in Fe-Based Amorphous Alloys

Evolution and Removal of Inclusions in Fe-Based Amorphous Alloys

Improvements in Hot Corrosion Behavior of CO2 Laser-Welded Fe-Based A-286 Alloy in an Aggressive Salt Environment by High-Velocity Oxy-Fuel Coating

Improvements in Hot Corrosion Behavior of CO2 Laser-Welded Fe-Based A-286 Alloy in an Aggressive Salt Environment by High-Velocity Oxy-Fuel Coating

Development of Fe-based amorphous alloy with high iron content for room-temperature magnetic refrigeration application

In this work, in order to develop new Fe-based amorphous alloys with room-temperature magnetocaloric effect and good magnetocaloric performance, high iron content Fe-based amorphous alloys were designed, and their Curie temperatures were adjusted to room temperature through the addition of Mo. As a result, a new Fe83Mo6Si1B7P2C1 amorphous alloy with room-temperature magnetocaloric effect was successfully prepared by melt-spinning technique, and it has the Curie temperature of 300 K, the maximum isothermal magnetic entropy change of 2.74 J kg−1 K−1 and the refrigerant capacity of 485.2 J kg−1 under an applied magnetic field of 5 T. Combining with the advantages of excellent magnetocaloric properties, negligible hysteresis loss, and low material cost, the present Fe83Mo6Si1B7P2C1 amorphous alloy should be a promising candidate as room-temperature magnetic refrigerants.

The dynamic load-bearing performance of the laser cladding Fe-based alloy on the U75V rail

The microstructures of the Fe-based alloy laser cladding layer were characterized by optical microscope, scanning electron microscope and X-ray diffractometer. The load-bearing performance was evaluated and compared with that of the U75V rail. 3D finite element modelling was performed using the ANSYS software. It is found that the phases of the coating are α-Fe, Fe-Cr, Ni-Cr-Fe and Fe2B, Fe3Si precipitates. The average microhardness of the coating can reach HV455.2, which is higher than that of the heat affected zone (HAZ) and the substrate. The coating can effectively reduce the wear and rolling contact fatigue of heavy-haul rail.

Insights into the assessment of the magnetic-field-induced precipitation behavior of alloy carbides M7C3 in steels

A combination of first-principles calculations, Weiss molecular field theory and density functional perturbation theory is combined to systematically evaluate the magnetic-field-induced thermodynamic properties of the alloy carbide M7C3 in steel. Special emphasis is focused on the self-magnetic and the external magnetic-field-induced magnetic contribution determined by extending the magnetic heat capacity. The self-magnetism origins from the 3d orbit contribution of the Fe atoms which constituted the carbon-containing trigonal prism. The magnetic-field-induced Curie temperature which triggers the boundary of the long and short-range magnetic order closely related to the Cr content and the magnetic field strengths. The higher external magnetic-field-induced Gibbs energy change provides a potential precipitation strategy in advance for the alloy carbides M7C3 which is well in agreement with the experimental results. Our insights further will extend the mechanistic understanding of magnetic-field-induced phase transformation in ferromagnetic Fe-based alloys, emphasizing the role of external field in minimizing energy and guiding new alloy design.

The Effect of Alloy Composition on The Dealloying of Ni- and Fe-Based Engineering Alloys in Boiling Caustic Solutions

The effect of alloy composition on the dealloying susceptibility of Ni- and Fe-based alloys is studied in near-boiling caustic solutions. A comprehensive comparison of the alloys is performed using electrochemical measurements and nanoscale characterization to evaluate dealloying behaviour. Results indicate a general increase in dealloying resistance when Ni content is increased. In alloys with similar Ni content, higher Cr content delays dealloying, while an increase in Mo content promotes dealloying. Nanoscale characterization confirms a nanoporous surface film with a core–shell ligament structure. The shell is nearly pure Ni, while ligament cores have a composition approaching that of the parent material.

