Fe-based Alloys Research Articles

Numerical Study of RC Beams Strengthened with Fe-Based Shape Memory Alloy Strips Using the NSM Method

This paper presents a finite element (FE) analysis for predicting the flexural behavior of reinforced concrete (RC) beams strengthened with Fe-based shape memory alloy (Fe-SMA) strips using a near surface mounted (NSM) method. Experimental results reported in the literature were used to verify the proposed FE model. FE analyses were conducted using OpenSees, a general-purpose structural FE analysis program. The RC beam specimens were modeled using a nonlinear beam-column element and a fiber element. The Concrete 02 model, Steel 01 model, and Pinching 04 model were applied to the concrete, steel reinforcement, and Fe-SMA strip in the fiber element, respectively, and the FE analysis was carried out in a displacement control method based on the Newton-Raphson method. The FE model of this study accurately predicted the initial crack load, yield load, and ultimate load. From parametric analyses, it was concluded that an increase in the compressive strength of the concrete increases the ductility of the specimen, and an increase in the level of recovery stress on the Fe-SMA strip increases the initial stiffness of the specimen.

Functional 3D nanoporous Fe-based alloy from metallic glass for high-efficiency water splitting and wastewater treatment

Fe-based alloys with 3D nanoporous structures (np-Fe) are promising catalysts in various fields. In this study, np-Fe is easily fabricated using Fe-based metallic glass (Fe-MG) ribbons to prepare Fe-based nanocrystalline alloys as precursors after chemical dealloying in an HCl solution. The potential applications of np-Fe in energy conversion and environmental remediation are highlighted by oxygen evolution reaction (OER) and dyeing wastewater treatment of an np-Fe800-12h. The results show that np-Fe has excellent OER performance with an overpotential of 230 mV at a current density of 10 mA cm−2. Moreover, np-Fe exhibits superior degradation capability toward azo dye pollutants and shows improved performance than even its nanocrystalline precursor and Fe-MG. This study thus paves a new avenue for fabricating the desired np-Fe as high-performance catalysts for energy conversion and wastewater treatment applications.

Inhibition of metal dusting corrosion on Fe-based alloy by combined near surface severe plastic deformation (NS-SPD) and thermochemical treatment

Combined NS-SPD and thermochemical treatment has been used to improve the metal dusting corrosion resistance of Incoloy 800. After testing under infinite carbon activity for 20−100 h, carbon was not found in the NS-SPD region while corrosion products formed in the non-NS-SPD region. The improved resistance is a result of the NS-SPD yielding a high density of defects in the deformation zone that developed into an ultra-fine-grained structure near the surface during the subsequent thermochemical treatment. These microstructural changes increase the effective diffusion coefficient for Cr in the alloy, hence promoting the formation of a highly protective oxide scale.

Preparation of flake-shaped Fe-based nanocrystalline soft magnetic alloy particles subjected to plastic deformation

ABSTRACT Fe-based nanocrystalline alloy powder prepared by ball-milling is a potential candidate as a soft magnetic composite (SMC). Since the magnetic properties of particles having a random geometry arising from brittle fracture deteriorate by the presence of a demagnetising field, plastically deformed flake-shaped powders, exhibiting better magnetic properties on account of the suppression of any demagnetising field, are desirable. Microstructure such as grain size, lattice distortion and the distribution of dislocations, are affected by ball-milling treatment which changes the magnetic properties. In this study, Fe-based nanocrystalline alloy sheets are ball-milled with lubricant oil as a process control agent (PCA) and the microstructure of the particles investigated. The PCA effectively suppresses the brittle fracture of the alloy sheet during the ball-milling treatment and plastically deformed flake-shaped particles are then successfully obtained. Transmission electron microscopy reveals that there were few lattice defects in the α-Fe grain of the alloy, which indicated that almost only grain-boundary-mediated processes such as GB diffusion/sliding/migration and grain rotation dominate the deformation mechanism. However, Williamson–Hall analysis based on synchrotron radiation exhibits a slope indicating micro-strain in the α-Fe grains. It is found that the plastic deformation induced by the ball-milling treatment forms a microstructure having lattice distortion but containing few lattice defects. It is considered that a slight growth of the existing grains, which can be induced by thermal treatment, can achieve a strain- and dislocation-free microstructure, which is desirable for soft magnetic alloys.

