Partitioning Of Mn Research Articles

Rapid Elemental Partitioning in Medium Mn Steel During Short Time Annealing: An In-Situ Study Using Synchrotron X-Rays

High energy synchrotron radiation was used to perform an in-situ diffraction experiment in medium Mn Fe-6Mn-0.5C-1Al alloy to study the elemental partitiong and austenite phase evolution at different heating, holding and cooling stages. It has been observed that austenite phase fraction increases at inter-critical annealing temperature significantly and it remains stable at room temperature. Austenite phase stability at room temperature is due to rapid partitioning of Mn and C during annealing. The relative change in d-spacing (Δd/d) during heating-cooling indicates partitioning of alloying elements during inter-critical annealing.

Enhancing austenite stability in a new medium-Mn steel by combining deep cryogenic treatment and intercritical annealing: An experimental and theoretical study

We have systematically investigated the effect of deep cryogenic treatment (DCT) and intercritical annealing (IA) on the microstructural evolution and mechanical properties of a hot rolled medium-manganese transformation-induced plasticity (TRIP) steel. By intercritical annealing of DCT-treated steel in the fully martensitic state, ultra-fine-grained (UFG) austenite with different morphologies, namely lath-like and granular, was obtained. It is interesting that carbon segregation caused by DCT promoted the formation of carbide which can be additional nucleation sites for austenite besides the boundary of lath-martensite during austenite revision treatment (ART). Furthermore, the process of austenite growth was simulated by DICTRA and it revealed that austenite nucleated at the boundary of lath-martensite and carbide, and then grew into different morphologies, i.e. lath-like and globular, respectively. Moreover, the dissolution of cementite and finite diffusion distance of Mn limited austenite growth and partitioning of Mn, which resulted in refined grain size and high degree of Mn-enrichment. Consequently, enhanced mechanical-stability of austenite was obtained by DCT+IA, which ensured outstanding combination of mechanical properties, i.e. yield strength of 807 MPa, tensile strength of 1650 MPa and total elongation of 25.3%. The improved strength and ductility was attributed to stabilized austenite that enabled the moderate evolution of TRIP-related work hardening.

The effect of melt composition and oxygen fugacity on manganese partitioning between apatite and silicate melt

Oxygen fugacity and melt composition are both known to have a strong influence on the partitioning of trace elements between coexisting minerals and melt. Previous work has suggested that Mn partitioning between apatite and silicate melt may be strongly affected by oxygen fugacity and could, therefore, act as an oxybarometer. Here, we present a new study on the partitioning of Mn between apatite and melt at high temperature (1400–1250 °C) and 1 GPa pressure, for various melt compositions and oxygen fugacities (NNO +4.7 to NNO -10). We find that there is no demonstrable variation in the partition coefficient for Mn between apatite and silicate melt (DMnAp-m) across the range of fO2 conditions studied here. Instead, we find that DMnAp-m varies significantly with melt composition and that in particular, the proportion of non-bridging oxygens strongly influences partitioning of Mn between apatite and melt. We propose that variations in the Mn content of natural apatite, previously thought to reflect variations in fO2, are instead related to the degree of melt polymerisation. These findings are consistent with the results of Mn K-edge XANES spectroscopy, which demonstrate that Mn in coexisting apatite and silicate glass is present predominantly as Mn2+ regardless of fO2. Furthermore, XANES spectra from a series of silicate glasses synthesised at various oxygen fugacities demonstrate that Mn2+ is the predominant species, and that the average Mn oxidation state does not vary over a wide range of fO2-T conditions.

Effect of chlorine, sulfur, moisture and ash content on the partitioning of As, Cr, Cu, Mn, Ni and Pb during bituminous coal and pickling sludge co-combustion

