Investigation of Primary Recrystallization and Decarbonization with Different Heating Rates of Intermediate Annealing Using Nb-Containing Grain-Oriented Silicon Steel

An Nb-containing grain-oriented silicon steel was produced through double-stage cold rolling in order to investigate the effect of the heating rate during intermediate annealing on primary recrystallization and decarburization behavior. The microstructure and texture were observed and analyzed by an optical microscope and an electron backscatter diffraction system. A transmission electron microscope was used to observe the precipitation behavior of inhibitors. The decarburization effect during intermediate annealing was also calculated and discussed. The results show that primary recrystallization takes place after intermediate annealing. As the heating rate increases, the average grain size decreases gradually. The textures of {411}<148> and {111}<112> were found to be the strongest along the thickness direction in all of the annealed specimens and are mainly surrounded by HEGB and HAGB (> 45°). A large number of inhibitors with the size of 14~20 nm precipitate are distributed evenly in the matrix. The above results indicate that the higher heating rate during intermediate annealing contributes to both an excellent microstructure and magnetic properties. From the calculation, as the heating rate increases, decarbonization tends to proceed in the insulation stage, and the total amount of carbonization declines.

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Influence of Temperature on Typical Texture Distribution in Primary Recrystallization Matrix of 3% Si CGO Silicon Steel

Advances in Materials Science and Engineering ◽

10.1155/2016/8936805 ◽

2016 ◽

Vol 2016 ◽

pp. 1-6

Author(s):

Zhi-chao Li ◽

Ning Dang ◽

Zhen-li Mi

Keyword(s):

Grain Boundaries ◽

Annealing Temperature ◽

Secondary Recrystallization ◽

Fiber Texture ◽

Primary Recrystallization ◽

Silicon Steel ◽

Recrystallization Annealing ◽

Intermediate Annealing ◽

High Angle ◽

Goss Texture

OM (optical microscopy) and EBSD (electron backscatter diffraction) techniques were used to study microstructure and texture distribution during primary recrystallization under different intermediate annealing temperatures in CGO silicon steels. The effect of intermediate annealing temperature on texture distribution in 3% Si electrical steel was analyzed. The results indicate that the microstructure in primary recrystallization matrix of CGO silicon steel is comprised of equiaxed ferrite grains. Mean grain size of primary recrystallization increases with the rising of intermediate annealing temperature.γ-fiber texture is the dominant component in primary recrystallization matrix. With higher intermediate annealing temperature,111121texture and111110texture increase and111121texture is stronger than111110texture. Goss texture was observed to be decreased firstly and then increased. The content of high angle grain boundaries in primary recrystallization matrix are affected by intermediate annealing temperature. When intermediate annealing temperature is increased, high angle grain boundaries are increased firstly and then decreased. Misorientation distribution in primary recrystallized matrix is affected by primary recrystallization annealing temperature either. The content of high angle grain boundaries are increased owing to higher primary recrystallization annealing temperature, which can be a benefit to the abnormal growth of Goss grains in secondary recrystallization.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.467-470.929 ◽

2004 ◽

Vol 467-470 ◽

pp. 929-934 ◽

Cited By ~ 2

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).

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Effect of heating rate of final annealing stage on secondary recrystallization in grain-oriented silicon steel

Metallurgical Research & Technology ◽

10.1051/metal/2020063 ◽

2020 ◽

Vol 117 (6) ◽

pp. 607

Author(s):

Lifeng Fan ◽

Xingyuan Zhao ◽

Rong Zhu ◽

Jianzhong He ◽

Yuan Xiang Zhang

Keyword(s):

Heating Rate ◽

Texture Component ◽

Secondary Recrystallization ◽

Average Diameter ◽

Silicon Steel ◽

Medium Temperature ◽

Goss Texture ◽

Final Annealing ◽

Average Grain Size ◽

Component Form

A grain-oriented silicon steel sheet was manufactured by slab reheated at “medium temperature” and two-stage cold rolling method. The function of heating rate on secondary recrystallization in grain-oriented silicon steel was investigated. The results show that: compared with 30 °C/h heating rate, the initial temperature of the secondary recrystallization can increase by 10 °C at the heating rate of 20 °C/h. Furthermore, the temperature region of secondary recrystallization also extended either with the increased heating rate. Even though the inhibitors maintain AlN, complex precipitation of AlN and sulphide in both heating rate, the average diameter and Zener factor of inhibitors are distinct. Inhibitors in the route of 20 °C/h heating rate express stronger inhibition than that of 30 °C/h, and the average diameter and Zener factor are 17.519 nm and 3.925 × 10−4 nm−1, respectively. In addition, more Goss texture component and less γ-fiber texture ({111}//ND) component form at the heating rate of 30 °C/h than 20 °C/h at 1000 °C, but the final Goss texture component of 20 °C/h is greater than 30 °C/h. The average grain size of the final annealing sheets increased with the heating rate decreasing from 30 °C/h to 20 °C/h, and iron loss reduced by 0.05 W/Kg, the magnetic induction intensity increased by 0.025 T.

