Iron-based Alloys Research Articles

Cyclic behavior of iron-based shape memory alloy bars for high-performance seismic devices

As a new member of the shape memory alloy (SMA) material family, iron-based SMAs (Fe-SMAs) show great potential in seismic applications due to their favorable properties. The thermomechanical behavior of Fe-SMAs has been extensively studied over the past decades. However, the relevant research regarding the use of Fe-SMAs in the community of earthquake engineering is still in an early stage, particularly on their mechanical behavior under cyclic tension–compression loadings. This study conducted a systematic experimental investigation of the cyclic behavior of Fe-SMA bars with a buckling-restrained device, which was cyclically tested under tension–compression loadings. The cyclic properties, such as hysteretic response, recovery capability, fatigue behavior, and fracture behavior were evaluated with varying strain amplitudes and different loading protocols. Test results show that satisfactory hysteretic loops with excellent deformation capability are obtained under cyclic tension–compression loadings. Fe-SMA bars exhibit acceptably stable behavior under multistage loadings. Moreover, they possess unique inherent properties, including moderate shape memory effect, high “post-yield” stiffness, and excellent fatigue behavior, thereby providing a promising solution to develop high-performance seismic devices. These properties are conducive to limit peak drifts, mitigate residual drifts of structures, and withstand long-duration ground motions and strong repeated aftershocks.

Research on the microstructure and properties of iron-based amorphous alloy/Al micro-laminated composites by vacuum hot pressing method

The connection of iron-based amorphous alloy ribbons and Al foil with multilayer structure was achieved by the vacuum hot-pressing diffusion bonding. The interface and the microstructure were analyzed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The results show that the amorphous ribbons crystallize, the hardness increases, and the intermetallic compounds are formed between layers. The laminated materials with multi-phase and multi-performance gradient structure, have high degree of microstructure controllability and designability. As the diffusion time increases, the impact toughness and bending strength of the laminated materials increase at first and then decrease. The impact absorption energy is negatively correlated with the thickness ratio of raw material (aluminum layer: amorphous layer), and the maximum impact absorption energy can reach 50 J. However, the bending strength is positively correlated with the thickness ratio, and the maximum bending strength can reach 341 MPa.

Impact-abrasive wear of martensitic steels and complex iron-based hardfacing alloys

Highly loaded wear components in manifold applications such as sieves, crushers, etc. suffer from combined impact and abrasive wear. To gain deeper understanding of different ongoing mechanisms, four different Fe-based materials, two martensitic steels Hardox 450 and Hardox 600, and two gas metal arc welded (GMAW) hardfacings - a Fe–Cr–C based hardfacing and a complex-alloyed Fe–Cr–Nb–C–B alloy were investigated with a novel modification of a cyclic impact and abrasion test. This test rig uses quartz sand as abrasive and a plunger simulating industrial sieving applications. Pre- and post-test materials analyses were performed utilising 3D microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), microhardness and nanoindentation tests for a thorough materials analysis and the clarification of the main occurring damaging mechanisms.Results indicate a very beneficial performance of a complex-alloyed Fe–Cr–Nb–C–B alloy due to its fine-dispersed hard phases and their homogenous distribution throughout the material, which does not change much with varying deposition parameters. In comparison, higher wear rates of a hypereutectic Fe–Cr–C alloy are attributed to coarse precipitated Cr-carbides within the microstructure. At martensitic steels, mechanically mixed layer were formed in the impact-abrasion region, which decreases the wear attack to a certain extent. However, massive materials displacement and abrasive wear occurs due to the lack of hard phases and high ductility, which obstruct increased abrasive attack.

