Fe Mn Research Articles

Effects of Mn on the interface bonding and mechanical properties of TiC reinforced steel matrix composites

The addition of alloying elements to the steel matrix during the preparation process can significantly affect the properties of TiC reinforced steel matrix composites. In this study, the effects of Mn on the electronic structure and crystal structure stability of Fe supercells, along with as well as the stability of the TiC/Fe(Mn) interface, were analyzed through first-principles calculations. Additionally, 8 vol% TiC/Fe–C composites were prepared through the master alloy method. The effects of Mn contents (0, 0.8, 1.2, 1.6, and 2.0 wt%) on the interface mismatch and mechanical properties of the composites were investigated. The results revealed that Mn formed a solid solution and generated a stronger Fe–Mn bond compared with the Fe–Fe bond, and no interface chemical reaction occurred. The addition of a small amount of Mn improved the interface bonding between TiC particles and the steel matrix. The TiC particles were uniformly distributed in the matrix at the grain boundaries, with only a small amount dispersed within the grains. The TiC particles and steel matrix exhibited excellent, continuous, and stable interface bonding. The addition of Mn reduced the interface mismatch between TiC particles and the matrix. As the Mn content increased, the tensile strength and elongation of the composites first increased and then decreased, while the hardness of the composites increased. The addition of 1.2 wt% Mn resulted in an increase in the tensile strength, elongation, and hardness of the composite by 1160 MPa, 7.3%, and 43 HRC, respectively. These values were 109.8%, 151.7%, and 31.1% higher than those of the composite without Mn addition. However, an excess of Mn led to severe distortion of the Fe lattice and clustering at the interface, resulting in the degradation of the mechanical properties in the composites.

Abnormal Grain Growth and Pseudoelasticity of Industrially Processed Fe–Mn–Al–Ni Shape Memory Alloy Joined by Metal Inert Gas Welding

The effect of metal inert gas welding on the microstructure, abnormal grain growth and the pseudoelastic properties of industrially processed Fe–Mn–Al–Ni shape memory alloy sheets were studied. Square-butt welds were manufactured using similar filler material. The influence of alternating mean arc linear energy on the microstructure of the individual zones is shown. A correlation between the process parameters, the associated heat input, the grain morphology and the α/γ-ratio could be deduced. As the mean arc linear energy increases, the α/γ-ratio in the fusion zone and the heat-affected zone increases. To evaluate the influence of the welding process on abnormal grain growth, a post-weld cyclic heat-treatment was carried out. Although no loss of major alloying elements in the fusion zone was observed after welding, metal inert gas welding has a significant effect on grain growth upon cyclic heat treatment. While abnormal grain growth occurred in the base material, a polycrystalline microstructure characterized by significantly smaller grain sizes was visible in the former fusion zone. Incremental strain tests revealed severe plastic deformation near the grain boundaries in the former fusion zone. However, the grain boundaries of the bamboo-like grown grains in the base material turned out to be more critical for structural failure.

Arsenic in a Karstic Paddy Soil with a High Geochemical Background in Guangxi, China: Its Bioavailability and Controlling Factors

Arsenic (As) is of widespread concern, as its elevated contents in soil and water have a serious impact on the ecological environment and human health. Soils in karst regions are characterized by a high geochemical background of As. However, the bioavailability of As in paddy soils and the potential risk of As transfer from the soil to rice remain unclear. In this study, 305 paired soil–rice samples were collected from karst regions in Guangxi, China, in order to examine the controlling variables and As bioavailability in the soil–rice system. According to this study, the karst region’s paddy soil had higher As concentrations than the non-karst region’s paddy soil. The As concentration in the rice grains was low, with only 0.62% of the rice samples exceeding the permissible value of inorganic As (0.2 mg/kg). Arsenic in the karstic paddy soils existed mainly in the residual fraction, while the water-soluble and exchangeable fractions, which are readily absorbed by rice, accounted for a relatively small proportion. The high content but low bioavailability of As in the karstic paddy soil was mostly attributed to the abundant Fe–Mn nodules, which contributed 64.45% of the As content in the soil. Within the Fe–Mn nodules, As was primarily bound to Fe-(oxyhydr)oxides, which could be released into the paddy soil under certain reduction conditions via the reductive dissolution of Fe-(oxyhydr)oxides. Under the natural pH conditions of the karstic paddy soil (pH 4.9–8.38), the leaching of As was almost negligible, and As could be steadily retained within the Fe–Mn nodules. However, extremely acidic or alkaline conditions promoted the release of As from the Fe–Mn nodules.