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Study of Deformation Behavior and Microstructural Evolution in Multiphase Steel

Materials ◽

10.3390/ma11112285 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2285 ◽

Cited By ~ 1

Author(s):

Jun Lu ◽

Hao Yu ◽

Xiaoni Duan ◽

Chenghao Song

Keyword(s):

High Performance ◽

Tensile Deformation ◽

Electron Backscatter Diffraction ◽

Bainitic Ferrite ◽

Tensile Tests ◽

Dislocation Configuration ◽

Transmission Electron ◽

Average Grain Size ◽

The Matrix ◽

Multiphase Steel

In the present work, the tensile deformation characteristics of the high performance multiphase steel with complex microstructures are investigated. A mixture of ferrite, bainite, and 14.4 vol% retained austenite (RA) with an average grain size of less than 3 μm of the matrix is obtained after specific heat treatment. Tensile tests are performed with increasing strain, i.e., 0%, 5%, 10%, 15%, and 20%. Then X-ray diffraction, transmission electron microscope and electron backscatter diffraction are utilized to analyze the deformation-transformation behaviors of the complex microstructures. Phase transformation of the RA, which is controlled by its morphology and distribution, contributes to high strain hardening capacity of the steel. The blocky-type RA that locates in ferrite grain boundaries shows less stability and transforms easily at early deformation stage, while the film-like RA that distributes between bainitic ferrite shows higher stability and transforms continuously throughout plastic deformation. Moreover, the substructure formation by dislocation configuration in ferrite grains begins with randomly distributed dislocations and ends up with cellular structures, resulting in ferrite subdivision during deformation and also grain refinement strengthening. As a result, the experimental steel is reinforced not only by the martensite transformation of RA, but also ferrite refinement.

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Microstructural Control of Dual Phase Structure Formed by Partial Reversion from Cold-Deformed Martensite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.753.191 ◽

2013 ◽

Vol 753 ◽

pp. 191-194 ◽

Cited By ~ 1

Author(s):

Nobuo Nakada ◽

Yusuke Arakawa ◽

Kyo Sun Park ◽

Toshihiro Tsuchiyama ◽

Setsuo Takaki

Keyword(s):

Heating Rate ◽

Microstructural Development ◽

Dual Phase ◽

Low Carbon ◽

Heating Rates ◽

Dp Structure ◽

The Matrix ◽

Fresh Martensite ◽

Rolling Rate ◽

Partial Reversion

Dual phase (DP) structure formed by partial reversion from cold-deformed martensite was investigated to improve mechanical property of DP steel by grain refinement strengthening. A low carbon martensitic steel (0.15C-1.0Mn) was cold-rolled and then held just above A1 temperature to partially form austenite. In particular, the conditions of cold-rolling rate (0~60% reduction in thickness) and heating rate (0.083 and 100 K/s) were varied to understand their effects on the microstructural development of DP structure. Although the recrystallization has never occurred in undeformed martensite, cold-deformed martensite was more easily recrystallized before reversion with increasing rolling rate and lowering heating rate. Then, the matrix of DP structure was changed from tempered martensite to recrystallized ferrite, which had a large influence on the distribution of fresh martensite transformed from reversed austenite. The higher rolling and heating rates resulted in the finer DP structure, leading to a large improvement in strength level.

