Fe-C Phase Research Articles

Study of Fe-C phase formulations through Fe self-diffusion during thin film growth

We studied diffusion process during the growth of Fe1−xCx (0≤x≤0.50) thin films at 300K. The broadening of an introduced 57Fe1−xCx thin layer obtained using secondary ion mass spectroscopy yielded concentration dependence of Fe self-diffusion. It suggests C occupies the grain boundary region and augments Fe self-diffusion. After a critical value of x≈0.04, it starts to slow down resulting in martensite phase and only amorphous Fe-C phases when x≥0.20. These were combined with x-ray diffraction, atomic force microscopy (AFM), x-ray absorption near-edge structure (XANES) at Fe-L2,3 and C K-edges, nuclear resonance scattering (NRS), SQUID vibrating sample magnetometer, and MOKE measurements. The local magnetic structure obtained using NRS reveals the formation of several phases including the martensite phase at the lower x to some fraction of the monoatomic FeC phase at the higher x. The XANES measurements show a charge transfer effect, indicating a self-organized multi-layered or clustered structure of phases. The surface morphology obtained from AFM measurements reveals the formation of clustered structures. The obtained results provide an important insight into the kinetics of iron carbide (Fe-C) phase formation and the influence of C concentration on the structural and magnetic properties of Fe-C thin films.

Analysis of the Formation Mechanism of Surface Cracks of Continuous Casting Slabs Caused by Mold Wear

Surface cracks are easily produced after friction between continuous casting billets and copper layers in mold cavity, but the formation mechanism is not clear. Based on a steel-based hot-dip copper plating experiment, this study simulated the action behavior of copper adhering to the surface of a continuous casting billet after mold wear and systematically analyzed the formation mechanism of cracks caused by copper infiltration on the surface of the continuous casting billet. It is shown that when the copper liquid adheres to the surface of the slab, in addition to the diffusion of Cu in the steel, Fe is also dissolved in the copper liquid, accelerating the solidification of the copper liquid on the surface of the slab and forming a stable fusion combination between copper and steel. At the same time, due to the enrichment of the Fe-C phase and a large number of vacancies at the grain boundary, the grain boundary becomes the dominant area of copper–steel fusion bonding. For a continuous casting process in which the temperature is kept higher than 900 ℃, Cu’s solubility is high and the diffusion coefficient is very low in Fe, which makes it very difficult for Cu accumulated in the grain boundary to diffuse into the steel matrix during the continuous casting process, resulting in a grain boundary with a greatly weakened strength becoming the origin of cracks in the bending and straightening deformation of the billet.

Modeling and Simulation of Vacuum Low Pressure Carburizing Process in Gear Steel

A combination of simulation and experimental approaches to optimize the vacuum carburizing process is necessary to replace the costly experimental trial-and-error method in time and resources. In order to accurately predict the microstructure evolution and mechanical properties of the vacuum carburizing process, a multi-field multi-scale coupled model considering the interaction of temperature, diffusion, phase transformation, and stress was established. Meanwhile, the improved model is combined with the heat treatment software COSMAP to realize the simulation of the low-pressure vacuum carburizing process. The low-pressure vacuum carburizing process of 20CrMo gear steel was simulated by COSMAP and compared with the experimental results to verify the model. The results indicated that the model could quantitatively obtain the carbon concentration distribution, Fe-C phase fraction, and hardness distribution. It can be found that the carbon content gradually decreased from the surface to the center. The surface carbon concentration is relatively high only after the carburizing stage. With the increase in diffusion time, the surface carbon concentration decreases, and the carburized layer depth increases. The simulated surface carbon concentration results and experimental results are in good agreement. However, there is an error between calculations and observations for the depth of the carburized layer. The error between simulation and experiment of the depth of carburized layer is less than 6%. The simulated surface hardness is 34 HV lower than the experimental surface hardness. The error of surface hardness is less than 5%, which indicates that the simulation results are reliable. Furthermore, vacuum carburizing processes with different diffusion times were simulated to achieve the carburizing target under specific requirements. The results demonstrated that the optimum process parameters are a carburizing time of 42 min and a diffusion time of 105 min. This provides reference and guidance for the development and optimization of the vacuum carburizing process.

