Fe-Mn Alloys Research Articles

Heterogeneous nucleation of α-Al on naturally formed MgAl2O4 particles during solidification of Al–Mg–Si–Fe–Mn alloys

The nature of the native MgAl2O4 particles found in an Al-5Mg-2Si-0.7Mn-1.1Fe alloy was investigated with scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). An orientation relationship (OR) was identified to be: 8.5° (-1 1 -1)[-1 1 0]α-Al//(2 -2 2)[-1 1 0]MgAl2O4. Different from the OR between the α-Al and the MgAl2O4 particles with a “clean” surface [1], a tilt angle (8.5°) was observed. The atomic templating layer during the nucleation process of α-Al on MgAl2O4 was investigated by considering the interfacial segregation. The contribution of native MgAl2O4 particles to the grain refinement was investigated.

Strategies to increase austenite FCC relative phase stability in High-Mn steels

Several strategies to increase the FCC austenite stability compared to BCC and HCP martensites have been tested and are discussed. The relative stability of the different phases was analyzed by studying the effects of: a) grain size, b) antiferromagnetic ordering of the austenite, c) thermal cycling through the FCC-HCP transition, d) plastic deformation of the austenite and e) combined effects. As a first step, the effect of decreasing the grain size was analyzed in Fe–Mn alloys for Mn contents smaller than 18 wt.%, where BCC and HCP martensites compete in stability. Formation of the BCC phase is inhibited for 15 wt.% and 17 wt.% of Mn for grain sizes smaller than 2 μm. This enabled, for the first time at these compositions, the measurement of the Néel temperature of the austenite using specific heat and magnetic measurements. A comparison of the obtained transition temperatures with accepted models is discussed. The effect of modifying the grain size on the FCC-HCP transition temperatures was also analyzed for 15 wt.% and 17 wt.% Mn contents showing a complete HCP inhibition for grain sizes smaller than 200 nm. A nucleation model for the HCP martensite is considered which includes an additional resistance to the transformation term depending on the austenitic grain size. Additional combined effects on the FCC stabilization are discussed like the interaction between the antiferromagnetic ordering and the introduction of defects by thermal cycling through the martensitic transformation. The analysis can be easily applied to systems with a larger number of components. Results obtained in the Fe–Mn–Cr system are also presented.

Numerical model of selective external oxidation of Fe-Mn binary alloys during non-isothermal annealing treatment

A numerical model has been developed to describe the kinetics of selective external oxidation of Fe-Mn alloys during non-isothermal annealing. This model involves a thermodynamic analysis of possible reactions during annealing and then numerically solves the theoretical equations describing reactive diffusion and heterogeneous nucleation and growth of MnO oxides. The results of the model are the temperature-dependent evolution of the nucleation rate of MnO embryos and the size and surface coverage fraction of MnO particles. The results were validated by experimental data. The study concludes with a parametric analysis of the different physical constants of the model.

Microstructure, mechanical properties, degradation behavior, and biocompatibility of porous Fe-Mn alloys fabricated by sponge impregnation and sintering techniques

