scholarly journals Microstructure and Microtexture Development in Grain Oriented Electrical Steel

2021 ◽  
Author(s):  
◽  
Ali Nadoum
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Heating Rate ◽  
Grain Growth ◽  
Electrical Steel ◽  
Flow Direction ◽  
Rolling Direction ◽  
Magnetic Domain ◽  
Abnormal Grain Growth ◽  
Heat Flow Direction

The first Si-Fe electrical steel was produced in 1905, and the grain-oriented steel was discovered in 1930 after Goss demonstrated how optimal combinations of heat treatment and cold rolling could produce a texture giving Si-Fe strip good magnetic properties when magnetised along its rolling direction. This technology has reduced the power loss in transformers greatly and remains the basis of the manufacturing process today. Since then, many postulations reported on the mechanism on abnormal grain growth (AGG) which is the key for Si-Fe superior magnetic properties. However, none have provided a concrete understanding of this phenomenon. Identifying and classifying the driving force behind Goss abnormal grain growth is of industrial and academic importance to further optimise the manufacturing process and reduce losses. In the current investigation, the deviation from easy magnetisation direction <001> was studied to find a correlation between crystallographic orientation and magnetic domain structure. Both deviation angles α: the angle between <001> and in-plane rolling direction (RD), and β: the angle between <001> and out-plane rolling direction were calculated using electron backscatter diffraction (EBSD) raw data. Further, EBSD combined with forescatter detector (FSD) is used to reveal the magnetic domain configuration within individual oriented grains. The magnetic domain patterns were directly imaged and correlated to the crystal orientation and α and β deviation angles. It was demonstrated that the size of the deviated orientation grains from ideal (110) <001> Goss orientation is a critical microtexture parameter for the optimisation of magnetic property. It is concluded that the magnetic domain patterns and α and β angle of deviations are strongly correlated to the magnetic losses in GOES (grain oriented electrical steel).Furthermore, the effect of grain boundaries, grain size, heating rate and dislocation density on Goss abnormal grain growth was investigated using EBSD. It was found that in the early stages of secondary recrystallisation random grains grow and abnormal growth of Goss achieved in low heating rate. The advantage of Goss abnormal grain growth in secondary recrystallisation is lost while annealing at a high heating rate, and random orientation can grow abnormally. Also, statistical analysis of grain boundaries, including CSL (coincident site lattice), shows no distinct behaviour and high angle grain boundaries and CSL are not exclusive to Goss oriented grains. In addition, GND (geometrically necessary dislocation) and Taylor Factor showed to be randomly distributed around Goss grains, and the hypothesis of Goss grains grow by consuming high GND and Taylor Factor grains cannot be the reason for Goss abnormal grain growth. Neutron diffraction experiment was conducted at Rutherford Appleton Laboratory, ISIS facility at Oxford, UK using GEM beamline. It was demonstrated that Si atom positions in the solid solution disorder α-Fe cubic unit cell that cause lattice distortions and BCC symmetry reduction is the most influential factor in early stages of Goss AGG than what was previously thought to be dislocation related stored energy, grain boundary characteristics and grain size/orientation advantages. Finally, heat flux, heat flow direction, and strain effect on Goss abnormal grain growth investigated. It was found that heat flow direction greatly impacts the rate of abnormal grain growth of Goss. Also, strain areas can disrupt Goss AGG and promotes randomly oriented grains to grow abnormally.

Influence of Heating Rate and Decarburization Temperature on the Microstructure and Magnetic Properties of Grain Oriented Electrical Steel

2012 ◽  
Vol 706-709 ◽  
pp. 2622-2627 ◽  
Author(s):  
Chun Kan Hou ◽  
Jian Ming Tzeng
Keyword(s):  
Magnetic Properties ◽  
Heating Rate ◽  
Grain Growth ◽  
Electrical Steel ◽  
Rapid Heating ◽  
Abnormal Grain Growth ◽  
Heating Rates ◽  
Abnormal Growth ◽  
Steel Sheets ◽  
Microstructure And Magnetic Properties

Effects of three heating rates, 5, 20/min., and 300°C/sec and decarburization temperature, 700-850°C in primary annealing on the microstructure and magnetic properties of a grain oriented electrical steel were investigated. It was found that the oxide layer thickness and grain size increased with increasing decarburization temperature. However, they decreased with increasing heating rate. On the other hand, injection nitrogen content into steel sheets decreased with increasing decarburization temperature. The percentage of abnormal grain growth obtained a peak value at 800°C in the specimens treated with heating rate less than 20°C per minute. But specimens with rapid heating rate, percentage of abnormal grain growth increased with increasing decarburization temperature. As percentage of abnormal growth increased, magnetic properties got better.

