Fe-Mn System Research Articles

Forming the structure and the properties of electric arc coatings based on high manganese steel alloyed with titanium and niobium carbides

The formation of the phase composition, structure, and properties of electric-arc coatings by electrode materials based on high-manganese austenite steel, which is strengthened by twinning steel alloyed by titanium and niobium carbides, was studied. Hardfacing alloys were applied using flux-cored arc welding (FCAW), which consisted of a shell of low-carbon steel filled with a powder mixture containing ferrosilicon manganese, graphite, rutile, fluorite, carbide of niobium or titanium.The phase composition of the coatings was calculated by the CALPHAD method using the Thermo-Calc and Dictra software to simulate equilibrium and non-equilibrium alloy cooling, respectively. The results of calculations show that the cooling conditions at hardfacing lead to the formation of the structure of metastable manganese austenite and minor (0.2 % by weight) amount of carbide of cementite type M3C. This amount of the carbide phase cannot adversely affect the ability of austenite to deformation strengthening. Crystallization of titanium and niobium carbides begins at a high temperature of ~2,400 K and does not affect the phase transformations of austenite into the liquid and solid state. Thus, after cooling, the coating structure mainly consists of two phases, specifically, austenite and niobium or titanium carbide MS in an amount of ~9 vol. %.According to the results from studying the microstructure using scanning electron microscopy and energy-dispersive X-ray spectroscopy of the selected area, the MС carbide phase is released as evenly distributed small particles of the shape that is close to cubic. Carbide particles are mainly located inside austenite grains.Measurement of the hardness of hardfacing coatings shows that at alloying high-manganese austenite steel with niobium and titanium carbides, the hardness significantly increases in hardfacing state from 22 to 35 HRC and after cold plastic deformation from 44 to 52 HRC. The research of wear resistance under conditions of wear by the dry sand – rubber roller pattern shows that TiC and NbC additives can significantly (by 1.6–1.8 times) improve wear resistance of hardfacing coatings.Due to the ability to deformation strengthening in combination with high abrasion resistance, the obtained materials for hardfacing the systems Fe–Mn–Nb–Si–C and Fe–Mn–Ti–Si–C can be recommended for application to working surfaces of digging machines

Thermodynamic assessment and experimental investigation of the systems Al–Fe–Mn and Al–Fe–Mn–Ni

The ternary Al–Fe–Mn and the quaternary Al–Fe–Mn–Ni systems were re-assessed/assessed with special emphasis on compositions relevant for Fe-based shape memory alloys (SMAs), to further improve materials properties and to reliably predict phase transformation in these systems. The thermodynamic assessment was based on literature data, as well as experimental investigations regarding the phase equilibria formed between the phases A1, A2, B2 and β-Mn. Key isothermal sections were studied at 725 and 1000 °C in the Al–Fe–Mn system and at 1000 and 1175 °C in the Al–Fe–Mn–Ni system, respectively. For the quaternary Al–Fe–Mn–Ni system, additional diffusion-couple experiments were conducted to investigate target regions of the phase diagram. Calculations based on the present description are in excellent agreement with the data available in literature and the experimental investigations of the present work for both, the Al–Fe–Mn and the Al–Fe–Mn–Ni systems.

Quantitative Determination of Low Contents of Manganese in Steels by EPMA.

The fluorescence effect induced by Kβ photons is usually so small that it can be neglected. However, in the Fe-Mn system, omitting Kβ fluorescence correction will lead to the overestimation of the Mn content especially when Mn is the minor alloy element. In this study, the error in the Mn concentration induced by Kβ fluorescence was investigated by both Monte Carlo simulation, using the pyPENELOPE program, and systematic electron probe measurements on the Fe-0.53% Mn alloy standard by the aid of CalcZAF software. It is shown that the error caused by Kβ fluorescence exceeds 4% for the Fe-0.53% Mn alloy. The problem can be overcome by utilizing CalcZAF in which β-line fluorescence has been included, or by employing a similar standard Fe-0.85% Mn for Mn in the absence of β-line fluorescence correction. In addition, a modified calibration curve method, using k-values instead of X-ray intensity as a variable, is presented and used to measure the Mn concentration. The accuracy of this method is as good as or better than that of the conventional matrix correction method. Compared with conventional calibration curve methods, it is time-saving because the k-value is not sensitive to instrument fluctuations and the established curve remains valid for a long period.