Stretchable carbonyl iron powder/polydimethylsiloxane composites for noise suppression in gigahertz bandwidth

Electromagnetic (EM) noise interference in high-frequency communication systems has attracted considerable attention. Flake-shaped iron-based alloy powder–polymer composites are the conventionally used EM noise suppressors; however, they exhibit low stretchability and cannot effectively suppress EM noise in the range of several gigahertz. The present study demonstrated the application of carbonyl iron powder (CIP)/polydimethylsiloxane (PDMS) composites as EM noise suppressors at 1–18 GHz. The CIP/PDMS composites presented excellent mechanical properties (rupture strength 6.57 MPa, elongation 71%) even at the maximum CIP content of 40 vol%. The tensile test results and finite element method (FEM) simulations revealed a lowering of the elongation with CIP loading content, which was attributed to the localized stress at the agglomerated CIPs. The spherical CIPs exhibited multicore shell interface structures with 2–300 nm ring gaps that were larger than the skin depth of pure iron. EM absorption characterization revealed that the magnetic loss tangent at 10 GHz increased linearly with increasing CIP content. Furthermore, the power loss at 10 GHz for the 40 vol% CIP/PDMS composite was 2.25 times higher than that for the 20 vol% CIP/PDMS composite. This indicated the effective suppression of EM noise in the gigahertz bandwidth with the addition of CIP.

Study on the Physical Properties of Split-type Iron Base Shape Memory Alloy Pipe Joint

Aiming at the leakage phenomenon of pipeline system due to corrosion and other reasons, a split type iron-based shape memory alloy pipe joint based on the button bond connection was designed for repair. This split-type pipe joint can be used for quick in-situ maintenance of pipelines without cutting off pipelines or stopping transmission without pressure relief. It is especially suitable for intensive pipeline maintenance and online emergency maintenance. In order to study the connection performance of the split iron-based shape memory alloy pipe joint, this paper took the Fe17Mn4Si10Cr4Ni alloy pipe joint as the research object, and carried out pressure sealing and pull-out experiments respectively on the integral pipe joint and the split pipe joint which had not been carried out and had been subjected to one heat and mechanical training. The results showed that, compared with the integral pipe joint, the pressure seal value of the split pipe joint decreased by 40% to 20MPa and the pulling force decreased by 48.9% without heat-mechanical training. However, after 1 time of thermal-mechanical training, the pressure sealing value of the split-type pipe joint decreased by 12.5% to 32MPa and the pulling force decreased by 21.2% compared with the integral pipe joint. It can be seen that thermal-mechanical training can significantly improve the joint performance of split pipe joints, and the split pipe joint can meet the requirements of medium and low pressure pipeline connection and maintenance.

Fabrication, simulation, and characterization of planar inductors

A planar inductor with excellent magnetic characteristics was successfully prepared by screen printing high solid content iron-based alloy magnetic pastes onto copper-clad laminates (CCL). The sample was then cold-isostatic pressed (CIP) to increase the packing density. To solve the problems of low electrical resistivity and low power handling capability of alloy powders for power inductor applications, an epoxy resin vehicle was added to form an insulating layer on top of the iron-based alloy powder surfaces and distribution gaps between the alloy powders. A central column was formed by punching in the center of the planar inductor and filled with magnetic paste to increase the inductance, magnetic flux channeling, and storage energy. A planar inductor 8.5 mm × 7.0 mm× 0.4 mm in size with an inductance value of about 2.7 μH at 1 MHz, a quality factor of 10–13, and inductance decline rate of about 5% at a DC bias of 2.5 A can be successfully prepared using the proposed method. A 3D electromagnetic field finite element analysis tool (ANSYS Maxwell R19.3) was used to simulate the coil geometry and magnetic paste formulation effects on the magnetic flux density distribution, and the planar inductor electromagnetic properties to identify the optimal parameters. The differences between the simulation and the experimental planar inductor DC-bias superposition characteristics were compared. The deviations between the measured and simulated results are only within 6%, suggesting that the simulation has very high accuracy and reliability.

ON THE EFFICIENCY OF ULTRASONIC IMPACT IN THE HOT-DIP ALUMINIZING OF IRON-BASED ALLOYS

It has been experimentally proven that the effect of ultrasound on the melt during hot-dip aluminizing does not affect the phase composition of the diffusion zone formed as a result of heterogeneous reactions at the interface between aluminum and iron-based alloys. It is shown that at a fixed temperature, the frequency of supplied acoustic vibrations of 18-20 kHz and an amplitude of 10-15 μm, the thickness of the coating and diffusion zone decreases by 30-50 %.

