Initial Stages Of Recrystallization Research Articles

A comprehensive study on texture evolution and recrystallization mechanism of Fe-4.5 wt% Si with strong {114}

Improving both the magnetic properties and strength of non-oriented electrical steel used in driving motors of new energy vehicles is a great challenge. In this study, a 4.5 wt% Si non-oriented electrical steel that had a strong {114}<481> texture and exhibited excellent magnetic and high strength, was produced via hot rolling, cold rolling and annealing. The texture evolution of hot-rolled plate with strong Goss and medium strength λ-fiber ({100}<0vw>) was investigated in detail during rolling and annealing. The VPSC model was used to simulate the texture evolution during the rolling process, of which the neff model could satisfactorily explain the classical rotation route of Goss and Cube. At the initial stage of recrystallization, the orientation of the recrystallized grains, characterized by electron backscatter diffraction (EBSD), was closely related to the orientation of the hot-rolled plate and rotation path during the rolling process. This clear evidence indicated that the initial recrystallized grains were oriented nucleation. During the recrystallization process, the characterization of specific orientations by quasi-in-situ EBSD revealed that the unusual {114}<481> was formed by an oriented growth mechanism. Texture evolution during the recrystallization indicated oriented nucleation as an inherent property responsible for the initial recrystallization texture, while oriented growth was influenced by deformed grain size and grain boundary characteristics.

ON THE MECHANISM OF MINERAL NANOMETRY

In our time, the manifestation of significant interest in natural mineral individuals of nanometric dimensions has become natural and necessary. A new branch of geological science, nanomineralogy, has also been developed. An analysis of the data accumulated on this problem made it possible to speak of two ways for the formation of natural nanosized crystals: a) crystallization and b) deformation. The first of them, crystallization, is the natural origin of the crystallization of any mineral individual in its characteristic initial period. Convictions are expressed that all crystalline particles — germs — have nanosizes, and all minerals began their development from nanocrystals. The appearance of individuals of this size is also characteristic of the initial stages of recrystallization of volcanic glasses. Nanoscale values are characteristic, for example, of opals. The second way is deformational, when the development of geological matter is determined by the peculiarities of tectonic evolution, its geodynamics.

Texture Evolution during Recrystallization and Grain Growth in Non-Oriented Electrical Steel Produced by Compact Strip Production Process.

Evolution of texture and α*-fiber texture formation mechanism of Fe-0.65%Si non-oriented electrical steel produced by Compact Strip Production (CSP) process during all the thermo-mechanical processing steps were investigated using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) techniques. Columnar crystal structure of cast slab is fine and well-developed. Textures of the hot-rolled band are quite different in the thickness direction. During annealing of cold-rolled sheet, γ-fiber texture grains would nucleate and grow preferentially, and α*-fiber texture grains mainly nucleate and grow in the shear zone of α-fiber texture of cold-rolled sheet. During the recrystallization process, γ-fiber texture gradually concentrated to {111}<112>, and γ and α*-fiber texture increased significantly. {111}<112> texture priority nucleation at the initial stage of recrystallization. Due to the advantages of nucleation position and quantity, the content of α*-fiber texture is greater than {111}<112> texture in the mid-recrystallization. During grain growth process, {111}<112> oriented grains would grow selectively by virtue of higher mobility, sizes and quantity advantages than that of {411}<148 > and {100}<120>, resulting in the gradual increase of γ-fiber texture and the decline of α *-fiber texture.

Effects of Trace Amounts of Mn, Zr and Sc on the Recrystallization and Corrosion Resistance of Al-5Mg Alloys