Effects of interfacial interactions between metal and process control agents during ball milling on the microstructure of the milled Fe-based nanocrystalline alloy powder

Fe–Si–B–P–Cu nanocrystalline alloy were treated with ball-mill using a lubricant as a process control agent (PCA). The resulting alloy powder is a strong candidate material for soft magnetic composites. Two ball milling methods (continuous and interval) were employed to control the interactions between the PCA and the alloy surface, and their effect on the microstructure of the prepared alloy particles was investigated. The alloy sheet was broken into small pieces and deformed plastically into flake-shaped particles regardless of the ball milling method implemented. Friction-force microscopy of the alloy immersed in the PCA revealed that the friction coefficient of the alloy surface exposed to air for a certain period was higher than that of the unexposed alloy surface (immediately after polishing). During ball milling, the ratio of the newly generated surface to the oxidized surfaces of the alloy subjected to interval milling was smaller than that of the alloy subjected to continuous milling. Therefore, the friction coefficient of the surface of the alloy subjected to interval milling was higher than that of the alloy subjected to continuous milling. Synchrotron radiation analysis revealed that the alloy subjected to interval milling exhibited enhanced surface friction, showing an obvious steepness and inflection in the diffraction intensity as a function of the tilt angle based on the Schulz reflection method. This indicates formation of crystallographic texture in α-Fe grains in an amorphous matrix. Hence, we demonstrated successfully that the ball milling process induced a crystallographic texture in the Fe-based nanocrystalline alloy due to plastic deformation due to the enhanced surface friction. The surface of the alloy was prepared based on the effect of the interfacial interactions between the alloy surface and the PCA.

Recent Advances and Remaining Challenges in Manufacturing of Amorphous and Nanocrystalline Alloys

A review of advanced Fe-based amorphous and nanocrystalline soft magnetic alloys that are currently being used in the market and their primary industrial applications is discussed as well as emerging trends. The high-efficiency distribution transformer market continues to be the largest segment by volume for Fe-based amorphous foil. The industry has been shifting toward higher induction levels (1.63 T) with increased stacking factor (>90%) to minimize the transformer size and reduce costs. New magnetic domain refined grades of amorphous foil are now commercially available which show a reduction of ~25% in core losses compared to the standard amorphous material. Nanocrystalline soft magnetic alloys have become the standard material for many applications including low-loss electrical components, magnetic shielding, electronic filtering, medium frequency transformer cores, and a variety of others. The nanocrystalline alloys are commonly cast fully amorphous and devitrified through controlled heat treatments. New nanocrystalline alloy compositions and processing methods have enhanced both the mechanical and magnetic performance of the final properties. Amorphous and nanocrystalline alloys show promise for use in electric motors but fabrication challenges for limited their commercial adoption.

The Effect of Mn on the Mechanical Properties and In Vitro Behavior of Biodegradable Zn-2%Fe Alloy

The attractiveness of Zn-based alloys as structural materials for biodegradable implants mainly relates to their excellent biocompatibility, critical physiological roles in the human body and excellent antibacterial properties. Furthermore, in in vivo conditions, they do not tend to produce hydrogen gas (as occurs in the case of Mg-based alloys) or voluminous oxide (as occurs in Fe-based alloys). However, the main disadvantages of Zn-based alloys are their reduced mechanical properties and their tendency to provoke undesirable fibrous encapsulation due to their relatively high standard reduction potential. The issue of fibrous encapsulation was previously addressed by the authors via the development of the Zn-2%Fe alloy that was selected as the base alloy for this study. This development assumed that the addition of Fe to pure Zn can create a microgalvanic effect between the Delta phase (Zn11Fe) and the Zn-matrix that significantly increases the biodegradation rate of the alloy. The aim of the present study is to examine the effect of up to 0.8% Mn on the mechanical properties of biodegradable Zn-2%Fe alloy and to evaluate the corrosion behavior and cytotoxicity performance in in vitro conditions. The selection of Mn as an alloying element is related to its vital role in the synthesis of proteins and the activation of enzyme systems, as well as the fact that Mn is not considered to be a toxic element. Microstructure characterization was carried out by optical microscopy and scanning electron microscopy (SEM), while phase analysis was obtained by X-ray diffraction (XRD). Mechanical properties were examined in terms of hardness and tensile strength, while corrosion performance and electrochemical behavior were assessed by immersion tests, open circuit potential examination, potentiodynamic polarization analysis and impedance spectroscopy. All the in vitro corrosion testing was performed in a simulated physiological environment in the form of a phosphate-buffered saline (PBS) solution. The cytotoxicity performance was evaluated by indirect cell viability analysis, carried out according to the ISO 10993-5/12 standard using Mus musculus 4T1 cells. The obtained results clearly demonstrate the strengthening effect of the biodegradable Zn-2%Fe alloy due to Mn addition. The effect of Mn on in vitro corrosion degradation was insignificant, while in parallel Mn had a favorable effect on indirect cell viability.