Efficient estimation of material property curves and surfaces via active learning

The relationship between material properties and independent variables such as temperature, external field or time, is usually represented by a curve or surface in a multi-dimensional space. Determining such a curve or surface requires a series of experiments or calculations which are often time and cost consuming. A general strategy uses an appropriate utility function to sample the space to recommend the next optimal experiment or calculation within an active learning loop. However, knowing what the optimal sampling strategy to use to minimize the number of experiments is an outstanding problem. We compare a number of strategies based on directed exploration on several materials problems of varying complexity using a Kriging based model. These include one dimensional curves such as the fatigue life curve for 304L stainless steel and the Liquidus line of the Fe-C phase diagram, surfaces such as the Hartmann 3 function in 3D space and the fitted intermolecular potential for Ar-SH, and a four dimensional data set of experimental measurements for BaTiO3 based ceramics. We also consider the effects of experimental noise on the Hartmann 3 function. We find that directed exploration guided by maximum variance provides better performance overall, converging faster across several data sets. However, for certain problems, the trade-off methods incorporating exploitation can perform at least as well, if not better than maximum variance. Thus, we discuss how the choice of the utility function depends on the distribution of the data, the model performance and uncertainties, additive noise as well as the budget.

A study on the carbonization and alloying process of MnO2 by methane-hydrogen gas mixture in the presence of Fe2O3

Carbonization of pure MnO2 by CH4-H2 gas mixture with various CH4/(CH4+H2) molar ratios in the temperature range of 900–1250°C had been performed in our previous work. This study further investigated the carbonization and alloying process of MnO2 by CH4-H2 gas mixture in the presence of Fe2O3 at 900–1300°C using XRD, optical microstructure, SEM-EDS and phase diagram analyses. Carbonization test of pure Fe2O3 was also conducted to understand the effect of Fe2O3 on the carbonization of MnO2 more explicitly. It was found that Fe2O3 could be carbonized to Fe3C at 900–1150°C. The Fe2O3 briquettes began to melt at 1100°C and a large amount of Fe-C melts appeared as the temperature went up to 1150°C. When the MnO2+25 wt%Fe2O3 briquettes were reduced at 900–1000°C in CH4-H2 gas mixture, the Fe2O3 was preferentially carbonized to Fe-C phase while the MnO2 was only reduced to MnO. The formation of Fe-C phase was beneficial to the carbonization of MnO since the carbonization temperature of MnO can decrease from 1100°C to 1000°C. The carbonization degree of MnO was dramatically accelerated over 1100°C due to the transformation of Fe-C phase from solid state to melts. Morphology analysis indicated that the MnO core was wrapped by the shell of Fe-C melts. The alloying process of Mn-Fe-C was conducted through the elements migration of Fe and Mn between the core and shell. At 1300°C, the Mn-Fe-C alloy turned to melt and aggregated since the highest melting temperature of the Mn-C-25 wt% Fe system was only 1274°C. Finally, a ferromanganese crude alloy with 68–72wt% Mn, 20–25wt% Fe and 6.0–8.0wt% C was obtained when the MnO2+25wt% Fe2O3 briquettes were carbonized by CH4-H2 gas mixture at 1300°C for 60min.

Effects of precipitation and strain-induced martensitic transformation of Fe-C phases on the mechanical properties of Cu-Fe-C alloy

Effects of precipitation and strain-induced martensitic transformation of Fe-C phases on the mechanical properties of Cu-Fe-C alloy were systematically studied. The results reveal that, the hardness and strengths of Cu-Fe-C alloy can be increased after cold rolling, and forming shear bands in the alloy matrix. However, compared with directly cold rolling, the hardness, strengths and elongation can be all increased much more after using the processing of cold rolling 80%+heat treatment at 400°C for 60min+cold rolling 75%, which results from the contribution of both work hardening and precipitation strengthening of nano-sized α-Fe particles formed by strain-induced martensitic transformation. The formed α-Fe particles satisfy the K-S orientation relationship with Cu matrix, i.e. (011)α-Fe//(−111)Cu,[−11-1] α-Fe//[110]Cu. These findings provide inspiring using the martensitic transformation of Fe-C phases to improve mechanical properties of Cu-Fe-C alloys.