The effect of chlorine, sulfur, moisture and ash content in blended fuels on the partitioning of As, Cr, Cu, Mn, Ni and Pb during bituminous coal and pickling sludge co-combustion were studied in a horizontal tube furnace. Additives including NaCl, FeS2, water and kaolin were used to simulate coal with high chlorine, sulfur, moisture and ash content, respectively. The percentage of pickling sludge used in all conditions was 10%, and the additives added range was 1%–20%. The experimental results indicated that with increasing NaCl addition the percentage of As, Cu and Pb in bottom ash decreased significantly and the Mn percentage in fly ash increased slightly. Under FeS2 addition condition, Cu and Pb percentage in bottom ash increased significantly due to the incomplete decomposition of the generated CuFe2O4 and PbSO4 while the volatilization of As was promoted. With the increasing addition of water, a higher percentage of As moved into the fly ash from bottom ash, while the proportion of Pb in the fly ash decreased obviously. Under kaolin addition, the As partitioning showed a fluctuation trend, while for Pb and Cu the adsorption was the main effect and their distribution in bottom ash increased. Under all conditions, Cr and Ni partitioning were not affected by additives due to the non-volatility and stability of Cr, Ni and their compounds. Bottom ash XRD analysis results showed that CaF2 disappeared under NaCl addition condition and lots of Ca2Al2SiO7 generated. In addition, FeS2 addition caused more CaSO4 generated due to the sulfation reaction, while no obvious change of bottom ash composition was found under neither water nor kaolin addition.

Alloying-element interactions with austenite/martensite interface during quenching and partitioning of a model Fe-C-Mn-Si alloy

The alloying elements partitioning from martensite to austenite during quenching and partitioning was analysed by coupling in situ High Energy X-Ray Diffraction experiments and 3D atom probe tomography. A rapid and significant carbon partitioning from martensite to austenite without any partitioning of both Mn and Si was highlighted while the interface was immobile. After a relatively short time at 400 °C, a clear Mn partitioning occurs at the vicinity of the α′/γ interface. The analysis conducted indicates that manganese equilibrates its chemical potential during partitioning and raises the issue of the Constrained Carbon Equilibrium model applicability throughout the partitioning process.

In Situ 3D Neutron Depolarization Study of the Transformation Kinetics and Grain Size Evolution During Cyclic Partial Austenite-Ferrite Phase Transformations in Fe-C-Mn Steels

We have analyzed the evolution of the ferrite fraction and average ferrite grain size during partial cyclic austenite-to-ferrite and ferrite-to-austenite phase transformations in an Fe-0.25C-2.1Mn (wt pct) steel using three-dimensional neutron depolarization (3DND). In the 3DND experiments, the ferrite fraction is derived from the rotation angle of the neutron polarization vector, and the average grain size is determined from the shortening of the polarization vector. From these, the number density of ferrite grains is derived, which indicates that grain nucleation is negligible during partial cycling in the intercritical regime and that all transformation kinetics can be attributed to growth processes only. In the multiple successive cyclic partial transformations, the interfacial migration rate was found to be sluggish due to Mn partitioning. The transformation kinetics determined with 3DND was compared to the predicted behaviors for diffusion-controlled simulations under local equilibrium and para-equilibrium interfacial conditions. It was found that the simulation predictions under local equilibrium only qualitatively capture the transformation kinetic with a difference of one order of magnitude in the variation in the ferrite fraction during cycling. The cyclic behavior of this Fe-0.25C-2.1Mn (wt pct) steel shows that the austenite-ferrite interface indeed migrates back and forth during cycling, while at the same time, there is a gradual increase in both the ferrite fraction and the average ferrite grain size over subsequent cycles. The intrinsic cyclic behavior is only visible after subtracting the effect of the progressive interfacial migration into austenite. The present study demonstrates the advantage of 3DND in studying partial cyclic phase transformations over conventional experimental approaches.

On the Spheroidizing Annealing Behavior in Cr/Nb Microalloyed Medium Carbon Steels

The industrial process for the production of fine‐blanking steels, which includes hot‐rolling, cold‐rolling, and spheroidizing annealing, is simulated at a laboratory scale using two medium carbon steels, respectively, microalloyed with Cr and Nb. Two types of hot‐rolled microstructures, that is, “ferrite + pearlite” and bainite are obtained by varying the interrupted cooling temperature (ICT). The microstructure and property evolution during spheroidizing annealing are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron back scattered diffraction (EBSD), and micro‐hardness tester. In Cr microalloyed steel, the dual partitioning of Cr and Mn and slowed growth kinetics of cementite particle are correlated to explain the suppression of ferrite recrystallization. Contrarily, a fast spheroidizing annealing behavior, which led to uniform distribution of cementite particle and fully recrystallized ferritic matrix, is observed in Nb microalloyed steel especially from the hot‐rolled bainite microstructure.