Effect of La2O3 on microstructure and properties of Fe-based alloy coatings by laser cladding

One of the challenges limiting the application of laser cladded Fe-based coatings is the coarse columnar grains formed during the process. In order to improve the microstructure homogeneity of laser cladded coatings, Fe-based alloy (Fe78.5Cr15.6Ni4.0Si0.7) composite coatings with different La2O3 additions were prepared on the surface of 45-steel substrate by laser cladding. The effect of La2O3 content on the microstructure and properties composite coatings were systematically studied. X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze the phase structure and microstructural evolution of Fe-based alloy composite coatings, and the hardness and tribological properties were measured by the microhardness tester and ball on disc wear tester, respectively. The results show that the addition of La2O3 plays the role of grain refinement, and certain amount of addition can completely eliminate the coarse columnar grains. Due to the fine-grain strengthening and dispersion strengthening of La2O3, the hardness and wear resistance of Fe-based alloy composite coatings have been improved. Especially, when the content of La2O3 is 1 wt%, the hardness increases to 3.1 times and the wear loss decreases to 27.7%, compared with the substrate material. The wear surface of composite coating with 1 wt% La2O3 suffered minor damage, and the wear mechanism is slightly abrasive wear. In contrast, higher amount of 2 wt% La2O3 addition has less effective grain refining where some columnar grains appear on the interface, and the hardness and wear resistance of composite coatings decrease as well. Meanwhile, the wear mechanism is transformed into a mixed mode of abrasive wear and adhesive wear.

Six-Month Long In Vitro Degradation Tests of Biodegradable Twinning-Induced Plasticity Steels Alloyed with Ag for Stent Applications.

Twinning-induced plasticity (TWIP) Fe-Mn-C steels are biodegradable metals with far superior mechanical properties to any biodegradable metal, including Mg alloys, used in commercially available devices. For this reason, the use of Fe-Mn-C alloys to produce thinner and thinner implants can be exploited for overcoming the device size limitations that biodegradable stents still present. However, Fe-Mn steels are known to form a phosphate layer on their surface over long implantation times in animals, preventing device degradation in the required timeframe. The introduction of second phases in such alloys to promote galvanic coupling showed a short-term promise, and particularly the use of Ag looked especially effective. Nonetheless, the evolution of the corrosion mechanism of quaternary Fe-Mn-C-Ag alloys over time is still unknown. This study aims at understanding how corrosion changes over time for a TWIP steel alloyed with Ag using a simple static immersion setup. The presence of Ag promoted some galvanic coupling just in the first week of immersion; this effect was then suppressed by the formation of a mixed carbonate/hydroxide layer. This layer partly detached after 2 months and was replaced by a stable phosphate layer, over which a new carbonate/hydroxide formed after 4 months, effectively hindering the sample degradation. Attachment of phosphates to the surface matches 1-year outcomes from animal tests reported by other authors, but this phenomenon cannot be predicted using immersion up to 28 days. These results demonstrate that immersion tests of Fe-based degradable alloys can be related to animal tests only when they are carried out for a sufficiently long time and that galvanic coupling with Ag is not a viable strategy in the long term. Future works should focus more on surface modifications to control the interfacial behavior rather than alloying in the bulk.

Parametric investigation of tool wear rate in EDM of Fe-based shape memory alloy: microstructural analysis and optimization using genetic algorithm