This study aimed to explore the effects of trace amounts of Mn, Zr, and Sc on the recrystallization behavior and corrosion resistance of Al-5Mg alloys after process annealing by means of alloy design and microstructure analysis of electron backscatter diffraction (EBSD), electron microprobe (EPMA), and electron microscopes (TEM and SEM). The main objective was to obtain alloys with better corrosion resistance. The results show that the fine Al3Zr and Al3Sc precipitated particles were both superior to the MnAl6 particles in inhibiting grain and sub-grain boundary migrations. Therefore, the Zr-containing and Sc-containing alloys were better than the Mn-containing alloy in inhibiting recrystallization. For further comparison, the thermal stability of the Al3Sc particles was better than that of the Al3Zr particles, so the Sc-containing alloy at the high temperature above 350 °C inhibited grain growth better than the Zr-containing alloy. During the recovery stage of the alloy in the recrystallization process, the β-Mg2Al3 phase precipitated on the sub-grain boundary, thus reducing the occurrence of intergranular corrosion. However, in the initial stage of recrystallization, the β-Mg2Al3 phase continuously precipitated on the grain boundary, causing obvious intergranular corrosion. For the Sc-containing alloy, because there was no obvious grain growth stage, the β-Mg2Al3 phase continuously precipitated on the grain boundary, and thereby intergranular corrosion occurred. Therefore, its corrosion resistance was greatly reduced. By contrast, for the alloy containing Mn or Zr, because of obvious grain growth, magnesium atoms aggregated. As a result, the β-Mg2Al3 phase discontinuously precipitated on the grain boundary. The corrosion morphology was local pitting corrosion rather than intergranular corrosion, and thus the corrosion resistance of the alloy was enhanced. As a novelty, this study clearly observed the sensitized precipitation and corrosion morphology of the β-Mg2Al3 phase of Al-5Mg alloy under different recrystallization methods. This will be of benefit to the design of anti-corrosion measures for the future manufacturing and application of Al-5Mg alloy.

Effect of cooling rate on long-term recrystallized crystal of rice starch in the presence of flavor compounds

This study evaluated the effect of cooling rate on starch recrystallization in the presence of 2,3-butanedione and 2-acetyl-1-pyrroline, which could form B-type and V-type complexes with starch, respectively. Rapid cooling resulted in poor perfection and high heterogeneity of both B-type and V-type recrystallized crystal. For B-type crystal, rapid cooling changed nucleation mode from instantaneous (Avrami index n < 1) to continuous mechanism (1 ≤ n ≤ 2), and decreased recrystallization rate from 0.0502 to 0.0160 d−n, indicating the increased retention of starch on 2,3-butanedione. V-type crystal was formed at initial stages of recrystallization, and inhibited the growth of B-type crystal. The loose crystalline obtained by rapid cooling is conducive to the retention of flavor compounds for B-type complexes (especially ≤14 days) and V-type complexes (especially ≤1 day). These results could provide guidance for maintaining fragrance of instant rice during long-term storage.

Observations of Point Defect Dynamics in the Recrystallization of Cold-rolled Tungsten Foils

The evolution of point defects with annealing temperature is investigated in cold-rolled tungsten samples using positron annihilation spectroscopy and transmission electron microscopy. We report a correlation between the unexpectedly high intensity of mono-vacancy-like lifetime (201 ps) observed at 1373 K annealing temperature and the initial stages of recrystallization. The formation of large vacancy clusters is also observed at higher annealing temperatures (~ 2000 K), well beyond the defect recovery temperature in tungsten.

Effect of vanadium on the precipitation strengthening upon tempering of a high-strength pipe steel with different initial structure

Methods of metallography, scanning electron, and transmission electron microscopies were used to study the structure of two pipe steels (without vanadium and with 0.03% vanadium) subjected to γ → α isothermal transformation at temperatures of 400–600°C (initial structure) and tempering at 600–650°C. It has been found that the addition of 0.03% vanadium intensifies the process of the precipitation of ferrite and contributes to the formation of a granular structure. It has been shown that, in high-strength pipe steels with 0.03% vanadium, which have bainitic granular-type structures, the effect of the precipitation strengthening is effected upon subsequent high-temperature tempering at 600–630°; the addition of vanadium leads to an increase in the hardness by 16 HV. In the presence of bainite of the lath type in the initial structure, the subsequent tempering leads to a softening associated with the processes of the recovery, polygonization, and initial stages of recrystallization in situ, which develops at temperatures above 640°C. It has been found that the hardness of the steel without vanadium upon additional tempering decreases regardless of the morphology of structural constituents in the initial structure.

Effect of Thermal Action on Low-Carbon and Silicon-Manganese Steel Microstructure and Properties

The change in microstructure is considered for silicon-manganese and low-carbon steels under conditions modeling prolonged thermal action. Metal structure and property degradation is revealed. It is shown that prolonged thermal action creates conditions for the occurrence of thermal deformation ageing, the initial stage of recrystallization, and also pearlite spheroidization.