Tailoring functional properties of a FeMnSi shape memory alloy through thermo-mechanical processing

The influence of thermo-mechanical processing on the microstructure and functional properties of a Fe–17Mn–5Si–10Cr–4Ni-1(V–C) (wt%) shape memory alloy was systematically investigated. The as-received material was subjected to 25 % cold rolling followed by a recrystallization at 925 °C and single or double aging treatments. Transmission electron microscopy revealed the formation of the ε-martensite and annealing twin boundaries and Shoji-Nishiyama orientation relationships of ε-martensite and γ-austenite in double aged specimen. Cyclic tensile testing demonstrated that the recrystallized and double aged alloy exhibited excellent pseudoelasticity. In the incremental strain test, the alloy achieved the highest peak stress and pseudoelasticity at each cycle. In the constant stresses test, the alloy accumulated a minimal residual strain of only 0.12 % over 50 cycles. This stability was attributed to a strong precipitation strengthening and the interactions between the martensite and the refined microstructural features. In addition, the recrystallized and double aged sample resulted in the greatest recovery stress of 450 MPa upon heating after pre-straining, because of its high yield strength suppressing new martensite formation during cooling process. The results of high-resolution transmission electron microscopy identified a non-Shoji-Nishiyama orientation relationship between the stress-induced ε-martensite after the stress recovery test and γ-austenite matrix, inducing additional irrecoverable strain and raising the recovery stress. Overall, the study can demonstrate that the tailored thermo-mechanical processing enables optimizing the functional performance of FeMnSi alloys.

New insight into genesis of the Maojun laterite Fe–Mn deposit in the Lanshan area, Hunan Province, South China: Evidence from detailed mineralogical and geochemical studies

Laterite Fe–Mn deposits are widespread in South China, with the majority of Fe–Mn ore being present in residual quaternary clay beds. However, detailed geological data on the lateritization of low-iron-content carbonate rocks are rare. In this study, we present new results on the mineralogy and geochemistry, as well as a genetic model, of the Maojun laterite Fe–Mn deposit in the Lanshan area, Hunan Province, South China. The profile sequence of laterite consists of an eroded bedrock horizon at its base, an intermediate black–brown clay layer containing earthy Fe–Mn ore, and a reddish-brown clay layer with nodular ferromanganese ore in contact with reddish-brown or yellowish-brown clay on top. Field evidence and chemical analysis indicated that during lateritization, the Mn-Fe-containing carbonate rocks of the Huanggongtang (D2h) and Shetianqiao formations (D3s) saw a more significant removal of mobile elements (Mg, Ca, and Na) whilst insoluble elements (Fe, Mn, Si, Al, Pb, and Zn) exhibited persistent enrichment in situ. Discriminative diagrams of Fe–Mn mineralization, as well as the assemblage-related enrichment of Y, U, Mo, Pb, and Zn and depletion of high-field-strength elements Zr, Nb, and Th, imply that subsequent hydrothermal circulation overprinted on the previously formed hydrogenous deposit. Mineralogical studies conducted using XRD, EPMA, HR-TEM, and TIMA indicated the predominance of iron and manganese oxides; hematite, goethite, limonite, and hollandite were identified as major oxide phases and cryptomelane, pyrolusite, and coronadite were present in minute quantities. Similar minerals constitute the upper ferromanganese nodule horizons, although they possess distinct textures and concentrations. The mineralogy, geochemical associations, and Ti mass balance show a continuous vertical evolution from top to bottom in the lateritic profile. Ferromanganese concretions from the drenching zone with poorly crystallized Al–goethite, Al–hematite, limonite, Fe–kaolinite, Fe–Mn oxides and hollandite predominate in shallow parts, and microcrystalline hematite, goethite and hollandite were found in deeper layers. Mn2+ can be rapidly oxidized and precipitated on the surface of hematite and limonite as high-valence-state (Mn4+) manganese oxides and binds strongly with mobile elements (Ba, K, Pb, Zn, Ca, and Ni). Petrographical, mineralogical, and geochemical studies show that three stages comprised the formation of the Maojun laterite Fe–Mn deposit.