Shape Memory Properties and Microstructure of New Iron-Based FeNiCoAlTiNb Shape Memory Alloys

The shape memory properties and microstructure of Fe41Ni28Co17Al11.5(Ti+Nb)2.5 (at.%) cold-rolled alloys were studied at the first time using the values reported in constant stress thermal cycling experiments in a three-point bending test. Thermo-magnetization curves of 97% cold-rolled and solution-treated sample aged at 600 °C for 24, 48 and 72 h showed evidence of the martensitic transformation, and the transformation temperatures increased their values from 24 to 72 h. The alloy cold-rolled to 97% and then solution-treated at 1277 °C for 1 h showed that most grains were aligned near <100> in the rolling direction in the recrystallization texture. The intensity of texture was 13.54, and an average grain size was around 400 μm. The sample aged at 600 °C for 48 h showed fully recoverable strain up to 1.6% at 200 MPa stress level in the three-point bending test. However, the experimental recoverable strain values were lower than the theoretical values, possibly due to the small volume fraction of low angle grain boundary, the formation of brittle grain boundary precipitates, and a grain boundary constraint lower than the expected intensity of texture in the samples.

Room-temperature wear resistance of tungsten carbide composite layers produced on grey cast iron by diffusion-controlled in situ reactions

To improve the tribological properties of substrate surfaces, tungsten carbide composite layers were deposited on an iron-based alloy by diffusion-controlled in situ reaction (DIR) at different temperatures. The microstructure, phase composition and worn morphology of the composite layer were characterized by utilizing scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD) and confocal laser scanning microscopy (CLSM). A thin tungsten carbide layer with an interface crack was obtained at 1000 °C. At 1100 °C, the structure of the optimized composite layer contains a thin tungsten plate, a thicker tungsten carbide layer (300 μm) and a broad composite zone (2.5 mm) from top to bottom. The indexed phase composition for the carbide layer includes WC and α-Fe, and the composite zone consists of α-Fe, Fe6W6C, FeC and graphite. The tribological properties and mechanical properties of the composite layers were evaluated by using a ball-on-disk tribometer and a nanoindentation hardness tester. The average nanohardness of the tungsten plate, carbide layer, composite region and substrate is approximately 6.4 ± 1.0 GPa, 24.1 ± 3.4 GPa, 13.5 ± 2.4 GPa and 9.6 ± 1.2 GPa, respectively. Friction wear tests of all samples against GCr15 balls were performed at room temperature under 5, 10, 15 and 20 N normal loads. The carbide layer exhibits an average coefficient of friction of 0.39–0.63, which is higher than that of the substrate under an identical load due to the lubricating effect of the flake graphite phase in the substrate during the wear process. The specific wear rate of the carbide layer with a value of 2.69–4.33 is 18.5–34.3% of that of the substrate. The results of the worn morphology presence of particle deformation, extraction and crushing reveal that abrasive wear is a dominant abrasion mechanism for the carbide layer. For the substrate, adhesive wear plays an important role and is accompanied by abrasive wear.

Surface processing for iron-based degradable alloys: A preliminary study on the importance of acid pickling

The formation of a heterogeneous oxidized layer, also called scale, on metallic surfaces is widely recognized as a rapid manufacturing event for metals and their alloys. Partial or total removal of the scale represents a mandatory integrated step for the industrial fabrication processes of medical devices. For biodegradable metals, acid pickling has already been reported as a preliminary surface preparation given further processes, such as electropolishing. Unfortunately, biodegradable medical prototypes presented discrepancies concerning acid pickling studies based on samples with less complex geometry (e.g., non-uniform scale removal and rougher surface). Indeed, this translational knowledge lacks a detailed investigation on this process, deep characterization of treated surfaces properties, as well as a comprehensive discussion of the involved mechanisms. In this study, the effects of different acidic media (HCl, HNO3, H3PO4, CH3COOH, H2SO4 and HF), maintained at different temperatures (21 and 60 °C) for various exposition time (15–240 s), on the chemical composition and surface properties of a Fe–13Mn-1.2C biodegradable alloy were investigated. Changes in mass loss, morphology and wettability evidenced the combined effect of temperature and time for all conditions. Pickling in HCl and HF solutions favor mass loss (0.03–0.1 g/cm2) and effectively remove the initial scale.