PurposeThis study aims to experimentally investigate the influence of considered process parameters, i.e. pulse on time, pulse off time, peak current and gap voltage, on tool wear rate (TWR) in electrical discharge machining (EDM) of iron (Fe)-based shape memory alloy (SMA) through designed experiments. The parametric optimization for TWR has also been attempted using the desirability approach and genetic algorithm (GA).Design/methodology/approachThe response surface methodology (RSM) in the form of Box–Behnken design has been used to scheme out the experiments. The influence of considered process inputs has also been observed through variance analysis. The reliability and fitness of the developed mathematical model have been established with test results. Microstructure analysis of machined samples has also been evaluated and analyzed using a scanning electron microscope (SEM). SEM images revealed the surface characteristics such as micro-cracks, craters and voids on the tool electrode surface. SEM images provide information about the surface integrity and type of wear on the surface of the tool electrode.FindingsThe input parameters, namely, pulse on time and pulse off time, are major influential factors impacting the TWR. High TWR has been reported at large pulse on time and small pulse off time conditions whereas higher TWR is reported at high peak current input settings. The maximum and minimum TWR values obtained are 0.073 g/min and 0.017 g/min, respectively. The optimization with desirability approach and GA reveals the best parametric values for TWR i.e. 0.01581 g/min and 0.00875 g/min at parametric combination as pulse on time = 60.83 µs, pulse off time = 112.16 µs, peak current = 18.64 A and gap voltage = 59.55 V, and pulse on time = 60 µs, pulse off time = 120 µs, peak current = 12 A and gap voltage = 40 V, correspondingly.Research limitations/implicationsProposed work has no limitations.Originality/valueSMAs have been well known for their superior and excellent properties, which make them an eligible candidate of paramount importance in real-life industrial applications such as orthopedic implants, actuators, micro tools, stents, coupling, sealing elements, aerospace components, defense instruments, manufacturing elements and bio-medical appliances. However, its effective and productive processing is still a challenge. Tool wear study while processing of SMAs in EDM process is an area which has been less investigated and of major concern for exploring the various properties of the tool and wear in it. Also, the developed mathematical model for TWR through the RSM approach will be helpful in industrial revelation.

Structural and Magnetic Properties of P Microalloyed Fe76Cu0.8Nb2.2B9Si12 Alloys

The development of Fe-based nanocrystalline alloys with high saturation magnetization (Bs), excellent magnetic softness and good manufacturability is highly desirable. Here, the effect of substituting 1 at% P for B and Si on the thermal stability, microstructure and magnetic properties of Fe76Cu0.8Nb2.2B9Si12 alloy has been studied in detail. It was found that replacing B with P effectively reduces the coercivity (Hc) of the alloy without deteriorating the Bs and permeability (μ). However, replacing Si with P has little effect on the Hc and Bs, yet significantly reduces the μ. The variation in the magnetic properties can be well understood from the evolution of the microstructure and magnetic anisotropy induced by P microalloying. The Fe76Cu0.8Nb2.2B8Si12P1 alloy with a good processing window, a high Bs of 1.41 T, a great μ of 29,000 at 1 kHz and a low Hc of 0.6 A/m is suitable for high-power electronic devices.

Processing of Fe-Based Alloys by Detonation Spraying and Spark Plasma Sintering

Processing of Fe-Based Alloys by Detonation Spraying and Spark Plasma Sintering

Research on gradient additive remanufacturing of ultra-large hot forging die based on automatic wire arc additive manufacturing technology

In this paper, an automatic WAAM technology is proposed to realize the gradient additive remanufacturing of ultra-large hot forging dies. Firstly, a vertical additive manufacturing strategy and a normal additive manufacturing strategy are proposed to meet different additive manufacturing demands. Secondly, the basic principle of layering design of ultra-large hot forging dies is developed, and the wear resistance of Ni-based, Co-based, and Fe-based alloys at room temperature and high temperature is analyzed. The Co-based alloy has the best high-temperature wear resistance, which can be used on the surface of the hot forging die to strengthen the die. In order to control the forming quality of additive manufacturing, the relationship between welding parameters and weld shape was discussed, and the reverse system of welding process parameters was built. Finally, a typical aviation ultra-large hot forging die is selected as the research object. According to different stress and temperature distribution in different regions of the ultra-large hot forging die in service, materials with different properties are used in corresponding regions to improve the service life of the die, reduce the remanufacturing costs, and improve the remanufacturing efficiency. The experimental results show that the service life of the hot forging dies repaired by the automatic gradient function WAAM technology is significantly increased, the material is reduced by more than 50%, and the production efficiency is increased by more than 50%.

Study on a Novel Biodegradable and Antibacterial Fe-Based Alloy Prepared by Microwave Sintering.