Molten chloride salt technology for next-generation CSP plants: Compatibility of Fe-based alloys with purified molten MgCl2-KCl-NaCl salt at 700 °C

Molten chlorides, such as MgCl2-KCl-NaCl, are promising advanced high-temperature (up to 800 °C) thermal energy storage (TES) materials in next-generation concentrating solar power (CSP) plants. However, their high corrosivity to commercial Fe-Cr-Ni alloys impedes the commercial applications of chloride-TES. In this work, we investigated the corrosion of two selected commercial Fe-based alloys (SS 310 and In 800H) in molten MgCl2-KCl-NaCl salt, aiming to study the feasibility of affordable Fe-based alloys instead of expensive Ni-based alloys in the chloride-TES system. The alloy samples were immersed in the liquid-Mg-purified molten salt at 700 °C for 2000 h under a protective inert gas atmosphere. After the corrosion test, SEM-EDX microstructural analysis and mass loss analysis showed that corrosion rates of the immersed alloy samples were lower than 15 µm/year, and the corrosion rates had a decreasing tendency with increasing immersion time during the 2000-hour test. To our best knowledge, this is the first experimental demonstration that corrosion rates of the Fe-based alloys in molten MgCl2-KCl-NaCl salt at 700 °C can be controlled below the target (15 µm/year) proposed by the US Department of Energy (DOE). Using affordable Fe-based alloys as main structural materials, the cost of chloride-TES (27 USD/kWh) could be comparable to that of commercial nitrate-TES (20–33 USD/kWh). Taking advantage of chloride-TES with higher operating temperature, the next-generation CSP plant could use an advanced power cycle (e.g., sCO2 Brayton) to have a much higher energy conversion efficiency, leading to a significantly lower Levelized Cost of Electricity (LCOE) than the current commercial CSP plant.

Diametral deviation and tool wear analysis in EDM of Fe-based shape memory alloy: An experimental study with microstructural analysis and advanced optimization

Shape memory alloys (SMAs) are an excellent choice for industrial applications such as orthopedic implacers, actuators, micro-tools, fitting and screening elements, aircraft components, military instruments, fabricating elements, and bio-medical devices, among others. Despite their remarkable characteristics, effective production of these alloys continues to be a problem for researchers worldwide. This paper has been aimed to examine the considered machining responses that is, tool wear rate (TWR) and diametral deviation (DD) in electrical discharge machining (EDM) of Fe-based shape memory alloy (SMA) using a Cu-electrode under the varying settings of input factors namely as; pulse on time (Ton), pulse off time (Toff), peak current (Ip), and gap voltage (GV). The central composite design matrix has been employed for planning the main runs. The experimental results reflect the lowest and highest for TWR as; 0.0694 and 0.1357 g/min; and for DD as; 0.02 and 0.19 mm, respectively. The microstructure analysis of the EDMed work samples and electrode surfaces have also been conducted using scanning electron microscopy (SEM). The micrographs exposed the development of debris, craters, micro-cracks, and recast layer creation on the workpiece surface and electrode tool as well. The creation of debris develops as a result of large spark energy at the work piece-tool contact as a result of a high peak current and long pulse on time. Furthermore, single and multi-objective optimization of investigated responses (i.e. TWR and DD) were tried using the desirability approach, Genetic Algorithm (GA), and teacher learning based optimization (TLBO), techniques. The obtained multi-response optimized values for TWR and DD by using desirability approach, Genetic algorithm (GA), and Teacher Learning Based Optimization (TLBO) are as; 0.0815 g/min and 0.0527 mm; 0.1529 g/min and 0.2547 mm; 0.1675 g/min and 0.2533 mm., correspondingly.