Induced high-temperature ferromagnetism by structural phase transitions in strained antiferromagnetic \u03b3-Fe50Mn50 epitaxial films

Strain effects in epitaxial films can substantially enhance individual functional properties or induce properties which do not exist in corresponding bulk materials. The bcc α-Fe50Mn50 films are a ferromagnetic with a Curie temperature between 650 K and 750 K, which do not exist in nature can be manipulated through the tensile strain. In this study, γ-Fe50Mn50 epitaxial films grown on GaAs(001) using molecular beam epitaxy are found to structural transition from the face-centered-cubic (fcc, a = 0.327 nm) γ-phase to the body-centered-cubic (bcc, a = 0.889 nm) α-phase. For α-Fe50Mn50 epitaxial films, ferromagnetism is accompanied by structural phase transition due to the tensile strain induced by the differences of the thermal expansion between the film and the substrate. Moreover, by realizing in epitaxial films with fcc structure a tensile strain state, phase transitions were introduced Fe-Mn alloy system with bcc structure. These findings are of fundamental importance to understanding the mechanism of phase transition and properties of epitaxial CuAu-I type antiferromagnetic alloy thin films under strain.

Al Deoxidation Equilibrium of Fe-10-30 mass%Mn Melt at 1873 K

Efficient and sophisticated refining process for highly alloyed steel is required in order to meet the highest-priority demand for physical and chemical properties of such steel products. In the present study, Al deoxidation equilibrium of the molten Fe-Mn system for which the demand has been continuously increasing nowadays was measured in the Mn composition range from 10 to 30 mass% at 1873 K. Equilibrated oxide phase varied depending on Al concentration; MnAl2O4 or Al2O3 was equilibrated at relatively low or high concentration range, respectively. The interaction parameter between Al and O, and equilibrium constant of Al2O3 dissolution reaction estimated from results of Al2O3-equilibrated experiments did not show the significant Mn concentration dependence of the Fe-Mn melt.

A thermodynamic assessment of the binary Fe-Mn system for the third generation of Calphad databases

In developing the third generation of Calphad databases, the next step after proper description of the unaries is to assess higher-order systems, i.e. binaries, ternaries etc. A new description of the Fe-Mn system is presented in this work, based on the Calphad approach. New models with a stronger physical basis are used to model the Gibbs energy of the phases. For this purpose, the revised magnetic model is used to fit the magnetic properties versus the most recent experimental and ab-initio data. An acceptable magnetic phase diagram is reproduced, and a reasonable fit for the phase diagram is achieved which will prevent possible artefacts in higher-order systems. The description is valid down to 0 K, which make it very useful as a starting point for modelling phase transformations occurring at low temperatures.

On the question of the applicability of G.V. Samsonov’s activated sintering concept in studying the processes of powder material deformation

Some Yu.G. Dorofeev’s memoirs about joint work and meetings with outstanding materials science expert G.V. Samsonov are given. Meetings in Yugoslavia were of particular importance where G.V. Samsonov and M.M. Ristićtogether with other worldfamous scientists created the International Institute for the Science of Sintering. In the last years of his life, G.V. Samsonov proposed the concept of sintering activation by additives that act as electron acceptors and additionally contribute to the ionic bond in the matrix material. The paper considers the possibility of using this concept in the development of activating additives that reduce the activation energy of the plastic deformation of iron-based powder materials. Sintering activation when forming stable electronic configurations can be accomplished by: 1) accelerating the grain-boundary heterodiffusion of the matrix material in the presence of phase segregations containing an activating microadditive (W–Ni system); 2) intensifying shrinkage durng the plastic flow of matrix material particles facilitated by diffusion porosity formed in the additive particles as a result of predominant additive atom diffusion into base metal particles (Fe–Ni, Fe–Co, Fe–Mn systems); 3) increasing the self-diffusion coefficient of base metal atoms due to the expanded area of a less close-packed crystal lattice (αphase) upon activating additive dissolution (Fe–Mo system). The article reviews the information available on the prospects for using manganese and chromium as compaction activating additives. The compaction activation energy of iron-based powder materials can be reduced by introducing manganese additives. At the same time, the use of diffusion saturation technology is promising. The question of using chromium as an activator does not have an unambiguous answer and suggests the need for further study.

Do Wet-Dry Ratio and Fe-Mn System Affect Oxidation-Reduction Potential Nonlinearly in the Subsurface Wastewater Infiltration Systems?