Effect of Plastic Deformation in Various Temperature-Rate Conditions on Structure and Mechanical Properties of Biodegradable Fe–30Mn–5Si Alloy

Effect of Plastic Deformation in Various Temperature-Rate Conditions on Structure and Mechanical Properties of Biodegradable Fe–30Mn–5Si Alloy

Study on the dynamic adsorption and recycling of phosphorus by Fe–Mn oxide/mulberry branch biochar composite adsorbent

In this study, the Fe–Mn oxide/mulberry stem biochar composite adsorbent (FM-MBC) was prepared and fully characterized by SEM-EDS, XRD, BET, and XPS. The solution pH (3.0, 4.5, and 6.0), initial concentration of phosphorus (10, 20, and 30 mg L−1), adsorbent bed height (2, 3, and 4 cm), and solution flow rate (1, 2, and 3 mL min−1) were investigated to analyze the breakthrough curves. The results showed that the breakthrough time was shortened as the initial phosphorus concentration, the flow rate increased and the bed height decreased. Higher initial phosphorus concentrations, flow rates, and lower bed heights, led to a faster breakthrough of phosphate ions in the FM-MBC adsorbent. Additionally, it was observed that increasing the pH value was not conducive to the adsorption of phosphorus by the FM-MBC adsorbent. Dynamic adsorption data were fitted to four models (Yoon-Nelson, Thomas, Adams-Bohart, and Bed Depth Service Time), and the R2 values of the Thomas and Yoon-Nelson models exhibited minimal variation, suggesting that the dynamic adsorption process of FM-MBC was rather intricate. The saturated fixed-bed column (including FM-MBC) was regenerated with NaOH or HCl, and it was found that a 0.1 mol L−1 NaOH solution had the best regeneration effect. XRD analysis showed that the reaction product between the FM-MBC composite and phosphate anions was Fe3(PO4)2·H2O. Moreover, the experimental results that FM-MBC can successfully be used to remove phosphorus from actual wastewater.

Denitrification driven by additional ferrous (Fe2+) and manganous (Mn2+) and removal mechanism of tetracycline and cadmium (Cd2+) by biogenic Fe–Mn oxides

Zoogloea sp. MFQ7 achieved excellent denitrification of 91.71% at ferrous to manganous ratio (Fe/Mn) of 3:7, pH of 6.5, nitrate concentration of 25 mg L−1 and carbon to nitrogen ratio of 1.5. As the Fe/Mn ratio increasd, the efficiency of nitrate removal gradually decreased, indicating that strain MFQ7 had a higher affinity for Mn2+ than Fe2+. In situ generated biogenic Fe–Mn oxides (BFMO) contained many iron-manganese oxides (MnO2, Mn3O4, FeO(OH), Fe2O3, and Fe3O4) as well as reactive functional groups, which play an significant part in tetracycline (TC) and cadmium (Cd2+) adsorption. The adsorption of TC and Cd2+ by BFMO can better fit the pseudo-second-order and Langmuir models. In addition, multiple characterization results of before and after adsorption indicated that the removal mechanism of BFMO on TC and Cd2+ was probably surface complexation adsorption and redox reactions.