Diamond-bearing ophiolites and their geological occurrence

We document in this study the geological occurrence of diamonds and other ultrahigh-pressure (UHP) minerals in ophiolitic mantle peridotites and podiform chromitites from different orogenic belts. These minerals exist in both high-Cr and high-Al chromitites. Most ophiolite-hosted diamonds are small (∼ 200-500 μm across), and some contain distinctive inclusions (i.e., coesite, Ni-Mn-Co alloys, spessartite, tephroite). All of the analyzed diamonds have extremely light carbon isotope compositions (δ 13 C = -28.7 to -18.3‰) and variable trace element contents that distinguish them from most kimberlitic and UHP metamorphic varieties. A wide range of highly reduced minerals, such as native elements, Ni-Mn-Co alloys, Fe-Si and Fe-C phases and moissanite (SiC) also occuras accompanying mineral separates confirming the super-reducing conditions of their environment of formation. The presence of exsolution lamellae of diopside and coesite in some chromite grains suggests chromite crystallization depths around >380 km, near the mantle transition zone. Carbon and other recycled crustal materials at these depths are likely to have been derived from previously subducted material. The peridotites encapsulating the podiform chromitites and diamonds were transported to shallow mantle by convection cells beneath oceanic spreading centers. The chromitites may have formed in the deep mantle or in shallow suprasubduction zone environments. Our observations suggest that diamonds, UHP minerals and recycled crustal material are likely to be ubiquitous in the oceanic mantle.

Formation of chromium-alloyed cementite in the process of mechanosynthesis and subsequent annealings

Mossbauer spectroscopy and magnetic measurements have been used to investigate the formation of phases in the process of mechanosynthesis of a nanocomposite of composition (Fe0.93Cr0.07)75C25 in a planetary ball mill with the subsequent annealings at various temperatures. It has been shown that, at the initial stage of the mechanosynthesis, an amorphous Fe-C phase is formed. Later, an amorphous Fe-Cr-C phase is formed and, in the process of the subsequent mechanosynthesis, an alloyed cementite is formed from it. It has been found that, due to the products of the pickup from the milling balls made of ShKh15 steel, the changes in the initial composition (Fe0.93Cr0.07)75C25 of the powders that reach 5 wt % have almost no effect on the phase composition, specific saturation magnetization, and the coercive force of samples annealed at 800°C for 1 h.

Effect of Solute Elements and Cooling Rate on Strain in Brittle Temperature Range of Continuously Cast Strand

A micro-segregation model of solute elements in mushy zone with δ/γ transformation during solidification was established based on the regular hexagon transverse cross section of dendrite shape proposed by finite difference method under the non-equilibrium solidification condition. The model was used to calculate the non-equilibrium pseudo binary Fe-C phase diagram and the strain of steels induced by variation of temperature in brittle temperature range. On the basis of the phase diagram and the strain, the strain curve in brittle temperature range as a function of carbon content for continuously cast strand was introduced and obtained. Solute elements change the position of the strain curve. And cooling rate changes the position and the shape of the strain curve. The comprehensive formula of the strain as functions of solute elements and cooling rate in brittle temperature range has been obtained by nonlinear fitting program.

Carbon-bearing iron phases and the carbon isotope composition of the deep Earth

The carbon budget and dynamics of the Earth's interior, including the core, are currently very poorly understood. Diamond-bearing, mantle-derived rocks show a very well defined peak at δ(13)C ≈ -5 ± 3‰ with a very broad distribution to lower values (∼-40‰). The processes that have produced the wide δ(13)C distributions to the observed low δ(13)C values in the deep Earth have been extensively debated, but few viable models have been proposed. Here, we present a model for understanding carbon isotope distributions within the deep Earth, involving Fe-C phases (Fe carbides and C dissolved in Fe-Ni metal). Our theoretical calculations show that Fe and Si carbides can be significantly depleted in (13)C relative to other C-bearing materials even at mantle temperatures. Thus, the redox freezing and melting cycles of lithosphere via subduction upwelling in the deep Earth that involve the Fe-C phases can readily produce diamond with the observed low δ(13)C values. The sharp contrast in the δ(13)C distributions of peridotitic and eclogitic diamonds may reflect differences in their carbon cycles, controlled by the evolution of geodynamical processes around 2.5-3 Ga. Our model also predicts that the core contains C with low δ(13)C values and that an average δ(13)C value of the bulk Earth could be much lower than ∼-5‰, consistent with those of chondrites and other planetary body. The heterogeneous and depleted δ(13)C values of the deep Earth have implications, not only for its accretion-differentiation history but also for carbon isotope biosignatures for early life on the Earth.