Nanoscale Solute Partitioning and Carbide Precipitation in a Multiphase TRIP Steel Analyzed by Atom Probe Tomography

Nanoscale solute partitioning across multiple constituent phases in a 980-grade quenched and partitioned (Q&P) steel was analyzed using atom probe tomography (APT). The Q&P process was used to increase the C content in the retained austenite phase thereby improving its stability under plastic straining. Significant carbon enrichment of austenite was measured with decreased levels of C in martensite and almost depleted C content in ferrite, supporting the C partitioning mechanism in the literature. The APT analysis of retained austenite surrounded by martensite demonstrated a higher amount of C content compared with retained austenite surrounded by the ferrite phase. Lath and discrete carbide particle precipitation was also observed inside martensite colonies, tying up C and reducing the total amount of C available for austenite stabilization. In addition, the partitioning of Mn and other minor elements was quantitatively investigated by correlating APT and SEM-EBSD. These techniques provide a robust methodology for analyzing nanoscale compositional partitioning in multiphase steels, TRIP steels in particular, which can be used to better explain their microstructure-mechanical property relationships.

Multiscale Characterization of Microstructure in Near-Surface Regions of a 16MnCr5 Gear Wheel After Cyclic Loading

The dependence of the microstructure on the degree of deformation in near-surface regions of a 16MnCr5 gear wheel after 2.1 × 106 loading cycles has been investigated by x-ray diffraction analysis, transmission electron microscopy, and atom probe tomography. Retained austenite and large martensite plates, along with elongated lamella-like cementite, were present in a less deformed region. Comparatively, the heavily deformed region consisted of a nanocrystalline structure with carbon segregation up to 2 at.% at grain boundaries. Spheroid-shaped cementite, formed at the grain boundaries and triple junctions of the nanosized grains, was enriched with Cr and Mn but depleted with Si. Such partitioning of Cr, Mn, and Si was not observed in the elongated cementite formed in the less deformed zone. This implies that rolling contact loading induced severe plastic deformation as well as a pronounced annealing effect in the active contact region of the toothed gear during cyclic loading.

Growth mode of austenite during reversion from martensite in Fe-2Mn-1.5Si-0.3C alloy: A transition in kinetics and morphology

The kinetics and element partitioning during austenite (γ) reversion from lath martensite in Fe-2Mn-1.5Si-0.3C (mass%) alloy have been investigated. Two different types of γ in terms of crystallography, with Kurdjumov-Sachs (K-S) and without K-S orientation relationships with respect to the surrounding tempered martensite matrix, are formed. A transition in kinetics and element partitioning is related to the differences in crystallography. At low temperature, the growth of both types of γ is accompanied with the partitioning of Mn and Si. Consequently, the growth rates and appearance of the K-S and non K-S γ are similar and the reverted γ structure consists of acicular γ dominantly. On the other hand, at high temperature, only the K-S γ grows with partitioning of alloying elements in contrast to the partitionless growth of the non K-S γ, which leads to the formation of coarse globular γ. DICTRA simulation reveals that the variations in driving force for reversion and the interface mobility induce the transition of element partitioning. At large driving force and interface mobility, partitionless growth is possible and consequently coarse globular γ is formed by the fast growth of the non K-S γ at high temperature. On the other hand, reduction of the driving force or interface mobility induces the transition from partitionless to partitioning growth, which results in the dominant formation of thin acicular γ at low temperature.