To understand characteristics of on-line oxidation-reduction potential (ORP) in a subsurface wastewater infiltration system (SWIS) under different intermittent influent conditions, ORP among five matrix depths at wet-dry ratios (Rwds) of 2:1, 1:1 and 1:2 with a hydraulic load of 0.10 m3·(m2·d)−1 were monitored. Results showed that the optimal Rwd for the SWIS was 1:1. In that case, ORP at 40 and 65 cm depths changed significantly, by 529 mV and 261 mV, respectively, from the inflow period to the dry period, which was conducive to the recovery of the oxidation environment. It was concluded that ORP varied nonlinearly in strongly aerobic and hypoxic environment. Wastewater was fed into the SWIS at 80 cm and dissolved oxygen diffused at the initial period of one cycle. As a consequence, ORP at 65 cm increased with water content increasing. However, ORP at 40 and 95 cm displayed inverse trends. Moreover, results showed that ORP decreased with Fe2+ and Mn2+ increasing under aerobic conditions (p < 0.05) because Fe2+ and Mn2+ moved with wastewater flow. Effluent met reuse requirements and no clogging was found in the SWIS during the operation.

Purification of Aluminium Cast Alloy Melts through Precipitation of Fe-Containing Intermetallic Compounds

Aluminium secondary materials are often contaminated by impurities such as iron. As the alloy properties are affected by impurities, it is necessary to refine aluminium melts. The formation of Fe intermetallics in aluminium melts can be used to develop a purification technology based on the removal of intermetallic compounds. In this study, the temperature range for effective separation of intermetallics was determined in an industrial-relevant Al–Si–Fe–Mn system with 6 to 10 Si wt. %, 0.5 to 2.0 Fe wt. %, and 0 to 2.0 Mn wt. %. Based on DTA (Differential Thermal Analysis) and SEM (scanning electron microscope) results and following the rules of phase boundary drawing, isopleths were drawn. This method allows to derive the temperature ranges of intermetallic phase stability and can be applied for the assessment of melt-refining parameters.

Purification of Aluminium Cast Alloy Melts through Precipitation of Fe-Containing Intermetallic Compounds

Aluminium secondary materials are often contaminated by impurities such as iron. As the alloy properties are affected by impurities, it is necessary to refine aluminium melts. The formation of Fe intermetallics in aluminium melts can be used to develop a purification technology based on the removal of intermetallic compounds. In this study, the temperature range for effective separation of intermetallics was determined in an industrial-relevant Al–Si–Fe–Mn system with 6 to 10 Si wt. %, 0.5 to 2.0 Fe wt. %, and 0 to 2.0 Mn wt. %. Based on DTA (Differential Thermal Analysis) and SEM (scanning electron microscope) results and following the rules of phase boundary drawing, isopleths were drawn. This method allows to derive the temperature ranges of intermetallic phase stability and can be applied for the assessment of melt-refining parameters.

Structure and Corrosion-Electrochemical Behavior of Bioresorbable Alloys Based on the Fe–Mn System

The structural state under varied conditions of thermal and thermomechanical treatment, the possibility of realization of a reversible martensitic transformation, and electrochemical behavior and corrosion resistance of iron and its bioresorbable alloys Fe–(23–30)–Mn–5Si in the solution simulating the liquid fraction of bone tissue of the human body have been investigated by means of electron-microprobe X-ray analysis, X-ray diffraction and metallographic analysis, differential scanning calorimetry, chronopotentiometry, potentiodynamic voltammetry, and gravimetry. It has been shown that the manganese content increase from 23 to 30 wt % results in the significant decrease of the temperatures of the start of the direct and the finish of the reverse martensitic transformation and the acceleration of the electrochemical corrosion. A dual role of silicon in formation of corrosion-electrochemical properties of the alloys has been grounded.

Peritectic phase transformation in the Fe–Mn and Fe–C system utilizing simulations with phase-field method

The present investigation focuses on the solidification of peritectic binary alloys in the systems Fe–Mn and Fe–C by utilizing phase-field simulations. Isothermal and directional solidification conditions were simulated with this approach and the following aspects were investigated: the phases evolution during the peritectic transformation close to the peritectic temperature for the Fe–Mn alloys with 9.5 and 11.0wt.%, the kinetics of the γ-phase growth simultaneously into the liquid and into the δ-phase during the peritectic transformation for several alloys under isothermal conditions in the Fe–Mn peritectic plateau, the γ-phase thickness during the peritectic reaction in the Fe–Mn system and, finally, the behavior of the remaining δ-phase amount at the end of solidification for different cooling rates in the Fe–C peritectic alloy. The model approach was checked by comparison with literature data. It was concluded that the present approach is consistent in yielding quantitative results for the interested phase transformation.

