The Mössbauer Spectroscopy Studies οf Cementite Precipitations during Continuous Heating from As-Quenched State of High Carbon Cr-Mn-Mo Steel (original) (raw)
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Acta Physica Polonica A
This work presents results of investigations using the Mössbauer spectroscopy technique and their interpretation concerning transformation of to cementite carbides during tempering in relation to the previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The influence of the tempering time on nucleation and solubility of carbides, and on cementite nucleation and growth, was determined. The analysis of phase transformations during various periods of tempering using the Mössbauer spectroscopy technique made possible to reveal fine details connected with the processes.
Http Dx Doi Org 10 1080 14786435 2013 838010, 2013
The reaction between hematite and aluminum in presence of allumina as diluent activated by Ball Milling powder mixtures in different energetic conditions has been investigated. To this purpose, the powders at different milling times have been characterized by X-ray Diffraction and Mössbauer Spectroscopy. A self-substained combustion reaction was observed when the strongest energetic conditions of milling were adopted. The intermediate products of the reaction also depend on the energetic conditions: the formation of hercynite is favoured by the use of strong energetic conditions while the formation of an Fe-Al alloy was observed when a low energy per single hit is transferred to the powders.
Origin of Predominance of Cementite among Iron Carbides in Steel at Elevated Temperature
Physical Review Letters, 2010
A long-standing challenge in physics is to understand why cementite is the predominant carbide in steel. Here we show that the prevalent formation of cementite can be explained only by considering its stability at elevated temperature. A systematic highly accurate quantum mechanical study was conducted on the stability of binary iron carbides. The calculations show that all the iron carbides are unstable relative to the elemental solids, -Fe and graphite. Apart from a cubic Fe 23 C 6 phase, the energetically most favorable carbides exhibit hexagonal close-packed Fe sublattices. Finite-temperature analysis showed that contributions from lattice vibration and anomalous Curie-Weis magnetic ordering, rather than from the conventional lattice mismatch with the matrix, are the origin of the predominance of cementite during steel fabrication processes.
Cementite Formation from Magnetite under High Pressure Conditions
ISIJ International, 2013
Measurements have been made of the rate of Fe3C formation from Fe3O4 powder and Fe3O4 single crystals at 773 K and 1 023 K under the high pressure of 0.5 and 1.0 MPa by using thermo-gravimetric method. Along with the kinetic study of Fe3C formation, high resolution TEM observation around the interface between Fe3O4 matrix and the formed Fe3C have been carried out to confirm the thermodynamically possible direct Fe3C formation from Fe3O4 without the formation of intermediate metallic Fe. Analysis of the rate results suggests that the reaction mechanism of Fe3C formation was possibly described by the sequential reactions of the conversion of Fe3O4 to Fe3C via intermediate metallic Fe although the metallic Fe existence was not confirmed by TEM observation. This inconsistency was explained by considering the relative reaction rates of Fe3C formation from Fe and Fe formation from Fe3O4. It was also found that not only the carbon activity of more than unity but also the low oxygen potential enough for metallic Fe existence might be required for the Fe3C formation.
An atom probe study of cementite precipitation in autotempered martensite in an Fe-Mn-C alloy
Atom probe field ion microscopy has been used to determine the concentration profile of the substitutional solute element manganese through cementite particles in martensite in a ternary Fe-3Mn-0.1C (wt%) alloy. The start temperature of the martensite reaction (M s) in this alloy has been determined to be 380°C, which is relatively high. This means that as the specimen is quenched using helium gas, after austenitising, cementite particles are able to precipitate within the martensite plates which form at or near the M s temperature. The atom probe results revealed that, in the case of autotempered martensite, there is no significant partitioning of the manganese between the cementite and the supersaturated ferrite matrix.
Characterization of magnetic iron phases in IMPACTITES by MÖSSBAUER spectroscopy
Hyperfine Interactions, 2019
We present the results for two mineral samples from the Natural History Museum (MHN) of San Marcos National University (UNMSM) classified as: potential meteoritic samples coded MHN08 and MHN09 with an iron content of about 10% that were characterized using physical techniques such as energy dispersive X-ray fluorescence (EDXRF), X-ray diffractometry (XRD) and transmission Mössbauer spectroscopy (TMS). This study reveals that the samples consist mainly of quartz, goethite and impactites such as coesite, stishovite, and ringwoodite, and therefore should be classified as impactites. 57 Fe Mössbauer spectroscopy allowed the observation of three subspectra, two of them assigned to magnetic iron phases, and a third subspectrum assigned to a superparamagnetic phase. An important contribution of TMS is the possibility of observing this superparamagnetic phase which is assigned to goethite which at RT shows a very broad area (80.8%), and at liquid helium temperature appears as a magnetically ordered sextet.
Mossbauer Analysis of Low-Temperature Bainite
Low-temperature bainite, obtained by the transformation of austenite at temperatures as low as 200ºC for times as large as several days, has been reported to have extraordinary mechanical properties including the highest reported hardness of any bainitic steel. The unusual properties are a consequence of the fine scale of the microstructure, which contains bainite plates with thickness in the range 20-40 nm. The microstructure also contains carbon-enriched retained austenite which contributes to the properties via a number of mechanisms. In this work, the microstructure of a high carbon bainitic steel with Si to avoid cementite precipitation and Co to accelerate the transformation has been studied using Mössbauer spectroscopy for a series of samples transformed isothermally at 200ºC for time periods of 26, 34 and 96 hours. The total austenite content is almost identical (~13 wt%) for these samples although the carbon concentrations of the phases differ as a function of transformation time. The austenite increases its carbon content from 5.4 atomic % after 26 h transformation to 6.3 at.% after 96 h, while the final bainitic phase retains about 2.2 at.% of C. These results are consistent with data obtained using atom probe tomography for samples transformed isothermally for 12 days.
Mössbauer studies on steel samples
Journal of Engineering Sciences and Innovation
The paper presents the studies on the steels samples performed by Mössbauer spectroscopy. The 57 Fe isotope is most studied isotope by this method. The first studies were realized in the transmission geometry. Thus were studied industrial Fe-C steels, Fe-Si electrotechnical steels, the action of an organic inhibitor on the corrosion of OL37 steel and the compound formed at the Fe-Sn interface of a babbit bearing. The following studies were concentrated on the surface studies. The development of new detectors for surface studies was accomplish. The corrosion of industrial carbon steel in diluted ammoniacal media was studied. The inhibition effect of three organic compounds on the corrosion of carbon-steel in ammoniacal solutions was determined. The corrosion of industrial carbon steel in HCl solutions was investigated. The inhibition effect of five organic compounds for samples corroded in solutions of HCl were determined. Low carbon Fe-C steel surface has been studied before and after electrolytic galvanisation.
Journal of Magnetism and Magnetic Materials, 2014
The influence of the carbon content in form of globular cementite precipitates in unalloyed steels was macroscopically characterized by means of magnetic hysteresis loop and Barkhausen noise techniques. The choice of the frequency of the applied field has a strong influence on the Barkhausen noise profiles. At sufficiently high frequency (0.5 Hz) there are two peaks, one at lower field, the amplitude of which corresponds to the amount of ferrite and one at higher field, the amplitude of which corresponds to the amount of the cementite phase, respectively. Magnetic force microscopy and electron backscattered diffraction techniques were used to determine the magnetic and crystallographic microstructures of the steels. Cementite has its own domain structure and stray fields which influence the magnetization process of the steel by its own magnetic contribution. When an external magnetic field is applied, the magnetization process in ferrite occurs mainly at lower fields through the 180° and 90° domain walls. A higher field is required for the observation of 180° domain wall movements in cementite.