Iron-Based shape memory alloy for strengthening of 113-Year bridge

This study focuses on the large-scale application of a Fe-Mn-Si shape memory alloy (Fe-SMA) for strengthening a historic roadway bridge in Petrov nad Desnou (113-years), Czech Republic. To the best of the authors’ knowledge, this is the first application of an iron-based SMA (Fe-SMA) for prestressed strengthening of a bridge. In this study, the shape memory effect (SME) of the Fe-SMA was used for the prestressed strengthening of bridge girders. A mechanical anchorage system was developed to apply multiple Fe-SMA strips to the steel girders of the bridge subjected to daily passengers and heavy trucks. The SME of the Fe-SMA was activated by heating to approximately 260 °C using ceramic heating pads. The test results showed that the recovery stress of the Fe-SMA strips resulted in a compressive stress of approximately –33 MPa in the lower flange of the bridge girder. This compressive stress significantly increased the yield and fatigue capacity of the strengthened girder. Before and after the strengthening, the bridge was loaded with a 45-ton crane to assess the efficiency and performance of the system. Laboratory experiments were performed to optimize the mechanical anchors and examine the feasibility of the proposed strengthening method prior to application to the bridge. Finally, long-term monitoring of the prestressed Fe-SMA plates after installation on the bridge was conducted. The results showed that the main loss of the prestressing force caused by relaxation occurred within the first 30 days after activation and was approximately 20% of the original prestress.

Structure and Magnetic Properties of Fe-B-La-Al Alloy

Nanocrystalline magnetic materials are of great interest in order to meet the needs of electronics and electrical engineering. There are many possibilities to modify the synthesis parameters and chemical composition in order to obtain the most desirable magnetic properties and microstructure. The paper discusses an iron-based alloy with the addition of boron lanthanum and aluminium. The alloy was obtained by induction melting and casting with a melt-spinner. The main purpose of the work was to analyze the structure and properties of both the starting alloys in the form of ingots and the obtained tapes. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration magnetometry (VSM) and microhardness measurements using the Vickers method were carried out.

Influence of Various Heat Treatments on Hardness and Impact Strength of Uddeholm Balder: Cr-Mo-V-Ni Novel Steel Used for Engine Construction.

The construction of an engine requires optimized geometry and superb material properties in various environments. Tensile and yield strength are not the only parameters essential to consider. Hardness, impact toughness, and ductile-brittle transition temperature (DBTT) are also crucial. In this paper, Balder, Chromium-Molybdenum-Vanadium-Nickel steel with low impact toughness attested is considered. It contains both high Nickel and high Vanadium content, a rare combination among iron-based alloys. This study aims at proving that conventional heat treatment can improve its impact toughness while maintaining hardness level, exceeding its to-date performance. Steel’s exact elemental composition was checked, and material samples’ hardness and impact toughness were measured. Four heat treatments were proposed, then hardness and impact toughness were measured again. It was established that impact toughness over three times higher than marketed (57.3 J against 17 J) can be achieved with simultaneous 2 HRC points (from 46.4 HRC to 48.4 HRC) rise in hardness. Achieved parameters place examined alloy at the high-ranking position among similar steels. Occurrence of temper embrittlement was avoided. Notably, the ductile-brittle transition was not observed in any sample.