Preparation and characterization of Fe-Mn-doped Barium Hexaferrite permanent magnet

Barium Hexaferrite-based permanent magnets (BaFe12O19) was known for its high magnetic anisotropy and suitability in broad applications. Some dopants and atomic substitutions have been utilized to improve its properties for special purposes. In this paper, the Fe-Mn system was used as a dopant for preparing Fe-Mn-doped barium hexaferrite permanent magnet using mechanical alloying method. The physical properties of the samples, such as bulk density, and porosity were examined to study the effect of the dopant. In addition, the crystal structure and magnetic properties of the samples were analyzed using X-Ray Diffractometer (XRD) and Vibrating Sample Magnetometer (VSM), respectively. It is found that the addition of Fe-Mn into barium hexaferrite contributes on the appearance of minor phases such as iron oxide-based magnetite and hematite. In addition, the XRD peak shifted to smaller angle which is likely due to Mn ion substitution and lattice strain within the hexaferrite crystal. It is also observed that the magnetic properties of Fe-Mn-doped barium hexaferrite was inferior to that of the undoped samples. It means that the formation of magnetite and hematite from Fe-Mn dopant during the sintering process is dominant and results to the reduction of hard magnetic properties of the samples.

Electrical control of antiferromagnetic metal up to 15 nm

Manipulation of antiferromagnetic (AFM) spins by electrical means is on great demand to develop the AFM spintronics with low power consumption. Here we report a reversible electrical control of antiferromagnetic moments of FeMn up to 15 nm, using an ionic liquid to exert a substantial electric-field effect. The manipulation is demonstrated by the modulation of exchange spring in [Co/Pt]/FeMn system, where AFM moments in FeMn pin the magnetization rotation of Co/Pt. By carrier injection or extraction, the magnetic anisotropy of the top layer in FeMn is modulated to influence the whole exchange spring and then passes its influence to the [Co/Pt]/FeMn interface, through a distance up to the length of exchange spring that fully screens electric field. Comparing FeMn to IrMn, despite the opposite dependence of exchange bias on gate voltages, the same correlation between carrier density and exchange spring stiffness is demonstrated. Besides the fundamental significance of modulating the spin structures in metallic AFM via all-electrical fashion, the present finding would advance the development of low-power-consumption AFM spintronics.

O79] The isothermal section of the phase diagram of Gd–Fe–Mn system at 773K

O79] The isothermal section of the phase diagram of Gd–Fe–Mn system at 773K

Ordering in ternary BCC alloys applied to the Al–Fe–Mn system

TWIP (TWinning Induced Plasticity) steels are attracting a lot of attention due to their combination of strength and ductility. In a previous work [1] (B. Lindahl, M. Selleby, Calphad 43 (2013) 86–93) a thermodynamic assessment of the Al–Fe–Mn system, which forms the basis of TWIP steels, was presented. The previous assessment treated the A2/B2 order-disorder transformation in the bcc phase using a two-sublattice model. In the present work a four-sublattice model has been used in order to also be able to describe the transition into the ordered D03 compound that occurs at lower temperatures. pair interaction energies for the Fe–Mn system are evaluated which prove crucial to the extrapolations into the Al–Fe–Mn system. Along with this various aspects of modeling chemical ordering using the Calphad approach are discussed. Equations for determining the ternary compound energies from binary pair interactions energies are presented and equations for determining the parameter values from the ordered parameters are derived.

From High‐Entropy Alloys to High‐Entropy Steels

Inspired by high‐entropy alloys, we study the design of steels that are based on high configurational entropy for stabilizing a single‐phase solid solution matrix. The focus is placed on the system Fe–Mn–Al–Si–C but we also present trends in the alloy system Fe–Mn–Al–C. Unlike in conventional high‐entropy alloys, where five or more equiatomically proportioned components are used, we exploit the flat configurational entropy plateau in transition metal mixtures, stabilizing solid solutions also for lean, non–equiatomic compositions. This renders the high‐entropy alloying concept, where none of the elements prevails, into a class of Fe‐based materials which we refer to as high‐entropy steels. A point that has received little attention in high‐entropy alloys is the use of interstitial elements. Here, we address the role of C in face‐centered cubic solid solution phases. High‐entropy steels reveal excellent mechanical properties, namely, very high ductility and toughness; excellent high rate and low‐temperature ductility; high strength of up to 1 GPa; up to 17% reduced mass density; and very high strain hardening. The microstructure stability can be tuned by adjusting the stacking fault energy. This enables to exploit deformation effects such as the TRIP, TWIP, or precipitation determined mechanisms.