The Boumaadine Fe–Mn–Pb–Cu (± Au) ore deposit (Jbel Skindis, eastern High Atlas, Morocco): New insights from geological, hydrothermal alteration and geochemical investigations

Petrographic, structural and geochemical analysis combined with SEM and XRD were performed on the Boumaadine Fe–Mn–Pb–Cu (±Au) mineralization of Jbel Skindis in the eastern High Atlas, (Morocco). The results indicate a polyphasic process of mineralization, which produced orebodies with distinct features and different chemical conditions formation. The earliest mineralization formed replacement and disseminated Fe–Mn–Pb orebodies under oxidizing conditions, with a mineral assemblage composed of coronadite, plumboferrite, cesarolite, specularite and calcite, in association with a large-scale hydrothermal alteration consisting essentially of Fe–Mn minerals, i.e., ferroan dolomite, hematite, jacobsite and limonite. The second event was formed under reducing conditions that generate some veins filled mainly by sulfides (galena, with minor pyrite and chalcopyrite), in addition of calcite and dolomite.The mineralization is hosted in Lower Liassic dolostones and is linked to the structural evolution of the study area. Fractures related to the displacement of the Boumaadine fault seem to control the disposition and the localization of the alteration and the mineralization: (i) the Fe–Mn–Pb oxides are related to a NE-SW conjugate fault system generated during the first phase of deformation, with a horizontal principal stress striking NNW-SSE, and (ii) the sulfide mineralization occurs mainly as filling conjugate fractures of two preferentially directions striking N80–90 and N150-165 with a slight dip (15–40°) to the NE. These latter were caused by a dextral movement along the Boumaadine fault, generated during the late phase of deformation with a NW-SE bearing horizontal principal stress.The deep-seated Boumaadine fault has acted as pathways for the rising fluids, and supports the origin of lead and other metals from the Paleozoic basement. The Triassic evaporitic sequence along the Boumaadine fault has also contributed to the chemical composition of the fluid, and represents the potential source of both the salinity and sulfur. The oxide-sulfide mineralogical assemblage and its associated alteration emphasize a polyphasic hydrothermal activity with distinct physicochemical conditions; an iron-manganese rich, and highly oxidizing brine is considered to be responsible for the Fe–Mn alteration and for the deposit of the oxide assemblage. Furthermore, a mixing of the oxidizing fluid with a meteoric reducing fluid could have resulted in the sulfide-rich ore.

High entropy Fe–Mn–Ni–Co–Al–C alloys from an industrial steel

High entropy alloys (multiprinciple element alloys) were produced by dilution of the base component in a Fe–Mn–Al–C alloy. The studied Fe–Mn–Ni–Al–C and Fe–Mn–Ni–Co–Al–C alloys were treated thermally and mechanically. These alloys were studied by X-ray diffractometry and electron microscopy, while mechanical properties were tested by mechanical loading. A dual-phase cF4 and cP2 structure was formed. The alloys showed high-hardness values and high-strain hardening ability but when hot rolled exhibited precipitation of carbides. These alloys are considered to be model alloys for the development of future high-entropy alloys based on industrial steels.

Effect of Al–Fe–Mn–Si particle characteristics on the growth morphology and corrosion resistance of anodic oxide film on AA 3003 aluminium alloy