In this study, porous iron (Fe)–manganese (Mn) alloys with high porosity were successfully prepared by sponge impregnation and sintering (SIS). The compositions of the porous Fe–Mn alloys were strongly dependent on the sintering temperature, and the Mn content was ~44, 30, and 12 wt.% for alloys sintered at 1100, 1150, and 1200 °C, respectively. The porous Fe–Mn alloys exhibited a well-interconnected porous structure with ~85% porosity and average pore size ranging from 375 to 500 um. The porous Fe-44Mn and Fe-30Mn alloys were mainly composed of a γ-austenite phase, while the porous Fe-12Mn was composed of an α-ferrite phase. The yield strength and elastic modulus of the porous Fe–Mn alloys ranged from 6 to 10 MPa and from 0.12 to 0.37 GPa, respectively, similar to those of cancellous bone. The degradation rate of the porous Fe–Mn alloys decreased over time during immersion in simulated body fluid (SBF), and was 1.0 mm/year for Fe-44Mn, 0.81 mm/year for Fe-30Mn, 0.41 mm/year for Fe-12Mn, and 0.33 mm/year for pure Fe after 14 d SBF immersion. Moreover, the porous Fe–Mn alloys exhibited good biocompatibility with clearly enhanced cell proliferation after direct culturing of osteoblastic MC3T3-E1 cells for 7 d. Thus, these porous Fe–Mn alloys can be anticipated to be promising biodegradable implant materials. Statement of SignificanceThis work reports on porous Fe-Mn alloys with high porosity, suitable mechanical properties and degradation rate, and good biocompatibility. The porous alloys prepared by sponge impregnation and sintering exhibited a well-interconnected porous structure with ~85% porosity and average pore size ranging from 375 to 500 um. The yield strength and elastic modulus of the porous alloys ranged from 6 to 10 MPa and from 0.12 to 0.37 GPa, respectively, similar to those of cancellous bone. The degradation rates in simulated body fluid (SBF) were ~1.0 mm/year for Fe-44Mn, 0.81 mm/year for Fe-30Mn, and 0.41 mm/year for Fe-12Mn, respectively. Moreover, the porous Fe-Mn alloys exhibited good biocompatibility with enhanced cell proliferation after direct culturing of osteoblastic MC3T3-E1 cells

First-Principles Study on Stacking Fault Energy of γ-Fe–Mn Alloys

The ground state properties and generalized stacking fault energy (GSFE) of γ-Fe–Mn alloys with different Mn concentrations are calculated by ab initio simulation. The calculation results of intrinsic stacking fault energies (ISFE) show that Mn atoms have a significant short-range effect on the ISFE; the parabolic relationship between ISFE and Mn atom concentration of antiferromagnetic (AFM) Fe–Mn alloys is explained by the cohesive energy and density of states (DOS) of the alloys. AFM increases ISFE of γ-Fe–Mn alloys compared to non-magnetic (NM). The importance of considering magnetic interactions in ISFE of γ-Fe–Mn alloys is proven and it is very significant to study the deformation behavior of medium manganese steel. We have investigated the stacking fault energy of antiferromagnetic γ-Fe–Mn alloys and proved that that magnetism has an important influence on stacking fault energy in γ-Fe–Mn alloys. We have confirmed the parabolic relationship between ISFE and Mn atom concentration of AFM-Fe–Mn alloys can be explained by the cohesive energy and DOS of the alloys.

Tribological Performance of Porous Ti-Nb-Ta-Fe-Mn Alloy in Dry Condition.

The tribological properties of a novel porous Ti–Nb–Ta–Fe–Mn alloy with 0%, 30%, and 60% porosity were evaluated for biomedical applications. The tribotesting was performed using a ball-on-disc under dry conditions, using an alumina ball and 1 N of a load. The coefficient of friction at the early stage of the porous samples was lower than that of the bulk, 0.2 and 0.7, respectively, but the samples with 30% porosity shift toward the bulk value after a variable number of cycles, while the samples with 60% remained stable after 100,000 cycles. The wear rate of the specimen with 60% porosity was twice as low as that of the bulk. The results are explained by shift in wear mechanism associated with the modified bearing ratio of the porous surface and by the accumulation of wear debris inside the pores, which prevented the development of three-body abrasion.

Deformation-induced martensitic transformation and strain hardening in a nanocrystalline FeMn alloy processed by severe austenite pre-deformation

The FeMn alloy is processed by the surface mechanical rolling treatment when being heated beyond 200 °C for an austenitic state. The nanocrystalline microstructure mainly consisting of austenite phase is resulted in by the severe austenite pre-deformation, which is attributed to the significant mechanical stabilization. This is in contrast with the coarse-grained counterpart that is dominated by epsilon-martensite. The nanocrystalline microstructure in the graded specimen can undergo a large tensile deformation. Martensitic transformation occurs during mechanical loading, and strain hardening of the nanocrystalline microstructure is achieved. Microscopic observations show the growth of epsilon-martensite plates, indicating the multiplication of stacking faults in the nanograins. This study demonstrates a novel approach combining alloy design and plastic processing to produce nanocrystalline materials with strain hardening capacity.