Research on the structure-activity relationship of Fe-Cr alloy in marine environment based on synchrotron radiation: Effect of Cr content

A solid-liquid interface will form on the surface of metal materials when immersed in the marine, which determines the corrosion resistance. Alloying is one of the most effective approaches to protect materials from corrosion failure by tuning the structure-activity relationship of the solid-liquid interface. Chromium is the decisive element in determining the corrosion resistance of iron-based alloys because it can increase electrode potential and promote passivation. However, up to date, the effect of chromium on materials service safety has not been adequately validated, which restricted the precise design and application of the corrosion resistance alloys. Herein, we probed the effect of Cr on structure-activity relationship with multiple characterization means including electrochemistry, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), surface enhanced Raman spectroscopy (SERS), synchrotron radiation grazing-incidence X-ray diffraction (GIXRD), and X-ray absorption fine structure (XAFS). The solid-liquid interface is mostly amorphous, with some nanocrystals. The addition of Cr can promote the increase of FeOOH and formation of FeCr2O4, with first increase and then decrease of Cr2O3. The enrichment of FeOOH and Cr2O3 improves corrosion resistance when Cr content is less than 30 wt.%. The formation of FeCr2O4 leads to the transformation from corrosion products to passive film when Cr content exceeds 18 wt.%. In addition, the lack of Cr2O3 and the formation of FeCr2O4 result in the descend of corrosion resistance at 40 wt.% Cr content.

Dual-metal laser powder bed fusion of iron- and cobalt-based alloys

A dual-metal laser powder bed fusion (LPBF) of cobalt-chrome‑molybdenum-based superalloy and maraging steel has been carried out using an EOS M290 machine. The ideal orientations of the dual-metal material were established using an electron backscatter diffraction (EBSD) technique. Three sections were analyzed: a) the cobalt-based alloy area, b) the iron-based alloy area, and c) the interface between the iron- and cobalt-based alloys. A strong 〈110〉||building direction (BD) fiber texture dominates the cobalt-based material, while the iron-based alloy exhibits 〈111〉||BD and 〈100〉||BD fiber textures. The texture in the interface changes from 〈100〉||BD at the bottom of the interface (close to maraging steel section) to <110>||BD at the top section (near the cobalt-chrome‑molybdenum-based superalloy section). Moreover, the diffusion calculations suggest a negligible diffusion depth in the interface, which avoids any possible formation of detrimental intermetallics. The information from this work can be utilized to control the texture of the dual-metal LPBF material to optimize various physical and mechanical properties while ensuring that no unwanted solid solution alloying takes place along the interface.

Thermally-activated shape memory alloys for retrofitting bridge double-angle connections

Double-angle connections are prone to fatigue cracking in old steel bridges; however, owing to their complexity, there are not many retrofitting solutions for these details. This study proposes a retrofitting system for double-angle connections using iron-based shape memory alloys (Fe-SMAs). An innovative connection test setup equipped with an optical 3D digital image correlation (DIC) measurement system was developed. The retrofitting system included two end-anchorages set on either side of the connection. Fe-SMA strips were inserted inside the anchorages, and then were thermally activated (pre-stressed) to a temperature of 260 °C. Numerical finite element studies were performed to investigate the static behavior of the system. It was found that the activated/prestressed Fe-SMA strips not only apply a reverse positive moment on the connection (versus an undesirable negative fixity moment), but also “absorb” a portion of the negative moment, owing to the added axial stiffness. The proposed SMA-based system offers a versatile and cost-effective technique (with quick and easy installation) for bridge connections, and can significantly reduce the effects from undesirable sources of fatigue cracking.

Hydrogen Atom and Molecule Adsorptions on FeCrAl (100) Surface: A First-Principle Study

FeCrAl alloys are promising accident-tolerant fuel (ATF) cladding materials for applications in light water reactors (LWRs). Despite the excellent mechanical and antioxidation properties, this series of iron-based alloys has poor hydrogen embrittlement (HE) resistance due to the strong hydrogen uptaking ability. The hydrogen embrittlement effect can cause the degradation and premature failure of the material, and this effect can be enhanced by the high-temperature/high-pressure/high-irradiation environment in reactors. So, the potential danger should be taken seriously. In this paper, we have studied the hydrogen atom and molecule adsorptions on both Fe (100) and FeCrAl (100) surfaces to discover how the hydrogen atom and molecule (H/H2) interact with the Fe and FeCrAl (100) surface in the first place. The results show that there are strong element effects on the FeCrAl surface. The Al atom itself has no interaction with hydrogen. When the Al atom is beside the Fe atom, this Fe atom has a slightly lower interaction with hydrogen. However, the Al atom beside the Cr atom will enhance the hydrogen interaction with this Cr atom. On the other hand, when the Cr atom is beside the Fe atom, these two atoms (Fe–Cr bridge site) can reduce the interactions with H. In addition, when two Cr and two Fe atoms together make a four-fold site (FF site), the two Cr atoms can increase the interaction of the two Fe atoms with H. The element effects discovered can be a good guide for making hydrogen prevention coatings.