Investigation on Aging σ-Phase Precipitation Kinetics and Pitting Corrosion of 22 Pct Cr Economical Duplex Stainless Steel with Mn Addition

The influence of Mn addition on σ-phase precipitation kinetics and pitting corrosion of Fe-22Cr-1.9Ni-2.3Mo-0.2N-xMn low nickel type duplex stainless steel was investigated by medium- and high-temperature aging treatments of 600 °C and 800 °C. The microstructure analysis showed that the fine rod-shaped and coarsening dendritelike σ-phase precipitates formed at 600 °C and 800 °C, respectively, and the precipitate growth with the higher temperature was accelerated due to the partition of Mn, but Mn is not a strong σ-phase forming element like Cr, Mo during aging treatment at these two temperatures. At an early aging time of 800 °C, more precipitated nuclei with more Mn addition promote refinement of σ precipitates in later aging time. The kinetic behavior at 600 °C and 800 °C is related to diffusion-controlled growth of σ phase, and the σ-phase nucleation and growth are enhanced with more Mn addition and higher aging temperature due to a faster Mn diffusion rate. The difference in precipitation morphology for two aging temperatures was attributed to the different nucleation modes caused by kinetics parameter n variation. Increasing the aging temperature from 600 °C to 800 °C increased the susceptibility to pitting with higher Mn addition due to faster σ-phase precipitation kinetics.

Effect of Si on the partitioning of Mn between cementite and ferrite

ABSTRACTThe interlamellar spacings of pearlitic steels gradually increase as the isothermal transformation temperatures, correspondingly, the tensile strengths decrease, satisfying the Hall–Petch relationship. Si virtually completes its partitioning process during the eutectoid transformation. A depletion of Mn and an accumulation of Si are found in the concentration profiles of 0.95%-Si steel transformed at 793 K in the ferrite, but not in 0.22%-Si steel. It may attribute them to the Si–Mn diffusional flux couplings, which due to the strong interaction between Si and Mn atoms in the α-Fe. Transformation temperature increases to 873 K, a large amount of Mn atoms coming from ferrite cannot timely diffusion to cementite lamella core, forming a localised retention of Mn in the cementite phase side nearby the interface.This is part of a thematic issue on Pearlitic Steel Wires.

Partition and non-partition transition of austenite growth from a ferrite and cementite mixture in hypo- and hypereutectoid Fe-C-Mn alloys

The growth of austenite from a ferrite and cementite mixture in low Mn steel of hypo- and hypereutectoid composition is investigated with focus upon the Mn partitioning between dissolving cementite (or ferrite) and austenite. Under the assumption that austenite is nucleated on cementite, two critical temperatures which characterize the transition between Mn-partitioned and non-partitioned growth of austenite are noticed; below the 1st and lower critical temperature the austenite grows with redistribution of Mn from the beginning, and above the 2nd and higher critical temperature, without Mn redistribution until completion. Between them the growth mode switches from carbon-diffusion to Mn-diffusion control during growth. The influence of carbon and/or Mn diffusion through the matrix becomes progressively more significant with time, but may not affect the growth mode transition temperatures. Above the 2nd critical temperature, which is at most ca. 50 °C higher than Acm or Ae3 in alloys studied, the distribution of Mn in as-transformed or spheroidized pearlite is preserved at the completion of austenitization irrespective of the last dissolving phase, leading to the formation of an ultrafine mixture of martensite and austenite upon quenching.

Synergic effect of arbuscular mycorrhizal fungi and bradyrhizobia on biomass response, element partitioning and metallothionein gene expression of soybean-host under excess soil zinc

The synergic effect of rhizobia (R) and arbuscular mycorrhizal (AM) fungi on the bioproduction, trace element partitioning and metallothionein gene expression of soybean-host was investigated under normal and elevated soil zinc conditions. In a completely randomized 3×4 factorial design, the experimental treatments – Zn addition (0, 200, and 400 mg Zn kg−1 soil) and inoculation (uninoculated control, R, AM, and RAM dual inoculation) were set up in the greenhouse for nine weeks. While the inoculants effectiveness was decreased in 400 mg Zn kg−1 soils, RAM induced significantly higher biomass production under all soil Zn treatments. The biomass response indicated that AM modulated stem and root bioproduction in favor of leaf/pod, while rhizobium favored root production and potentiated AM effect in dual inoculation. The partitioning of Zn and Mn in the hosts indicated synergic effects between AM and R, in RAM plants. Compared with control, AM lowered leaf Zn concentrations by reducing root Zn concentrations and modulating root-to-stem and stem-to-leaf Zn translocations. Compared to AM, RAM plants achieved lower leaf and pod Zn concentrations by mainly reducing root-to-stem Zn translocation. Zn treatment increased leaf and pod Mn in control plants, but symbionts countered this by regulating root-to-stem Mn translocation, especially in RAM. Type 1 metallothionein gene expression in roots was highest in RAM and lowest in control plants, but Zn effects were not dose-dependent. Synergisms in symbionts root colonization, number and greenness of leaves, element partitioning and metallothionein gene expression are indicated as important mechanisms underlying the effective partnership between AM and R, in the dual inoculation.