Effects of TiC Addition on Strain-Induced Martensite Transformation and Mechanical Properties of Nanocrystalline Fe-Mn Alloy Fabricated by Spark Plasma Sintering

Effects of TiC Addition on Strain-Induced Martensite Transformation and Mechanical Properties of Nanocrystalline Fe-Mn Alloy Fabricated by Spark Plasma Sintering

Martensitic transformations in Fe-Mn alloy with low stacking fault energy

Object of investigation is highly alloyed binary Fe-Mn alloys which in austenitic state are characterized with different stacking fault energy (SFE). Experimental results using the internal friction and X-Ray methods are obtained for the martensitic non isothermal transformation upon cooling and heating. It was determined that mainly the structural characteristics of the alloys define the type of the possible transformation mechanisms and the products of the martensitic reaction. The role of the SFE for the mechanisms of formation and growth of the martensite phase and the relation between the micro-structural parameters of the solid solution and the mechanism of non isothermal martensitic transformations is shown. On the basis of the existing models of dynamic relaxation associated with phase transformations, here are pivotal conclusions about the characteristics of the non-diffusion mechanism of transformation into a low SFE.

Addressing the slow corrosion rate of biodegradable Fe-Mn: Current approaches and future trends

The movement towards the commercialization of biodegradable Fe has been hampered by the perceived slow degradation rate of the metal in physiological environments. The introduction of Fe-Mn alloys offers promise due to its significantly improved biocorrosion rates, excellent biocompatibility, and non-magnetic properties. However, the issue of slow corrosion rates persists in this alloy and its future hinges on addressing this issue. This short review report presents the current approaches to address this problem, the challenges concerning Fe-Mn corrosion, and some future techniques that may improve the degradation rate of Fe-Mn alloys.

Effect of Mn Modification on the Corrosion Susceptibility of Mg–Mn Alloys by Magnesium Scrap

The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study. The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quantity increases with the Mn addition. Although the presence of Mn-containing Fe-rich particles with unique symbiotic structure can effectively weaken the micro-galvanic corrosion, the presence of more free Fe (Fe-rich particles) does not necessarily lead to severe corrosion of the alloy. The corrosion susceptibility of Mg–Mn–Fe alloy primarily depends on the solubility of iron in the Mg matrix, while it can be significantly reduced by suitable Mn addition. Besides, the tolerance limit of the Fe impurity can be expressed as Femax = 0.0083 Mn (relative to the iron solubility). Only when the Fe/Mn ratio is below 0.0083 can the alloy have excellent corrosion resistance, with the corrosion rate changing in the scope of 0.38 ± 0.09 to 0.54 ± 0.15 mg/cm2 day and icorr from 3 to 9 × 10–4 A/cm2.

Study on aging strengthening and nano precipitates of Cu–Ni–Mn–Fe alloy

This paper presents a systematic study of the precipitation strengthening mechanism in polybasic Cu–Ni–Mn–Fe alloy. The effect of aging treatment on the microstructure, morphologies and phase transition of the Cu–Ni–Mn–Fe alloy were analyzed and discussed using scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and differential scanning calorimeter (DSC), respectively. The θ-MnNi precipitates with a size of 50–100 nm, mainly formed during aging, were considered as the source of the aging strengthening. In addition, there is a semi-coherent between the plane (111) of the θ-MnNi precipitates and the plane (200) of the α-Cu matrix. The density of θ-MnNi precipitates increases with the increase of the aging time. The hardness, yield strength and ultimate tensile strength of the aged alloy increase from 127 to 366HB, 217 to 788 MPa, and 433 to 842 MPa, respectively, which is attributed to precipitation strengthening.

Mind your assays: Misleading cytotoxicity with the WST-1 assay in the presence of manganese.