Fe–Mn based minerals with remarkable redox characteristics for chemical looping combustion

Searching for naturally occurring minerals/ores which can only be crushed down and sieved before they are used as oxygen carrier materials (OCM) is one of the main quests of the chemical looping combustion (CLC) community. Three cheap iron and manganese based minerals directly taken from the mining industry are investigated in this study. These minerals are Sinai manganese mineral (Egypt), Guizhou iron mineral (China) and Kryvbas iron mineral (Ukraine). Samples are studied with respect to oxygen capacity and redox kinetics by isothermal hydrogen and methane redox cycling experiments (800–1000°C) and are compared to ilmenite as a widely used state-of-the-art reference. As one of the goals of this benchmarking is to spot minerals which are needless of pre-treatment and activation, no thermal treatment on the samples was performed prior to testing. Degradation issues have also been studied and investigated by SEM. Both Sinai manganese mineral and Kryvbas iron mineral perform well in respect to oxygen capacity and redox kinetics. However the post characterisation demonstrates that cation diffusion is much higher for Fe-based systems compared to the Fe–Mn system which shows much less swelling after 200 cycles.

Determination of the deformation mechanism of Fe-Mn alloys

The energy parameters of planar defects are decisive for understanding the deformation mechanisms of metals. The stacking fault energy has been regarded as a key parameter to determine the activation of the deformation mechanisms of the face-centered cubic metals and alloys. However, it is still under a long debate why the stacking fault energy can be treated to be such an exclusive parameter among the general planar fault energies. We have employed molecular dynamics method to examine the effects of Mn alloying on the deformation behavior of austenitic Fe-Mn systems. The energies of stable and unstable states are calculated by sliding the (111) plane and are analyzed in two different schemes, stacking fault energy and energy barriers, which leads to a contradiction between them. We show that a linear relationship can be identified among the energy barriers. This finding is used to identify the activated deformation mechanism. A new parameter is also suggested to characterize the material deformation.

Ni-free, black ceramic pigments based on Co—Cr—Fe—Mn spinels: A reappraisal of crystal structure, colour and technological behaviour

A reappraisal of crystal structure, optical properties and technological behaviour of black spinels in the Co—Cr—Fe—Mn system was carried out to define the best compositions and disclose the role of crystal chemistry in colouring performance and pigment-glaze interactions. Twenty ternary and quaternary spinel formulations were designed using crystallochemical criteria and prepared by simulating the industrial synthesis. Powder samples were characterized through X-ray diffraction (Rietveld), optical, Raman and Mossbauer spectroscopies, and technological testing in several glazes and glassy coatings. Black spinels fall in a relatively narrow field of unit cell and inversion parameters in between “chromites” and “magnetites”. Their cation distribution is governed by Co2+ occupancy of tetrahedrally-coordinated site T and Cr3+ occupancy of octahedrally-coordinated site M, with Mn3+ hosted at M, while Mn2+ and Fe3+ are distributed over both sites. Nevertheless, Raman and Mossbauer spectra indicate a growing disorder in cation partitioning going towards the iron-rich terms. The pigment technological behaviour depends to a large extent on crystal chemistry of spinels, with no effect by grain or crystallite size. The best colouring performance corresponds to recommended compositions able to withstand corrosion and change in crystal chemistry in contact with melted glaze. Three different pathways can give rise to excellent black pigments: (a) strongly disordered spinels having an inversion parameter i∼0.2; (b) moderately disordered spinels, free of Mn3+, with i<0.1; (c) apparently ordered and normal spinels halfway from cobalt chromite and cobalt ferrite. Poor technological performances are due to different conditions leaving room to colour bleaching (low Cr amount), glaze bloating (excess of Mn3+) and limited resistance to corrosion (oversaturation of site M by Cr+Fe with formation of kenotetrahedral spinels or eskolaite—hematite solid solutions).