Effect of Zr/B ratio on β relaxation, structural heterogeneity, and magnetic properties of Fe-Zr-B amorphous alloys

Dynamic relaxation is an universal feature in amorphous alloys. However, few studies have been conducted on β relaxation of Fe-based amorphous alloys as most of them have insignificant β relaxation characteristics. In this work, the variation in β relaxation, structural heterogeneity, and soft magnetic properties are investigated in Fe-Zr-B amorphous alloys with pronounced β relaxation. β relaxation and structural heterogeneity are characterized by the ratio of β and α relaxation temperature (i.e., Tβ/Tα) and correlation length, respectively. With the increase of Zr/B ratio, the value of Tβ/Tα and the correlation length tend to decrease. Alloys with easily activated β relaxation or more heterogeneous structure possess poor soft magnetic properties, i.e., a significant reduction in saturation magnetic flux density and an increase in coercivity.

Deformation Mechanism Transition in Additively Manufactured Compositionally Graded Fe-Base Alloys

Deformation Mechanism Transition in Additively Manufactured Compositionally Graded Fe-Base Alloys

Carburization susceptibility of chromia-forming alloys in high-temperature CO2

It is generally believed that when a chromia scale forms in high-temperature CO2 environments, carbon uptake of alloys is nearly eliminated, thereby preventing carburization and associated degradation of properties. Herein we quantitively assess this notion through careful examination of several chromia-forming Ni-based and Fe-based commercial alloys after long-term (10,000-h) exposures to CO2 and air at 700 °C. Small but measurable carbon uptake ensued independent of alloy base metal (Ni/Fe), alloy crystal structure (FCC/BCC), and chromia growth rate. The rate for Ni-based alloys was strongly dependent on Si and Mn content, highlighting the need to understand possible long-term effects on mechanical properties.

Material constitutive modelling of Fe-based, Ni-based and high-entropy alloys: Development of Simu-Mat 1.0

Material constitutive modelling of Fe-based, Ni-based and high-entropy alloys: Development of Simu-Mat 1.0

Dealloying of Ni- and Fe-Based Alloys in Boiling Caustic Environments and the Parameters Influencing the Geometry of a Dealloyed Layer