Abnormal Grain Growth in Electrochemically Deposited Cu Films

2004 ◽  
Vol 467-470 ◽  
pp. 1339-1344 ◽  
Author(s):  
Matthias Militzer ◽  
P. Freundlich ◽  
D. Bizzotto
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Experimental Studies ◽  
Abnormal Grain Growth ◽  
Grain Structure ◽  
Additive Concentration ◽  
Organic Additives ◽  
Plating Bath ◽  
Cu Films

Cu interconnects are essential in advanced integrated circuits to minimize the RC delay. In manufacturing these devices, Cu is deposited electrochemically using a plating bath containing organic additives. The as-deposited nanocrystalline Cu films undergo self-annealing at room temperature to form a micronsized grain structure by abnormal grain growth. Systematic experimental studies of self-annealing kinetics on model Cu films deposited on a Au substrate suggest that the rate of grain size evolution depends primarily on the initial grain size of the asdeposited film. A model for the observed abnormal grain growth process is proposed. Assuming that desorption of the organic additives leads to mobile grain boundaries, the onset of abnormal grain growth is attributed to a sufficiently low additive concentration such that a full coverage of all grain boundaries cannot be maintained. The incubation time of abnormal growth is then a logarithmic function of the initial grain size. The probability to find a growing grain is proportional to the number of grains per unit volume. This assumption is seen to be in good agreement with the experimental observations for subsequent abnormal grain growth rates. The limitations of the proposed model and the challenges to obtain further insight into the complex microstructure mechanisms during self-annealing are delineated.

scholarly journals Kinetics of Austenite Grain Growth during a Continuous Heating of a Niobium Microalloyed Steel

2004 ◽  
Vol 467-470 ◽  
pp. 929-934 ◽  
Author(s):  
David San Martín ◽  
Francisca García Caballero ◽  
Carlos Capdevila ◽  
C. Carcía de Andrés
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Heating Rate ◽  
Grain Growth ◽  
Continuous Heating ◽  
Second Phase ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Average Grain Size ◽  
The Matrix

Grain growth is a thermally activated process in which the average grain size increases as temperature and time increases. The driving force for grain growth results from the decrease in the free energy associated with the reduction in total grain boundary energy. There are several known factors that influence the migration of grain boundaries such as second phase particles precipitated in the matrix and the solute elements segregated at grain boundaries. The austenite grain boundaries are revealed using the thermal etching method. Carbon extraction replicas were prepared to determine the composition and size of precipitates present in the matrix. In this work, the evolution of the average prior austenite grain size (PAGS) of a low carbon steel microalloyed with niobium is studied as a function of temperature and heating rate. Austenite grains show a two-stage growth. It has been found that as heating rate increases, the grain coarsening temperature (TGC) increases and the grain size at that temperature decreases. TGC temperature lies around 40-60°C below the temperature for complete dissolution of carbonitrides (TDISS).

scholarly journals Precipitates in Compact Strip Production (CSP) Process Non-Oriented Electrical Steel

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1301
Author(s):  
Jia-long Qiao ◽  
Fei-hu Guo ◽  
Jin-wen Hu ◽  
Li Xiang ◽  
Sheng-tao Qiu ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Electrical Steel ◽  
Volume Fraction ◽  
Precipitation Mechanism ◽  
Compact Strip Production ◽  
Transmission Electron ◽  
Average Size ◽  
Strip Production

Nitrogen and Sulfur in non-oriented electrical steel would form precipitates, which would severely affect its magnetic properties. Precipitates in compact strip production (CSP) process non-oriented electrical steel were investigated using a transmission electron microscope (TEM) and scanning electron microscopy (SEM). The precipitation mechanism and influence on grain growth were analyzed experimentally and theoretically. The results showed that the main particles in steel were AlN, TiN, MnS, Cu2S, and fine oxide inclusions. The spherical or quasi-spherical of MnS and Cu2S were more liable to precipitate along grain boundaries. During the soaking process, the amount of MnS precipitated on the grain boundary was much larger than that of Cu2S. AlN and TiN in cubic shape precipitated inside grains or grain boundaries. Precipitates preferentially nucleated at grain boundaries, and TiN, MnS mainly precipitated during soaking. In the subsequent processes after soaking, AlN and Cu2S would precipitate unceasingly with the decrease in the average size. The distribution density, the volume fraction, and the average size of the precipitates in the annealed sheets were 9.08 × 1013/cm3, 0.06%, and 54.3 nm, respectively. Precipitates with the grain size of 30–500 nm hindered the grain growth, the grains with 100–300 nm played a major role in inhibiting the grain growth, and the grains with the grain size of 70–100 nm took the second place.