The WST-1 assay is the most common test to assess the in vitro cytotoxicity of chemicals. Tetrazolium-based assays can, however, be affected by the interference of tested chemicals, including carbon nanotubes or Mg particles. Here, we report a new interference of Mn materials with the WST-1 assay. Endothelial cells exposed to Mn particles (Mn alone or Fe-Mn alloy from 50 to 1600 μg/ml) were severely damaged according to the WST-1 assay, but not the ATP content assay. Subsequent experiments revealed that Mn particles interfere with the reduction of the tetrazolium salt to formazan. Therefore, the WST-1 assay is not suitable to evaluate the in vitro cytotoxicity of Mn-containing materials, and luminescence-based assays such as CellTiter-Glo® appear more appropriate.

New Universality Class Associated with Jahn–Teller Distortion and Double Exchange

The scaling of the magnetic heat capacity in the two manganites La0.85Ag0.15MnO3 and Sm0.55Sr0.45MnO has given the critical exponents α = –0.23 and ν = 0.7433 of the heat capacity and correlation radius of the magnetic order parameter, respectively, which do not belong to any known universality class. These results cannot be attributed to chemical inhomogeneities and/or structural imperfections because the samples are of a high quality. Thus, unusual critical exponents can be associated not only with the chemical disorder and/or structural defects but also with the collective behavior of the lattice. An analogy has been revealed between the effects of the magnetic field and doping on ternary oxides of transition metals: the magnetic field affecting lattice distortions through the orientation of t2g orbitals acts as chemical doping. It seems that scaling relations are more stable than critical exponents in them. The synchronism of lattice distortions and ferromagnetism leads to a novel criticality, but their desynchronization induced by magnetostructural disorder results in the violation of scaling relations between isothermal and isomagnetic exponents. Although double-exchange systems demonstrate novel criticality, they satisfy scaling relations until the magnetic behavior is synchronized with the coherent lattice behavior in the form of cooperative Jahn–Teller distortions. Breaking of double exchange bonds leads to the formation of metamagnetic clusters with magnetic dipole–dipole interaction between them, which desynchronizes lattice distortions and ferromagnetism, resulting in the violation of scaling relations. The proposed new universality class includes diverse materials such as manganites, cobaltites, crystalline Fe–Pt and amorphous Fe–Mn alloys, and high-Tc superconductors. Unusual criticality in double-exchange systems is due to an unusual semiclassical nature of double-exchange ferromagnetism caused by real exchange, i.e., electron current through Mn3+–O–Mn4+ chains with the conservation of the spin rather than by virtual exchange as in a usual ferromagnet. Double-exchange ferromagnetism arises only because to freely itinerate, electrons orient the magnetic moments of Mn cations in a single direction.

In Vitro Degradation, Hemocompatibility, and Cytocompatibility of Nanostructured Absorbable Fe-Mn-Ag Alloys for Biomedical Application.

The addition of noble elements such as Ag was shown as a successful method to accelerate the corrosion rate of absorbable Fe-based alloys. One major concern of Ag addition is its effect on hemocompatibility and biocompatibility. In this study, in vitro degradation and surface analysis of Fe-30Mn-xAg (x = 0, 1, and 3 wt %) alloys as well as their effects on hemocompatibility and cell viability of human umbilical vein endothelial cells (HUVECs) were investigated. The static degradation rate of the alloys was 4.97, 4.69, and 4.49 mg/cm2 for Fe-30Mn, Fe-30Mn-1Ag, and Fe-30Mn-3Ag, respectively. The surface analysis after degradation showed that γ-FeOOH was formed on Fe-30Mn-3Ag, while α-FeOOH was more dominant on Fe-30Mn and Fe-30Mn-1Ag. As γ-FeOOH is more soluble than α-FeOOH, it assists further degradation of Fe-30Mn-3Ag alloy. The high amount of Ag, which induced the hemolysis ratio, however, inhibited coagulation by decreasing the platelet adhesion. Fe-30Mn-1Ag and Fe-30Mn-3Ag alloys show an improved cell viability as compared to that of Fe-Mn alloy. Shear yield strength and shear elastic modulus of the samples after immersion tests were increased, while the ultimate shear strength was not affected. On the basis of the acceptable hemolysis rate, low platelet adhesion, acceptable cell viability, and appropriate mechanical properties after degradation, Fe-30Mn-1Ag can be considered as a suitable blood-contacting Fe-based absorbable alloy.