This study examines the impact of Al–Fe–Mn–Si particle characteristics in AA3003 alloy on the morphology and resistance of anodic oxide films against corrosion. The results show that low-silicon-content Al–Fe–Mn–Si particles oxidise simultaneously with the matrix to form a discontinuous porous oxide film, and complex small pores are formed in the porous layer; although high-silicon-content Al–Fe–Mn–Si particles have the same oxidation rate as the alloy matrix, the growth of the oxide film is hindered by unoxidised particles in the porous layer due to the influence of particle size and chemical composition, resulting in uneven growth of the oxide film and ultimately causing defects such as enlarged pores and cracks. A mechanism model for Al–Fe–Mn–Si particles affecting the morphology of oxide film growth was established. Electrochemical test results show that compared with the oxide film of the high-silicon-content alloy, the oxide film of the low-silicon-content alloy has better corrosion resistance performance, with a corrosion potential of −0.512V (compared with −0.836V for the high-silicon alloy) and a corrosion current density of 3.34 × 10−8A/cm2 (compared with 9.614 × 10−7 A/cm2 for high-silicon alloy). The barrier layer attained an elevated impedance value and exhibited self-repairing capabilities.

Effects of Fe/Fe–Mn oxides loaded biochar on anaerobic degradation of typical phenolic compounds in coal gasification wastewater: Performance and mechanism

In this study, two kinds of magnetic biochar (BC) were synthesized by loading Fe (FeBC) and Fe–Mn oxides (FMBC) and their effects on anaerobic phenolics degradation were investigated. Compared with BC/FMBC, FeBC addition achieved the superior phenolics biodegradation even for 3,5-xylenol. Compared with control, FeBC addition enhanced CH4 production by 100.1 % with the lag time shortened from 9.5 days to 6.6 days while it increased to 11.2 days with FMBC addition. FeBC addition activated adsorption-biodegradation and Fe (III) reduction with the improved electron transfer activity, adenosine triphosphate and cytochrome C concentrations. Abundant phenol degrading bacteria, electroactive bacteria, syntrophic partners could be enriched by FeBC addition, contributing to the enhanced benzoyl-CoA and methanogenesis pathways. However, this enhancement was inhibited by FMBC addition owing to the accumulation of reactive oxygen species. This study provided novel insights into the application of magnetic BC to enhanced anaerobic treatment of phenolic wastewater.

Influence of dynamic strain aging on low-cycle fatigue behavior in nano-sized κ-carbide strengthened FeMnAlC lightweight steel

The effects of dynamic strain aging (DSA) on the cyclic response and deformation behavior of a hot rolled Fe–22Mn–8Al–0.9C–0.02Nb (wt.%) lightweight steel have been investigated during strain-controlled low-cycle fatigue (LCF) tests at the temperature range of 25–400 °C. The initial microstructure consisted of a complete γ-matrix with nano-sized κ-carbides. During LCF testing, the cyclic stress amplitude displayed a monotonous softening until fracture at 25 °C, 100 °C, and 400 °C in all the investigated strain ranges (Δεt) of 0.8–2.2 %. However, at 200 °C and 300 °C, cyclic softening was followed by pronounced cyclic hardening. Notably, hysteresis loops at the cycle of half-life exhibited serrations in the flow stress at 200 °C and 300 °C. This indicated that cyclic hardening was attributed to the DSA phenomenon, which was confirmed by a negative strain rate sensitivity at 200 °C and 300 °C. A significant reduction in LCF life was observed under the DSA regime. During LCF testing, sequential transmission electron microscopic (TEM) observation indicated that deformation led to the formation of shear bands in multiple directions. Gliding of wavy dislocations was frequently observed at 200 °C compared to that at 25 °C, which resulted from the dragging effect by carbon solute atoms.

Formation behavior of Fe–Zn intermetallic layers at the interface between Fe–Mn and pure Zn melt at 460°C

Formation behavior of Fe–Zn intermetallic layers at the interface between Fe–Mn and pure Zn melt at 460°C

Achieving the selectivity of the oxygen reduction reaction by regulating electron spin states and active centers on Fe–Mn–N6–C dual-atom catalysts

As the first attempt to reveal the intrinsic relationship between electron spins and catalytic selectivity, this work offers new insights into the rational design of efficient transition metal atom-dispersed catalysts through spin regulation.