scholarly journals Mean Field Analysis of Orientation Selective Grain Growth Driven By Interface-Energy Anisotropy

1994 ◽  
Vol 343 ◽  
Author(s):  
J. A. Floro ◽  
C. V. Thompson
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Growth ◽  
Texture Evolution ◽  
Mean Field ◽  
Orientation Distribution ◽  
Interface Energy ◽  
Abnormal Grain Growth ◽  
Field Analysis ◽  
Energy Anisotropy

ABSTRACTAbnormal grain growth is characterized by the lack of a steady state grain size distribution. In extreme cases the size distribution becomes transiently bimodal, with a few grains growing much larger than the average size. This is known as secondary grain growth. In polycrystalline thin films, the surface energy γs and film/substrate interfacial energy γi vary with grain orientation, providing an orientation-selective driving force that can lead to abnormal grain growth. We employ a mean field analysis that incorporates the effect of interface energy anisotropy to predict the evolution of the grain size/orientation distribution. While abnormal grain growth and texture evolution always result when interface energy anisotropy is present, whether secondary grain growth occurs will depend sensitively on the details of the orientation dependence of γi.

A Role of Low Energy Grain Boundaries in the Abnormal Grain Growth in Fe-3%Si Alloy

2011 ◽  
Vol 127 ◽  
pp. 89-94 ◽  
Author(s):  
Ye Chao Zhu ◽  
Jiong Hui Mao ◽  
Fa Tang Tan ◽  
Xue Liang Qiao
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Electron Backscatter Diffraction ◽  
Dominant Role ◽  
Coincidence Site Lattice ◽  
Diffraction Method ◽  
Abnormal Grain Growth ◽  
Low Energy ◽  
Backscatter Diffraction

Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.

Mechanism of Grain Growth During Annealing of Si-Al Electrical Steel Strips Deformed in Tension

2010 ◽  
Vol 1276 ◽  
Author(s):  
J. Salinas B ◽  
A. Salinas R
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Electrical Steel ◽  
Electron Backscatter Diffraction ◽  
Steel Strip ◽  
Boundary Migration ◽  
Primary Recrystallization ◽  
Steel Strips ◽  
Grain Orientation Spread ◽  
Quality Maps

AbstractThe mechanism of recrystallization as a result of annealing during 600–7200 seconds at 700 °C of a Si-Al, low C electrical steel strip is investigated in samples deformed in tension. The evolution of grain size during annealing is evaluated by optical microscopy and electron backscatter diffraction in the scanning electron microscope. It is found that grain growth starts after an incubation time of 600 s with no apparent evidence of primary recrystallization. After that, the grain size-time relationship exhibits two different stages. Initially, the grain size increases linearly with time up to about 3600 s. During this time, some selected grains grow until they consume the deformed microstructure. In the second stage, the rate of growth decreases significantly and a final grain size of about 150 m is reached after 7200 seconds of annealing. Grain orientation spread maps obtained from EBSD data of deformed and partially recrystallized samples during the stage of linear growth reveals that the growing grains exhibit lower misorientation and therefore smaller stored energy than the non-recrystallized matrix grains. Analysis of image quality maps reveal that the IQ values for {100}<uvw>orientations are higher than those observed for {111}<uvw>orientations thus suggesting that the {100}<uvw>orientations grow at the expense of {111}<uvw>orientations by a mechanism of strain-induced boundary migration.