This research produced a porous Fe-8 wt.% Cu alloy by microwave sintering in order to achieve (i) an increased biodegradation rate, and (ii) an antibacterial function. The Fe-8Cu alloy had higher density, hardness and degradation rate (about 2 times higher) but smaller and fewer surface pores, compared to the pure Fe. The Fe-8Cu alloy had a strong antibacterial function (the antibacterial rates against E. coli were up to 99.9%) and good biocompatibility. This work provides a novel approach of alloy design and processing to develop novel antibacterial Fe-based alloys.

High-temperature steam oxidation behavior of alumina-forming duplex FeNiCrAl and ferritic FeCrAl alloys at 800 °C to 1050 °C

Two alumina-forming Fe-based alloys, duplex FeNiCrAl (alumina-forming duplex stainless steel, ADSS) and ferritic FeCrAl (APM) alloys, were oxidized in steam at 800 °C to 1050 °C for up to 72 h. Formation of spinel oxides on ADSS resulted in larger weight gain than APM, while the highest weight gain was observed at 900 °C. Outer γ- and/or θ-alumina and inner α-alumina were formed on APM, whereas dispersed spinel oxides as well as γ- and α-alumina on ADSS. Similar alumina formation kinetics was observed for both alloys, while transient alumina formation resulted in faster kinetics at 900 °C.

Nanoscale Materials for State-of-the-Art Magnetic Memory Technologies

The review deals with different materials science aspects of state-of-the-art magnetic memory technologies, such as magnetoresistive random-access memory (MRAM), antiferromagnetic (AFM) memory, and skyrmion racetrack memory. Particularly, the materials with high perpendicular magnetic anisotropy (PMA), such as CoFeB, L10-ordered Mn- and Fe-based alloys, are considered (Sec. 1) regarding their applications in MRAM technology. Furthermore, studies of AFM alloys, such as FeRh, CuMnAs, Mn2Au, are reviewed (Sec. 2) with an emphasis on the application of these materials in AFM-memory technology. Finally, the last (3rd) section of the review is concerning materials that could be used in skyrmion racetrack memory.

Effect of Sintering Condition on Tensile Strength of Fe-based Non-equiatomic High Entropy Alloy

Effect of Sintering Condition on Tensile Strength of Fe-based Non-equiatomic High Entropy Alloy

The synergy of chromium and molybdenum on the stable catalysis of Fe-based amorphous alloy powder

The Fe41Co7Cr15Mo14C15B6Y2 amorphous alloy powder was prepared by gas atomization. It was interesting that rhodamine B can be completely degraded within only 6 min by 1 g/L Fe41Co7Cr15Mo14C15B6Y2 and 3 mM H2O2 at pH 5.0 at 313 K. This result can be repeated at least 30 times. It is worth mentioning that the catalyst surface spontaneously formed a double passivation film during the degradation process. The passivation film composed of Cr2O3 and Cr(OH)3 is located in the outer layer, while the passivation film composed of MoO2 and MoO3 is located in the inner layer. This double passivation film regulates the contact of ions on the catalyst surface with the solution, which makes the catalyst have a stable catalytic efficiency in the reaction. The findings have important implications in developing Fe-based amorphous alloys for functional application materials in the field of wastewater treatment.

Improved catalytic efficiency and stability by surface activation in Fe-based amorphous alloys for hydrogen evolution reaction in acidic electrolyte

The development of efficient and durable electrocatalysts for water splitting to produce hydrogen is of great significance to relieve the energy crisis. In this work, a self-supported FeMoPC amorphous catalyst with a sandwich structure prepared by the electrochemical activation-dealloying two-step method is reported. The catalyst exhibits a low overpotential of 96 mV at -10 mA cm−2, a Tafel slope of 51 mV dec−1, and excellent stability for over 16 h in 0.5 M H2SO4 solution for hydrogen evolution reaction (HER). The good catalytic activity is attributed to the nanoislands with rich active sites and large reaction areas for efficient HER obtained by an electrochemical cyclic voltammetry scan activation. Additionally, the formation of a compact protective phosphate/oxide layer that has high concentration of Mo on the surface during the subsequent dealloying enhances the durability of the catalyst. This work overcomes the issues associated with poor durability of Fe-based catalyst in acidic electrolyte and broadens the application of Fe-based amorphous alloys.