The Study on Microstructure and Wear Resistance of In-situ Synthesis of TiAl(CN)/Fe Cermet Composite Coating

With Ti powder, Al powder and graphite powder as the coating material, and with industrial N2 as the shielding gas and reactive gas, the TiAl(CN)/Fe Cermet Composite Coating were prepared on the surface of Q235 steel base on Reactive Nitrogen Arc cladding by the TXII500 argon arc welding machine. The microstructure, phases and micro-hardness were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and MH-6 micro-hardness instrument. The wear loss of TiAl(CN)/Fe coating and 65Mn steel were analyzed and compared by HSR-2M friction and wear testing machine under room temperature dry sliding wear. The experiments show that the coating and the substrate forms metallurgical bond without stomata andcrack; the coating are composed of TiAl(C0.51N0.12) phase, AlFe3 phase,FeC phase; the micro-hardness of TiAl(CN)/Fecoating is 1110HV0.5 high, about 4 times of base metal; comparing with the 65Mn,the wear weight loss of TiAl(CN)/Fe coating is about 1/2 times, the wear resistance of TiAl(CN)/Fe coating is excellent. KeywordsIn-Situ Synthesis; Reactive Nitrogen Arc Cladding; Tial(CN) Cermet; Microstructure; Wear Resistance

309P - Does Administration Order of Sequential Fec- Docetaxel As Adjuvant Chemotherapy for Breast Cancer Affect on the Toxicities? : a Retrospective Analysis from a Single-Center

ABSTRACT Aim: Anthracyclines and taxanes based regimens have been established as one of standard adjuvant chemotherapy for early breast cancer. For the high-risk patients, sequential rather than the concomitant use of both agents should be considered.Conventionally, Anthracyclines followed by taxanes (AT) are preferred. However, some recent trials reported that preceding taxanes had equivalent efficacy. Since each has different toxic profile, it is important to compare AT with TA in terms of toxicity and relative dose intensity (RDI). The purpose of this retrospective study was to assess the influence of administration order. Methods: We analyzed 88 patients with early breast cancer who were treated with each 4 cycles of FEC (5-fluorouracil, epirubicin and cyclophosphamide) and Doc (docetaxel) as adjuvant chemotherapy. Consecutive 46 and 42 patients received FEC → Doc (AT group) From January to December of 2012 and Doc → FEC (TA group) for the same period of 2013, respectively. The data was collected from medical records, and toxicities were evaluated by CTCAE criteria. Statistical analysis was performed using Fisher's exact test. Results: There was no significant bias in patients' characteristics between both groups. Although the hematological toxicities seen in FEC and Doc phase were equal in both group, schedule delay of FEC were found more frequent in TA (19.0%) than AT (8.6%) because of insufficient recovery of neutropenia (p Conclusions: The administration of Doc before FEC results in reduced HFS by Doc, but RDI of FEC tends to decrease because of altered hematological toxicity. Evaluation of the prospective study is desired. Disclosure: All authors have declared no conflicts of interest.

Final analysis of the prospective WSG-AGO EC-Doc versus FEC phase III trial in intermediate-risk (pN1) early breast cancer: efficacy and predictive value of Ki67 expression