An Overview of Accomplishments and Challenges in Recrystallization and Grain Growth

2007 ◽  
Vol 558-559 ◽  
pp. 33-42 ◽  
Author(s):  
Anthony D. Rollett ◽  
Abhijit P. Brahme ◽  
C.G. Roberts
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Degrees Of Freedom ◽  
Driving Forces ◽  
Excess Free Energy ◽  
Abnormal Grain Growth ◽  
Process Models ◽  
Three Dimensions ◽  
Polycrystalline Materials ◽  
General Process

The study of microstructural evolution in polycrystalline materials has been active for many decades so it is interesting to illustrate the progress that has been made and to point out some remaining challenges. Grain boundaries are important because their long-range motion controls evolution in many cases. We have some understanding of the essential features of grain boundary properties over the five macroscopic degrees of freedom. Excess free energy, for example, is dominated by the two surfaces that comprise the boundary although the twist component also has a non-negligible influence. Mobility is less well defined although there are some clear trends for certain classes of materials such as fcc metals. Computer simulation has made a critical contribution by showing, for example, that mobility exhibits an intrinsic crystallographic anisotropy even in the absence of impurities. At the mesoscopic level, we now have rigorous relationships between geometry and growth rates for individual grains in three dimensions. We are in the process of validating computer models of grain growth against 3D non-destructive measurements. Quantitative modeling of recrystallization that includes texture development has been accomplished in several groups. Other properties such as corrosion resistance are being related quantitatively to microstructure. There remain, however, numerous challenges. Despite decades of study, we still do not have complete cause-and-effect descriptions of most cases of abnormal grain growth. The response of nanostructured materials to annealing can lead to either unexpected resistance to coarsening, or, coarsening at unexpectedly low temperatures. General process models for recrystallization that can be applied to industrial alloys remain elusive although significant progress has been made for the specific case of aluminum alloy processing. Thin films often exhibit stagnation of grain growth that we do not fully understand, as well as abnormal grain growth. Grain boundaries respond to driving forces in more complicated ways than we understood. Clearly many exciting challenges remain in grain growth and recrystallization.

The Influence of High Magnetic Field on the Stability of CryoECAPed 1050 Alloy

2013 ◽  
Vol 774-776 ◽  
pp. 968-973
Author(s):  
Yi Heng Cao ◽  
Li Zi He ◽  
Xiao Tao Liu ◽  
Hai Tao Zhang ◽  
Ping Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Grain Size ◽  
Diffraction Pattern ◽  
Grain Growth ◽  
High Magnetic Field ◽  
Hardness Test ◽  
Abnormal Grain Growth ◽  
Back Scattering ◽  
The Stability

The evolutions of mechanical properties and microstructure of cryoECAPed 1050 alloy annealed at various temperatures from 150°C to 400°C for 1h with and without high magnetic field (HMF) were investigated by hardness test and electron back scattering diffraction pattern (EBSD) analysis. The abnormal grain growth happens in sample annealing at 400°C without a field. With the application of high magnetic field, the formation of the HABs is suppressed, the grain size distribution is homogeneous and no abnormal grain growth occurs.

Investigation of the Sintering Behavior of Ultrapure α-Alumina Containing Low Amounts of SiO2 or CaO

2006 ◽  
Vol 317-318 ◽  
pp. 1-6 ◽  
Author(s):  
Nicolas Louet ◽  
Thierry Epicier ◽  
Gilbert Fantozzi
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Oxygen Vacancies ◽  
Glassy Phase ◽  
Intermediate Stage ◽  
Abnormal Grain Growth ◽  
Sintering Behavior ◽  
Critical Temperatures ◽  
Heterogeneous Microstructures

The target of this work is to investigate the effect of small additions of SiO2 or CaO on the sintering behavior and the microstructure of an ultrapure α-alumina compound. The sintering behavior has been investigated through extensive dilatometric study. SiO2 additions lead to a significant decrease in shrinkage rate during the intermediate stage of sintering whereas CaO is beneficent to densification. It has been found that during this stage which corresponds to the maximum of densification rate, grain boundaries diffusion controls densification through oxygen vacancies. The study of the densification behavior under different atmospheres help us to explain the role of the additives in agreement with electroneutrality equations. S.E.M. investigations confirm the well know correlation between doping and heterogeneous microstructures. After doping with SiO2 or CaO, abnormal grain growth appears at temperatures corresponding to the lowest eutectics given by Al2O3-SiO2 or Al2O3-CaO phase diagrams. H.R.T.E.M. observations show that below the critical temperatures for abnormal grain growth, additives enrichment is observed near grain boundaries (GBs). Above these temperatures, glassy phase for SiO2-doping and calciumhexaluminate (CA6) for CaO-doping are present at grain boundaries.

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