Solid state amorphization in a thin Fe-Si-Mg-O surface film triggered by the reduction of elements from oxides in the temperature range of the α-γ transformation

The study of the processes occurring in the surface layer of the MgO coated commercial alloy Fe-3%Si-0.5%Cu (grain oriented electrical steel) demonstrated that the amorphous phase in the form of a Fe-based solid solution is formed during continuous heating in the 95%N2 + 5%H2 atmosphere. For the purposes of this study, the following methods were used: non-ambient XRD at 20 –1060°C with heating and cooling at a rate of 0.5 dps, layer-by-layer chemical analysis performed by a glow discharge analyzer, scanning electron microscopy and energy dispersive X-ray spectroscopy. ThermoCalc software was used to calculate the potential phase equilibrium states. The amorphous phase was formed in the α → γ transformation temperature range, when the heating rates were altered in the surface layer of 1 µm initially consisted of a solid α-Fe-based solution with ~1– 2 wt.% Si with (MgFe)2 SiO4, (MgFe)O, SiO2 oxide inclusions. We suppose that (MgFe)2 SiO4 oxides are partly reduced by H2 to Mg2 Si molecular complexes, which become solid solutions in the temperature range of the metastability of the α-Fe crystal lattice with subsequent amorphization as an alternative to the α → γ transition. The amorphous state is obtained at 920 – 960°C and is retained both at subsequent heating (to 1060°C) and cooling (to 20°С), which is super-stable compared to the established metallic glasses. The composition of the amorphous phase can be described by the formula Fe89.5 Si6 Mg4 Cu0.5. © 2020, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Russian Foundation for Basic Research, RFBR: 20‑08‑00332Ministry of Education and Science of the Russian Federation, Minobrnauka: 11.1465.2014/K.Acknowledgements. This study was conducted using equipment provided by the Laboratory of Structural Analysis Techniques and Materials and Nanomaterials Properties of CKP Ural Federal University. The study was financially supported by Government Decree No. 211 of the Russian Federation, Contract No. 02. A03.21.0006 and within the framework of the state task issued by the Ministry of Education and Science of the Russian Federation, project No. 11.1465.2014/K. The reported study was funded by RFBR, project number 20‑08‑00332

Solid-State Amorphization Simulation in Thin Film of Fе–Si–Cu–Mg–O System

Solid-state amorphization process on Fe–3 %Si–0,5 %Cu alloy surface with thermostable MgO coating was observed at continuous annealing in 600–1060 °C temperature interval. Diffusion amorphization simulation has been suggested. Fe (Si) solid solution is being amorphizated because of Mg2Si complexes is transferring therein.Терморентгенографическим методом на поверхности сплава Fe-3 %Si–0,5 %Cu c термостойким покрытием MgO при непрерывном отжиге в интервале температур 600–1060 °C наблюдался процесс аморфизации из твердого состояния. Предложена модель диффузионной аморфизации твердого раствора Fe (Si) за счет перехода в него комплексов Mg2Si, образующихся в результате восстановления оксидов водородом

Formation of internal structure in the deformation zone during rolling of the BCC single crystal (110)[001]

Structure formation staging of a single crystal (110) [001] of the alloy with Fe – 3 % Si bcc was investigated directly in deformation zone during cold rolling. Laboratory rolling mill was abruptly stopped during the rolling of every sample to create a visible «de-formation zone». Lubrication was used on some samples to reduce the friction coefficient. Deformation structure was investigated by the methods of metallography and orientation electron microscopy. The connection of the experimental data with the calculated stress state was analyzed in Deform-3D program for different values of cold rolling friction coefficient. It was demonstrated that stress state in relation to friction coefficient can considerably influence the generation of mesostructure and crystal texture evolution in the material. It was observed that deformation bands formed in a cold rolled single crystal that was subject to high friction and relatively low strain value. Orientation analysis of the deformation bands linkage demonstrated in this area the existence of alternating microbands with slightly different orientations, separated from each other by low-angle boundaries. In case of single crystal (110)[001] rolling with lubrication (low friction) twinning was noted even for low strain level. As it seems, the reduction of surface energy input into the total energy of twin formation was the result of twinning. It was demonstrated that during all deformation process twins of both systems either preserved a strong Σ3 crystallographic connection with the matrix or Σ3 disorientation transformed into close special disorientations Σ17b and Σ43с in connection to local reorientation of crystal lattice. Based on experimental data dislocation model of deformation mesostructure formation during single crystal (110)[001] cold rolling has been proposed. This model deals with microbands formation at the initial stage of deformation bands appearance, the formation of transition bands parallel to rolling plane which retain initial orientations in dynamics, formation of transition bands tilted to the rolling plane with the habit planes parallel to {112} matrix planes. These transition bands are equivalent to shear bands the habit of which makes the angle of about 17° with the rolling plane. © 2017, National University of Science and Technology MISIS. All rights reserved