Formation Behavior of Fe–Zn Intermetallic Layers at the Interface between Fe–Mn and Pure Zn Melt at 460°C

Formation Behavior of Fe–Zn Intermetallic Layers at the Interface between Fe–Mn and Pure Zn Melt at 460°C

Syngas production from phenolic pollutants via a series of hydroxylation, ring cleavage, and aqueous-phase reforming catalyzed by a hydrotalcite-supported Fe–Mn–Ni alloy

A trifunctional catalyst facilitating a series of hydroxylation, oxidative ring opening, and aqueous-phase reforming reactions was developed to convert phenolic wastewater into syngas.

Electrochemical performance of permanganate as an active material for catholyte in aqueous alkaline flow batteries

Fe–Mn flow batteries using Fe(BIS–TRIS) and MnO4-based electrolytes improve voltage and energy efficiencies, proving MnO4 as an effective alternative to ferrocyanide.

Investigation of the interface precipitation on α-Al(Fe,Mn)Si particles in Al–Fe–Mn–Si–Mg–Cu alloy

The effects of particles on precipitation reactions in aluminum alloy have been widely unknown. Al–Fe–Mn–Si–Mg–Cu alloy strengthened with uniformly distributed Al(Fe,Mn)Si nanoparticles was successfully produced in this study. The alloy was then characterised using high-resolution scanning transmission electron microscopy (HRTEM), to provide a fundamental insight into the interface precipitation. Interfacial precipitations of several tens of nanometers in size was formed after aging, which were found to be Al5Cu6Mg2 and Si phases. The results demonstrated that the facetted α-Al(Fe,Mn)Si particles had a significant influence on precipitation adjacent to the α-Al(Fe,Mn)Si/Al interfaces. Semi-coherent α-Al(Fe,Mn)Si/Al interfaces were revealed to have periodically spaced misfit dislocations that are generally considered to be beneficial to heterogeneous precipitation. They not only reduce nucleation energy barriers but also act as short-circuit diffusion paths to accelerate growth rates by transporting solute atoms and vacancies.

Geochemical insights into secular changes in the depositional environment of ferromanganese nodules in the western North Pacific

Understanding Earth's surface dynamics and biological evolution requires deciphering past marine environmental changes. Hydrogenetic ferromanganese nodules formed by the direct precipitation of Fe–Mn oxide/hydroxide from seawater could record the marine environment at the time of deposition, as in the case of ferromanganese crusts. In this study, petrological and geochemical analyses were conducted on ferromanganese nodules collected from the Japanese Exclusive Economic Zone around Minamitorishima Island in the western North Pacific Ocean. Additionally, the results were compared with those of ferromanganese crusts distributed in the same area to elucidate the secular changes in the depositional environment. The mineralogical features (consisting solely of Fe-vernadite with an absence of 10 Å Mn oxide) and the geochemical characteristics (including positive Ce-anomaly and negative Y-anomaly in rare-earth element patterns, high Co contents, and low Cu and Ni contents) of the nodules suggest that the studied nodules are of a hydrogenetic origin. From the inside to the outside of the nodule, the Mn/Fe and Y/Ho ratios decrease while the Th/U ratio increases, indicating a changing depositional environment over time. A similar trend was observed in ferromanganese crusts from the nearby Takuyo-Daigo Seamount. Furthermore, similar compositional changes were observed on the surfaces of the crust samples (uppermost 1–3 mm), which correlated with depth-related changes in seawater oxygen concentrations. Therefore, the observed cross-sectional changes in the chemical compositions of the nodules and crusts may reflect changes in seawater-dissolved oxygen concentrations over time. The Mn/Fe and Y/Ho trends indicate a shift towards a less oxic environment with increasing age while maintaining the current depth profile, implying an expansion of the oxygen minimum zone (OMZ). Moreover, the observed Ni and Cu enrichment, together with the changes in the Mn/Fe and Y/Ho ratios, suggest that the expansion of the OMZ was caused by increased surface ocean productivity.