Taxane-based adjuvant chemotherapy is standard in node-positive (N+) early breast cancer (BC). The magnitude of benefit in intermediate-risk N+ early BC is still unclear. WSG-AGO epiribicine and cyclophosphamide (EC)-Doc is a large trial evaluating modern taxane-based chemotherapy in patients with 1-3 positive lymph nodes (LNs) only. A total of 2011 BC patients (18-65 years, pN1) were entered into a randomized phase III trial comparing 4 × E90C600 q3w followed by 4 × docetaxel 100 q3w (n = 1008) with the current standard: 6 × F500E100C500 q3w (n = 828) or C600M40F600 d1, 8× q4w (n = 175). Primary end point was event-free survival (EFS); secondary end points were overall survival (OS), toxicity, translational research, and quality of life. Central tumor bank samples were evaluable in a representative collective (n = 772; 40%). Ki-67 was assessed centrally in hormone receptor-positive disease as a surrogate marker for the distinction of luminal A/B-like tumors. Baseline characteristics were well balanced between study arms in both main study and central tumor bank subset. At 59-month median follow-up, superior efficacy of EC-Doc [versus FEC (a combination of 5-fluorouracil, epirubicin, and cyclophosphamide)] was seen in EFS and OS: 5-year EFS: 89.8% versus 87.3% (P = 0.038); 5-year OS: 94.5% versus 92.8% (P = 0.034); both tests one-tailed. EC-Doc caused more toxicity. In hormone receptor-positive (HR)+ disease, only high-Ki-67 tumors (≥ 20%) derived significant benefit from taxane-based therapy: hazard ratio = 0.39 (95% CI 0.18-0.82) for EC-Doc versus FEC (test for interaction; P = 0.01). EC-Doc significantly improved EFS and OS versus FEC in intermediate-risk BC (1-3 LNs) within all subgroups as defined by local pathology. In HR+ disease, patients with luminal A-like tumors may be potentially over-treated by taxane-based chemotherapy. ClinicalTrials.gov, NCT02115204.

Theoretic analysis on the mechanism of particular pattern formed on the ancient Damascus steel blades

What causes the specific pattern on the ancient Damascus steel blades has been a myth for centuries and is still a hot topic for the today’s metallurgist. Although it has been studied and argued for centuries, the disputes on this topic still remain among the present metallurgists, which are summarized in this paper. Besides, histories of Wootz ingots, Damascus blade and Damascus pattern have been also reviewed respectively in details. With the help of modern metallurgy knowledge, we are now able to quantify all the possibly relevant factors by thermodynamic and kinetic calculations, such as influence of S, P and V elements on the Fe-C phase diagram, the dendritic microsegregation of S and P during a slow solidification, the temperature for precipitation of V(CN) in austenite and the diffusion kinetics of V during high-temperature homogenization. All of those factors have been considered as the possible perquisites for the formation of Damascus pattern. The thermodynamic and kinetics simulations indicate that the sulfide and phosphide, which precipitates at the segregated zone due to the slow solidification, may not be completely dissolved at the high-temperature solution treatment and then might act as the nuclei for the subsequent precipitation of cementite particles during hot hammering. In particular, the P-rich liquid, which is formed due to the segregation during solidification, may transform to eutectic product of phosphide and cementite. This is most likely responsible for the spatial distribution of cementite in Damascus blades and the formation of Damascus pattern.

The electrochemical reactions of pure indium with Li and Na: Anomalous electrolyte decomposition, benefits of FEC additive, phase transitions and electrode performance

Indium thin films were evaluated as an anode material for Li-ion and Na-ion batteries (theoretical capacities of 1012 mAh g−1 for Li and 467 mAh g−1 for Na). XRD data reveal that several known Li–In phases (LiIn, Li3In2, LiIn2 and Li13In3) form providing 950 mAh g−1 reversible capacity. In contrast, the reaction with Na is severely limited (75–125 mAh g−1). XRD data of short-circuited cells (40 h at 65 °C) show the coexistence of NaIn, In, and an unknown NaxIn phase. In electrodes exhibit anomalous electrolyte decomposition characterized by large discharge plateaus at 1.4 V vs Li/Li+ and 0.9 V vs Na/Na+. The presence of 5 wt% fluoroethylene carbonate additive suppresses the occurrence of the electrolyte decomposition during the first cycle but does not necessarily prevent it upon further cycling. Prevention of the anomalous decomposition can be achieved by restricting the (dis)charge voltages, increasing the current or by using larger amounts of FEC. The native surface oxides (In2O3) are responsible for the pronounced electrolyte decomposition during the first cycle while other In3+ species are responsible during the subsequent cycles. We also show that indium electrodes can exhibit very high rate capability for both Li (100 C-rate) and Na (30 C-rate).