Effect of C and N and their absence on the kinetics of austenite-ferrite phase transformations in Fe-0.5Mn alloy

Investigating the partitioning effect of substitutional and interstitial elements on the migration of transformation interfaces during austenite-ferrite phase transformation in steels with the conventional experimental method is extremely challenging due to interaction between the solute atoms and the transformation interfaces. Additionally, the simultaneous nucleation of new phases during phase transformations limits the accuracy of extracted growth rates from experimental kinetics measurements of phase fractions. In a novel experimental approach, the cyclic partial phase transformation concept is used to avoid the effect of nucleation on total kinetics of phase transformations. In this study, a Fe-0.5Mn alloy in the presence and absence of interstitial C and N additions is subjected to different cyclic transformation routes to examine the possible interaction between solute atoms and migrating interfaces. The experimental results are in semi-quantitative agreement with modelling predictions made by the local equilibrium approach and provide indirect evidence of Mn partitioning at austenite/ferrite interface in absence of any interstitial elements. It is also confirmed that the presence of interstitial elements promotes Mn interaction with the interface, whereas N promotes more Mn partitioning at transformation interface compared to C.

Effect of intercritical rolling temperature on microstructure-mechanical property relationship in a medium Mn-TRIP steel containing δ ferrite

We elucidate the influence of intercritical rolling temperature on the microstructural evolution, mechanical properties and work-hardening behavior of a hot-rolled Fe-0.2C-6.5Mn-3Al-0.1V medium Mn transformation-induced-plasticity (TRIP) steel containing δ-ferrite. Tensile strength of 966 MPa, total elongation of 42.6% and yield strength of 705 MPa was obtained in the annealed steel subjected to a low intercritical rolling temperature. Rolling at a high intercritical rolling temperature promoted the partitioning of Mn from δ ferrite to prior austenite grains, and led to a martensitic matrix characterized by a fine lath structure. Subsequently, after intercritical annealing, the reversed austenite transformed from the martensitic matrix had high stability and small size. However, the reversed austenite with a high degree of Mn enrichment, fine lath structure and high stability provided a slow and less active TRIP effect. This was responsible for low work-hardening rate during deformation. In contrast, the high content of reversed austenite in the annealed steel subjected to low intercritical rolling temperature had relatively low stability and large lath width, exhibited serrated work-hardening behavior indicative of discontinuous TRIP effect. Additionally, the low intercritical rolling temperature led to a high density of dislocations in δ-ferrite, which effectively promoted VC precipitation after intercritical annealing, and enhanced yield strength. Furthermore, the formation of high angle boundary in δ-ferrite and the formation of pro-eutectoid ferrite at low intercritical rolling temperature also enhanced yield strength through grain boundary strengthening.

Suspended particulate matter determines physical speciation of Fe, Mn, and trace metals in surface waters of Loire watershed

This study investigates the spatiotemporal variability of major and trace elements, dissolved organic carbon (DOC), total dissolved solids (TDS), and suspended particulate matter (SPM) in surface waters of several hydrosystems of the Loire River watershed in France. In particular, this study aims to delineate the impact of the abovementioned water physicochemical parameters on natural iron and manganese physical speciation (homoaggregation/heteroaggregation) among fine colloidal and dissolved (< 10nm), colloidal (10-450nm) and particulate (> 450nm) phases in Loire River watershed. Results show that the chemistry of the Loire River watershed is controlled by two end members: magmatic and metamorphic petrographic context on the upper part of the watershed; and sedimentary rocks for the middle and low part of the Loire. The percentage of particulate Fe and Mn increased downstream concurrent with the increase in SPM and major cations concentration, whereas the percentage of colloidal Fe and Mn decreased downstream. Transmission electron microscopy analyses of the colloidal and particulate fractions (from the non-filtered water sample) revealed that heteroaggregation of Fe and Mn rich natural nanoparticles and natural organic matter to the particulate phase is the dominant mechanism. The heteroaggregation controls the partitioning of Fe and Mn in the different fractions, potentially due to the increase in the ionic strength, and divalent cations concentration downstream, and SPM concentration. These findings imply that SPM concentration plays an important role in controlling the fate and behavior of Fe and Mn in various sized fractions. Graphical abstract Physical speciation by heteroaggregation of (Fe-Mn) compounds: high [SPM] → [Fe-Mn] particulate faction; low {SPM] → [Fe-Mn] colloid-dissolved fraction.