Effect of Annealing Temperature on the Soft Magnetic Properties of Fe<sub>70.43</sub>Nb<sub>10.77</sub>Si<sub>15.77</sub>Cu<sub>2.34</sub>B<sub>0.69</sub> Amorphous Aanostrips at 20K, 300K

Since Fe-based amorphous alloys are widely used in magnetic separators, sensors and other fields, it is of practical significance to carry out research on amorphous strips used in this field.The effects of annealing temperature on the soft magnetic properties of Fe70.43Nb10.77Si15.77Cu2.34B0.69 amorphous nanostrips with 25 μm and 28 μm thickness prepared by the single roll cold method were investigated at 20 and 300K.Five specimens were annealed at472.12K, 672.12K, 772.12K, 822.12Kand 872.12K, respectively, and their microstructure and magnetic properties were tested viametallographic microscopy, X-ray diffraction, and vibrating specimen magnetometer. At cryogenic temperatureof 20K, specimens annealed at 672,12K exhibited the best magnetic properties, including the coercive forceof8.1265A/m, saturation magnetic induction intensity of1.4351T,and its residual value of 0.2462T. The comparative analysis of experimental results obtained strongly indicates that the soft magnetic properties of the amorphous alloy are significantly improved by the particular annealing treatment.

Dielectric tensor circular anisotropy in Co- and Fe-based ferromagnetic alloys

Dielectric tensor circular anisotropy in Co- and Fe-based ferromagnetic alloys

Biodegradation behaviour of Fe-based alloys in Hanks’ Balanced Salt Solutions: Part I. material characterisation and corrosion testing

Research on Fe-based biodegradable alloys for implant applications has increased considerably over the past decade. However, there is limited information on the influence of testing electrolytes on corrosion product formation and general corrosion progress. In this work, the effect of Hanks’ Balanced Salt Solution (HBSS) with or without Ca2+ on the corrosion of Fe, Fe35Mn and (Fe35Mn)5Ag powder-processed coupons has been studied using potentiodynamic polarisation, Electrochemical Impedance Spectroscopy (EIS), and preliminary localised measurement of pH and dissolved oxygen concentration in close proximity to the metal surface. Both Fe35Mn and (Fe35Mn)5Ag alloys showed accelerated corrosion when compared to pure Fe based on potentiodynamic testing results, with FeMnAg exhibiting the highest corrosion rate in Ca2+-containing HBSS. The results indicate that in Ca2+-containing HBSS, the formation of a partially protective Ca/P layer decelerates the corrosion progress, whereas the Fe- and Mn-phosphates formed in Ca2+-free HBSS do not have the same effect. The Ca/P layer on (Fe35Mn)5Ag experienced a reduction in resistance following several hours of testing, indicating partial loss of its protective effect.

Effect of Co/Ni Substituting Fe on Magnetocaloric Properties of Fe-Based Bulk Metallic Glasses

In this work, Fe80-xMxP13C7 (M = Co, Ni; x = 0, 5 and 10 at.%) bulk metallic glasses (BMGs) were prepared, and the effect of the Co/Ni elements substitution for Fe on the magnetocaloric properties of Fe80P13C7 BMG has been investigated systematically. The Curie temperature (TC) of the present Fe-based BMGs increases with the substitution of Fe by Co/Ni. The magnetic entropy change (ΔSM) of the present Fe-based BMGs increases first and then decreases with the increase of Fe substituted by Co, but monotonically decreases with the increase of Fe substituted by Ni. Among the present Fe-based BMGs, the Fe75Co5P13C7 BMG exhibits the maximum ΔSM value of 5.21 J kg−1 K−1 at an applied field of 5 T, which is the largest value among Fe-based amorphous alloys without any rare earth elements reported so far. The present Fe-based BMGs exhibit the large glass forming ability, tunable TC and enhanced ΔSM value, which are beneficial for magnetic refrigerant materials.