Formation and Structure of Graphene Waves on Fe(110)

A very rich Fe-C phase diagram makes the formation of graphene on iron surfaces a challenging task. Here we demonstrate that the growth of graphene on epitaxial iron films can be realized by chemical vapor deposition at relatively low temperatures, and that the formation of carbides can be avoided in excess of the carbon-containing precursors. The resulting graphene monolayer creates a novel periodically corrugated pattern on Fe(110). Using low-energy electron microscopy and scanning tunneling microscopy, we show that it is modulated in one dimension forming long waves with a period of ∼4 nm parallel to the [001] direction of the substrate, with an additional height modulation along the wave crests. The observed topography of the graphene/Fe superstructure is well reproduced by density functional theory calculations, and found to result from a unique combination of the lattice mismatch and strong interfacial interaction, as probed by core-level photoemission and x-ray absorption spectroscopy.

Extended Tensile Ductility of a Formable High-Performance High-Manganese Steel

The aim of the contribution is to review the structure/property relationship of a high-performance FeMnN steel composition. In this work the influence of the Mn content ranging from 12 wt.-% to 24 wt.-% on the Fe-C phase diagram was calculated by thermodynamic simulations. The influence of coiling temperature on the microstructure of the FeMnN steel was studied by annealing treatments from 350 °C up to 750 °C. It showed the possible presence of cementite and martensite/pearlite after long annealing treatments at temperatures close to 500 °C. The steel was observed to exhibit outstanding combinations of tensile strength and ductility. The FeMnN steel exhibited at room temperature a remarkably high total elongation of about 100 % with a high tensile strength level of 1100 MPa. This product, proportional to toughness, achieved an outstanding value of about 110000 %MPa. The extended tensile ductility of the high-performance FeMnN steel was attributed to the nano-size twinning induced plasticity (NS-TWIP), which was observed by in-depth transmission electron microscopy study.

Time-Resolved X-Ray Diffraction Study on Solidification of Fe-B and Fe-C Eutectic Alloys

Solidification processes of Fe-B and Fe-C eutectic alloys have been investigated by a time-resolved synchrotron x-ray diffraction under containerless cooling conditions using a conical nozzle levitation technique. To observe relative variations of structure from the undercooled liquid to crystalline phase, we have conducted millisecond order time-resolved x-ray diffraction experiments with a two-dimensional detector. The structural variations observed during the solidification of the Fe83C17 alloy were identified as the phase transformation process expected from the Fe-C phase diagram. As for the Fe83B17 alloy, it was revealed that a metastable phase composed of Fe23B6 compound was precipitated as a primary crystalline phase from the undercooled liquid. In addition, decomposition of the metastable Fe23B6 phase showed dependence on the cooling rate of the sample. At the cooling rate of 30 K/s, the Fe23B6 phase decomposed to bcc-Fe and Fe2B phases with decreasing temperature. On the contrary, at the cooling rate of 180 K/s, the metastable Fe23B6 phase remained in spite of an appearance of the bcc-Fe phase. By comparing the primary crystalline phase between the Fe83C17 and the Fe83B17 alloys, we suggest that the formability of the metastable Cr23C6-type compound is closely related with the glass-forming ability of Fe-metalloid binary alloys.

Synthesis of large-area, few-layer graphene on iron foil by chemical vapor deposition

We demonstrate a simple and controllable way to synthesize large-area, few-layer graphene on iron substrates by an optimized chemical vapor deposition (CVD) method using a mixture of methane and hydrogen. Based on an analysis of the Fe-C phase diagram, a suitable procedure for the successful synthesis of graphene on Fe surfaces was designed. An appropriate temperature and cooling process were found to be very important in the synthesis of highly crystalline few-layer graphene. Graphene-based field-effect transistor (FET) devices were fabricated using the resulting few-layer graphene, and showed good quality with extracted mobilities of 300–1150 cm2/(V·s). Open image in new window

Foreword: Symposium on Austenite Formation and Decomposition IV

The technological importance of ferrous alloys rests to a large extent on their relatively low cost and their ability to achieve desirable strength-ductility combinations. The attainment of superior properties depends to a large degree on the phase transformations to and from austenite that occur during processing. From a scientific standpoint, ferrous alloys have been and continue to be benchmark materials from which solid-solid phase transformations understanding, broadly considered, was first formulated and developed. Since pioneering studies began in the 1880s, significant advances in this understanding have been made in view of developments such as the first Fe-C phase diagram (1900), x-ray diffraction (1920s), T-T-T diagrams (1930s), classical nucleation-and-growth theory (1940s), theories of martensite (1950s), and electron microscopy (1950s).