Nickel alloys and stainless have been the material of choice for a wide range of industrial applications like power and petrochemical plants that involve exposure to corrosive environments. For instance, Alloy 800 (Fe-30Ni-20Cr) has been used as the tubing material in CANDU and Siemens steam generators (SGs) for decades with excellent in-service performance. However, despite their good resistance to general to localize corrosion, Ni- and Fe-based alloys are susceptible to environmentally assisted cracking (EAC) in certain environments, such as hot caustic aqueous solutions. Laboratory experiments have shown that these materials are susceptible to dealloying in hot caustic environments due to the selective removal of Fe, Cr and Mo (less noble elements). As a result of dealloying, a brittle nanoporous film forms on the surface that is enriched in Ni (the more noble element). This film has been proposed to act as a precursor to stress corrosion cracking (SCC) by a film-induced cleavage (FIC) mechanism, where the brittle film injects a high speed/energy crack to the substrate material.The fast kinetics of dealloying requires a connected percolating pathway of less noble element atoms to exist within the alloy that extends from the surface into the material. The presence of this pathway depends on the composition of the alloy. The parting limit defines the minimum amount of the more reactive element(s) in a particular alloy system that makes it susceptible to dealloying. Below the parting limit composition, dealloying will be suppressed by surface diffusion of the more noble element, even at very oxidizing potentials, and the surface of the material will show a passive-like behavior (general dissolution would eventually occur at high anodic overpotentials). Besides the alloy composition, dealloying highly depends on the electrode potential. Below a threshold potential (dealloying critical potential), surface diffusion of the more noble element will overcome the dissolution of the less noble element(s) and suppress dealloying.In this study, we examine different factors that affect dealloying and the geometry of a dealloyed layer through electrochemical measurements and nano-scale characterization techniques. Several engineering Ni- and Fe-based alloys were tested in deaerated boiling caustic solutions to understand the effect of alloy composition on the susceptibility to dealloying. Results indicate that an increase in Ni content will shift the dealloying critical potential to more positive potentials and subsequently the resistance to dealloying. Although Ni is the alloying element that provides nobility and resistance in hot caustic environments, our results show that the thermodynamic and kinetic behaviour, and the content of the less noble elements play an important role in these environments. A comparison between different alloys with similar Ni-content but different Cr and Mo contents shows the beneficial and detrimental role of Cr and Mo in dealloying, respectively. The air-formed chromia-based oxide on the surface of alloys with high Cr-content slowly dissolves in the caustic environment, delays the dissolution of less noble elements, and increases the resistance to dealloying.Changes in electrode potential and time of exposure to the caustic environments, alter the geometry of the dealloyed layer. Results show an increase in the diameter and coarsening of ligaments with increasing time of exposure to the caustic environment. Coarsening of ligaments is believed to impair the ability of a dealloyed layer to inject a micro-crack to the underlying material and initiate SCC. Also, results show that an increase in anodic overpotential of only a few millivolts in the vicinity of dealloying critical potential would change the geometry of the dealloyed layer significantly. The surface diffusion of the more noble element (i.e. Ni) cannot keep up with the fast removal of atoms of the less noble elements (i.e. Cr, Mo, and Fe) at more positive electrode potentials compared to the dealloying critical potential which results in a weak bonding at the film/metal interface. The weak bonding may not be able to support the transmission of a high-speed crack to the substrate material, reducing the likelihood of SCC initiation. Figure 1

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Effect of Cryogenic Thermal Cycling on Tribocorrosion Performance of Fe-Based Bulk Amorphous Alloy in 3.5 Pct NaCl Solution

Magnetic Migration Delays in Fe-Based Amorphous Alloys

Magnetic Migration Delays in Fe-Based Amorphous Alloys

Excellent magnetic softness-magnetization synergy and suppressed defect activation in soft magnetic amorphous alloys by magnetic field annealing

Fe-based amorphous alloys with high saturation magnetic flux density (Bs) are increasingly attractive from both scientific and technological points of view, however, they usually suffer from the trade-off between magnetization and softness. In this work, we explore the soft magnetic properties (SMPs), magnetic and atomic structures, and defect activation during creep deformation of as-quenched and annealed Fe82.65-xCoxSi2B14Cu1.35 (x = 0–20) amorphous alloys (AAs). Improved magnetic softness-magnetization synergy has been realized in all these alloys by field annealing. Particularly, superb SMPs with super-high Bs of 1.86 T, low coercivity of 1.2 A/m and high effective permeability of 16300 are obtained in the Fe66.65Co16Si2B14Cu1.35 AA. The locally regularized arrangement of domains, homogenized structure with less structural/magnetic defects and suppressed crystal-like ordering by field annealing contribute synergistically to the superb SMPs. Besides, the relaxation time spectra obtained from creep deformation indicate less liquid-like and solid-like defects activated in the field-annealed AA, which is correlated with the structural homogenization and superb SMPs. This work provides new and comprehensive insight into the interplay among external field, heterogeneous structure, SMPs and defect activation of Fe-based AAs, and offers a promising pathway for softening amorphous alloys with high Bs.