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Superplastic Behavioral Characteristics of Fine-Grained 5A70 Aluminum Alloy

Metals ◽

10.3390/met9010062 ◽

2019 ◽

Vol 9 (1) ◽

pp. 62 ◽

Cited By ~ 4

Author(s):

Sheng Li ◽

Zhongguo Huang ◽

Shunyao Jin

Keyword(s):

Grain Boundaries ◽

Electron Backscatter Diffraction ◽

Energy Dispersive Spectrometer ◽

Rate Sensitivity ◽

Alloy Sheet ◽

Second Phase ◽

Fine Grained ◽

Transmission Electron ◽

Average Grain Size ◽

The Matrix

A fine-grained 5A70 alloy sheet was obtained through a combination of rolling and heat treatment, with a total deformation reduction of 90% and an average grain size of 8.48 μm. The alloy was studied at 400, 450, 500, and 550 °C and exhibited excellent elongation-to-failures of 205, 321, 398, and 437% with coefficients for the strain rate sensitivity of 0.42, 0.40, 0.47 and 0.46, respectively. Electron backscatter diffraction (EBSD) results revealed that the massive grain boundaries were high angle boundaries, suggesting that boundary sliding and grain rotation occurred during superplastic deformation. The X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) results indicated that the compositions were the Al6(MnFe) and Mg-rich phase particles of the deformed 5A70 alloy. In addition, the weakening of the pinning effect led to abnormal grain growth at 500 and 550 °C, resulting in strain hardening. Transmission electron microscopy (TEM) examinations demonstrated that the applied stress at the head of the precipitated particles and/or grain boundaries exceeded the matrix-structure-promoted cavity nucleation. Cavities grew, interlinked, and coalesced, which resulted in crack formation that eventually led to superplastic fractures. Filaments formed at the fracture surfaces because of second phase precipitation at grain boundaries and the formation of Mg-rich oxides.

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The Localized Corrosion and Stress Corrosion Cracking of a 6005A-T6 Extrusion Profile

Materials ◽

10.3390/ma14174924 ◽

2021 ◽

Vol 14 (17) ◽

pp. 4924

Author(s):

Jijun Ma ◽

Jing Sun ◽

Quanmei Guan ◽

Qingwei Yang ◽

Jian Tang ◽

...

Keyword(s):

Grain Boundaries ◽

Stress Corrosion ◽

Stress Corrosion Cracking ◽

Electron Backscatter Diffraction ◽

Optical Microscope ◽

Corrosion Cracking ◽

Localized Corrosion ◽

Interfacial Engineering ◽

The Matrix ◽

Crack Tips

In the present work, the localized corrosion and stress corrosion cracking (SCC) behaviors of a commercial 6005A-T6 aluminum extrusion profile was studied comprehensively. The velocity of crack growth in self-stressed double-cantilever beam (DCB) specimens under constant displacement was estimated, which also provides insight into the local microstructure evolutions at the crack tips caused by the localized pitting corrosion, intergranular corrosion (IGC), and intergranular SCC. Characterizations of local corrosion along the cracking path for a period of exposure to 3.5% NaCl were revealed via optical microscope (OM), scanning electron microscope (SEM), and electron backscatter diffraction (EBSD). The typical features of the pits dominated by the distribution of precipitates included the peripheral dissolution of the Al matrix, channeling corrosion, intergranular attack, and large pits in the grains. The discontinuous cracking at the crack tips indicated the hydrogen-embrittlement-mediated mechanism. Moreover, the local regions enriched with Mg2Si and Mg5Si6 phases and with low-angle grain boundaries presented better SCC resistance than those of the matrix with high-angle grain boundaries, supporting a strategy to develop advanced Al–Mg–Si alloys via interfacial engineering.

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The microstructure change of low-carbon electrical steels by residual aluminum

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100153403 ◽

1989 ◽

Vol 47 ◽

pp. 286-287

Author(s):

C.K. Hou ◽

C.T. Hu ◽

Sanboh Lee

Keyword(s):

Annealing Treatment ◽

Low Carbon ◽

Electrical Steels ◽

Vacuum Degassing ◽

Spherical Inclusions ◽

Residual Aluminum ◽

Average Grain Size ◽

The Matrix ◽

Fine Size ◽

To Come

The fully processed low-carbon electrical steels are generally fabricated through vacuum degassing to reduce the carbon level and to avoid the need for any further decarburization annealing treatment. This investigation was conducted on eighteen heats of such steels with aluminum content ranging from 0.001% to 0.011% which was believed to come from the addition of ferroalloys.The sizes of all the observed grains are less than 24 μm, and gradually decrease as the content of aluminum is increased from 0.001% to 0.007%. For steels with residual aluminum greater than 0. 007%, the average grain size becomes constant and is about 8.8 μm as shown in Fig. 1. When the aluminum is increased, the observed grains are changed from the uniformly coarse and equiaxial shape to the fine size in the region near surfaces and the elongated shape in the central region. SEM and EDAX analysis of large spherical inclusions in the matrix indicate that silicate is the majority compound when the aluminum propotion is less than 0.003%, then the content of aluminum in compound inclusion increases with that in steel.

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