Mechanical and corrosion properties of iron-mangan materials sintered in the presence of plasma

Abstract The current trend in development of new metallic materials for certain types of implants is turning away from permanent, biologically inert materials to the use of biodegradable materials. Fe–Mn alloys represent high perspective material for development of new generation of temporary and biodegradable implants. The aim of this work was to study mechanical and corrosion characteristics of powder samples containing 25, 30 and 35 wt % of Mn which are fabricated by pressing, sintering, and additional spark plasma sintering. The influence of preparation method (pressing and sintering) to microstructure, phased composition and corrosion behavior of prepared alloys was studied.

Anomalous effect of Si additions upon the paramagnetic-to-antiferromagnetic transition entropy in fcc high-Mn steels

Fe–Mn based alloys with more 12% at. of Mn are usually called High-Mn steels. Several technological properties of High-Mn steels are explained by the presence of the fcc-hcp martensitic transformation. This transition is strongly affected by the para-to-antiferromagnetic ordering transition present in the fcc structure. The magnetic ordering temperature depends on the alloy chemical composition, and strongly stabilizes the fcc austenitic phase, leading to a decrease of the structural transformation temperatures. In several cases, this effect is strong enough to inhibit the martensitic transformation. In the present study, the effect on the magnetic transition of adding Si to high-Mn Fe–Mn alloys is analyzed. Calorimetric measurements are performed in order to obtain the entropy change associated to the magnetic ordering transition. The results are discussed in the light of the available information in the literature. Striking effects are reported, which indicate that Si addition strongly affects the driving force of the martensitic transition.

Effect of Cold Rolling on Stability of HCP and FCC Phases in Fe–Mn Alloys

Effect of Cold Rolling on Stability of HCP and FCC Phases in Fe–Mn Alloys

Theoretical modeling of interstitial carbon impurities in paramagnetic Fe-Mn alloys

We present a generalization of a model that takes into account the magnetic disorder of paramagnetic host with interstitial point defects towards the case of alloy hosts. In the framework of disordered local moment approach combined with magnetic sampling method, we calculate solution enthalpy of carbon impurity in the paramagnetic fcc Fe-Mn steels. First, we use the magnetic special quasirandom structure (M-SQS) method for simulation of the paramagnetic state in Fe-Mn alloys without impurity. Here, Fe and Mn atoms are randomly distributed at the sites of a supercell following the chemical SQS method. Next, to calculate the energies for various magnetic realizations around the interstitial carbon impurity, we vary the position of the impurity within the SQS. Our calculations show that in alloys containing $\ensuremath{\sim}20$ at. % Mn, the solution enthalpy of carbon reduces compared to the pure fcc-Fe. By analyzing the local and global effects of impurity on the properties of the matrix, we discuss various factors that could increase the carbon solubility in high-manganese austenitic steels.

Enhanced mechanical properties of Al–Si–Cu–Mn–Fe alloys at elevated temperatures through grain refinement and dispersoid strengthening

The effect of Ti content on the microstructure and mechanical properties of heat-treated Al–Si–Cu–Mn–Fe alloys was investigated. It was found that the mechanical properties increased with the increase of Ti content. This was attributed to the refinement of grain size, the increased amount of T (Al20Cu2Mn3), the α-Fe (Al15(FeMn)3(CuSi)2) precipitated particles, and the decrease in Al2Cu. At an elevated temperature of 300°C, the heat-treated Al–Si–Cu–Mn–Fe alloy with 0.5% Ti demonstrated the best mechanical properties, which are superior to those of commercial aluminium alloys. The yield strength contribution at 300°C was quantitatively evaluated based on the dispersoid, solid solution, and matrix contributions. It was confirmed that the main strengthening mechanism in the experimental alloys was the dispersoid strengthening.