Modification of fuel performance code to evaluate iron-based alloy behavior under LOCA scenario

Accident tolerant fuels (ATF) has been studied since the Fukushima Daiichi accident in the research efforts to develop new materials which under accident scenarios could maintain the fuel rod integrity for a longer period compared to the cladding and fuel system usually utilized in Pressurized Water Reactors (PWR). The efforts have been focused on new materials applied as cladding, then iron-base alloys appear as a possible candidate. The aim of this paper is to implement modifications in a fuel performance code to evaluate the behavior of iron-based alloys under Loss-of-Coolant Accident (LOCA) scenario. For this, initially the properties related to the thermal and mechanical behavior of iron-based alloys were obtained from the literature, appropriately adapted and introduced in the fuel performance code subroutines. The adopted approach was step by step modifications, where different versions of the code were created. The assessment of the implemented modification was carried out simulating an experiment available in the open literature (IFA-650.5) related to zirconium-based alloy fuel rods submitted to LOCA conditions. The obtained results for the iron-based alloy were compared to those obtained using the regular version of the fuel performance code for zircaloy-4. The obtained results have shown that the most important properties to be changed are those from the subroutines related to the mechanical properties of the cladding. The results obtained have shown that the burst is observed at a longer time for fuel rods with iron-based alloy, indicating the potentiality of this material to be used as cladding with ATF purposes.

Research Progress of Preparation and Interfacial Reaction of Ceramic Particles Reinforced Iron-Based Alloy

Ceramic particle reinforced iron-based alloys have been widely used in aerospace, land transportation and other aspects, so it has attracted tremendous attention. Aiming at the preparation and interfacial reaction of ceramic particle reinforced iron-based alloys, the preparation methods for interfacial reactions, reinforcement selection and design of ceramic particle reinforced iron-based alloys are introduced in this paper. Combined with the recent studies on ceramic particle reinforced iron-based alloys, this paper focuses on the ceramic particle reinforced iron-based interface and strengthening models/mechanisms, based on existing research, prospects for further ceramic particle reinforced iron-based alloys were studied.

Superior low-cycle fatigue performance of iron-based SMA for seismic damping application

This study reveals the superior low-cycle fatigue performance of iron-based shape memory alloy (Fe-SMA) for seismic damping application, catering to the need for more durable, resilient, and perhaps fatigue-free structural systems in seismic active regions. The study commences with material tests examining both the macroscopic and microscopic properties of Fe-SMA under monotonic and cyclic loading, followed by calibration of combined hardening parameters to facilitate numerical modelling. A Fe-SMA shear damper specimen is tested, and its behavior is compared with its mild steel counterpart. Among other findings, the study revealed good ductility of Fe-SMA with a fracture strain of up to 55% under monotonic loading. The fatigue life of Fe-SMA is from 4007 to 83 when the strain amplitude increases from ±1% to ±9%, and the values could be 10 times that of common structural steel. The cyclic strain-life relationships of Fe-SMA can be readily presented by the conventional Basquin-Coffin-Manson relationship. Both kinematic and isotropic hardening characteristics of Fe-SMA are observed, and a combined kinematic/isotropic hardening model with calibrated parameters is shown to adequately capture the hysteretic behavior of the material. The subsequent damper tests provide further evidence of its superior fatigue performance, where a fatigue life of 173 cycles is observed for the Fe-SMA damper under a constant rotational angle of 4%, in contrast to 16 cycles for its normal steel counterpart. The unique phase transformation characteristic of Fe-SMA could also affect the fatigue failure mode, where different crack patterns are observed for the dampers with the different materials.