Partitioning and potential mobilization of aluminum, arsenic, iron, and heavy metals in tropical active and post-active acid sulfate soils: Influence of long-term paddy rice cultivation

Drainage of potential acid sulfate soils (PASS) for paddy rice cultivation results in the formation of active acid sulfate soils (AASS) and subsequently post-active acid sulfate soils (PAASS). The drainage of PASS causes severe environmental problems including acidification and metal contamination of soil and water resources. This study examined the vertical distribution and partitioning of Al, As, Co, Cu, Fe, Mn, Ni, Pb, and Zn in six tropical acid sulfate soils representing AASS and PAASS under long-term paddy rice cultivation (>145 years). The bulk soil samples were analyzed for total concentrations of Al, As, Co, Cu, Fe, Mn, Ni, Pb, and Zn. The partitioning of these elements was examined by a sequential extraction procedure. Labile Al is higher in ASS which is associated with low soil pH. During drainage, mobilization of As, Cu, and Pb is limited by coprecipitation with (poorly) crystalline Fe oxides minerals in the topsoil and partly oxidized layer of both soil types. These elements are associated with iron (mono) sulfides in unoxidized layer. When PASS are exposed to air, Co, Mn, Ni, and Zn are leached from the soils and are dominantly associated with iron sulfides in the unoxidized sediments. Labile Mn, Ni, and Zn are elevated in the unoxidized layer of PAASS because these elements are leached from the partly oxidized layers and adsorbed onto soil constituents. Cobalt is probably precipitated or adsorbed onto (poorly) crystalline minerals.

Nanoscale partitioning of Mn between austenite and martensite revealed by Curie temperature variations

The partitioning of Mn between deformation-induced martensite and austenite phases of a Fe−18Mn−2Al−2Si−0.04C high-Mn steel was studied by tracking variations in the Curie temperature of martensite after exposure to successively higher annealing temperatures. The increase in Curie temperature was justified by the Mn depletion of martensite. Assuming a linear relationship between the Curie temperature and Mn concentration, the average Mn concentration of martensite was expressed as a function of annealing temperature. The proposed method, which is applicable in a dilatometer with inductive heating, enables the ready estimation of Mn partitioning in intercritically annealed medium- and high-Mn steels.

Equilibrium Versus Paraequilibrium Precipitation of Cementite in Ternary Alloys: Thermodynamic and Kinetic Interpretations

The precipitation of cementite on decomposition of austenite is examined by an edgewise layer growth model of the carbide in Fe–1.2C wt% steels. The interface boundary can migrate into the supersaturated matrix isothermally at 400–600 °C, similar to tempering. The present paper thus explores precipitation mechanisms by two different kinetics. Intitially, an equilibrium growth, by the diffusional transport of atoms is simulated with the Dictra package accessing thermodynamic parameters from Thermo-calc. An extremely slow rate for the growth of the carbide platelet seems to be implausible due to the presence of the ternary [M = Mn, Si, Al] of 2 wt%. To overcome this, the investigation then finds an alternative, bringing diffusion constraints of the substitutional atoms under consideration in a paraequilibrium growth study. The SGTE database of the Thermo-calc however lacks paraequilibrium composition of Al in the carbide, thus Thermo-calc cannot be used thoroughly for this study. A first-principles calculation therefore is necessary which in turn evaluates the time-lag in equilibrium versus paraequilibrium growth kinetics. It reveals that the paraequilibrium precipitation of cementite is decisive due to Si (or Al) as the ternary, whereas, in the case of manganese steel, an opposite trend can be seen that the equilibrium partition of Mn reduces the Gibbs free energy during the interface study.