Effect of Twinning on Microstructural Evolution During Dynamic Recrystallisation of Hot Deformed As-Cast Austenitic Stainless Steel

An as-cast austenitic stainless steel was hot deformed at 1173 K, 1223 K, and 1373 K (900 °C, 950 °C, and 1100 °C) to a strain of 1 with a strain rate of 0.5 or 5 s−1. The recrystallised fraction is observed to be dependent on dynamic recrystallisation (DRX). DRX grains nucleated at the initial stages of recrystallization have similar orientation to that of the deformed grains. With increasing deformation, Cube texture dominates, mainly due to multiple twinning and grain rotation during deformation.

Recrystallization in Finite 3-D Dust Clouds

The recrystallization process of a finite dust cloud is studied experimentally on the kinetic level. The temporal evolution of the coupling parameter allows to reveal that the cluster is molten while laser heated and recrystallizes when heating is switched OFF. The cooling rate can be deduced from the initial stage of recrystallization.

Microstructure and Texture Evolutions in a Short-Time-Annealed Interstitial-Free Steel

One kind of high strength interstitial free steel sheets are annealed in a salt bath at 810 C for different times (1-30 s). The microstructure and recrystallized texture evolution during annealing are investigated using the optical microscopy and the Electron Back Scattered Diffraction technique. The results show that beginning and finishing of recrystallization are observed in the sample annealed at 810 C for 8 and for 20 s, respectively. The recrystallized grains nucleate in the order of ‹111›//ND, ‹110›//ND and ‹100›//ND. Recrystallized grains with ‹111›//ND orientation nucleate firstly in the ‹111›//ND deformed grains as well as at their boundaries and grow up by consuming the ‹111›//ND deformed grains at the initial stage of recrystallization. The ‹111›//ND recrystallized grains grow up by depleting the remained formed ‹100›//ND grains after the full consumption of the ‹111›//ND deformed grains. The overall recrystallization texture is mainly the ‹111›//ND component in the steel.

Particle Stimulated Nucleation in Coarse-Grained Ferritic Stainless Steel

Particle-stimulated nucleation (PSN) is investigated in Nb-containing ferritic stainless steel. Coarse-grained sheets were cold rolled to 80 pct thickness reduction and annealed from 973 K to 998 K (700 °C to 725 °C) to obtain partially recrystallized microstructures. Electron backscatter diffraction was performed around coarse niobium carbonitride particles (larger than 1 μm) within coarse grains (~1 mm), with different host orientations in both deformed and annealed states. In the deformed state, the deformation zones around both spherical and rectangular particles were investigated. The local lattice rotations about the transverse direction necessary to accommodate the particle-matrix strain incompatibility were observed in all grains investigated. After annealing, recrystallization occurs preferentially around coarse particles at the initial stages of recrystallization. Based on a total number of 130 grains nucleated via PSN, we observe both, randomly oriented and minor {111}〈110〉 oriented texture components. The results also reveal that PSN in this material is not associated with a specific host orientation.

Effect of Magnetic Field Direction on Texture Evolution in Cold-Rolled IF Steel Sheet at the Initial Stage of Recrystallization

Sheets of cold rolled (76%) IF steel were annealed at 650°C for 30min under a 12-tesla magnetic field. During the magnetic field annealing, they were placed at the center of the applied field respectively, being oriented differently with respect to the magnetic field direction. The results show that the high magnetic field annealing prevents the evolution from deformed {111}&lt;110&gt; texture component to recrystallized {111}&lt;112&gt; texture component at the initial stage of recrystallization. For the field annealed specimens, altering the specimen orientation to the magnetic field direction during annealing does not change the final annealing textures. The intensity of main {111} texture components presents a similar periodic variation with respect to the specimen orientation to the magnetic field.

Grain refinement by cold deformation and recrystallization of bainite and acicular ferrite structures of C–Mn steels

The propensity of bainite and acicular ferrite structures of experimental C–Mn steels for enhanced grain refinement by combining phase transformation and plastic deformation has been investigated. Formation of acicular ferrite structures were stimulated with a small amount of titanium and titanium oxide nanoparticles added into the molten steels of high Mn concentrations. Isothermal transformations into the bainite and acicular ferrite structures were performed for 1.8ks at 823K after preliminary austenitization for 1.8ks at 1523K. Cold rolling for 50% thickness reduction was conducted on the isothermally transformed structures. Subsequent annealing of the deformed structures was conducted for 3.6ks at 773, 873 and 973K. Optical microscopy, scanning electron microscopy and tensile test were used for characterization of the studied steels. Cold rolling and annealing of the transformed structures at 873K resulted in strengthening at the expense of ductility where an initial stage of recrystallization is realized. Acicular ferrite obtained by the addition of titanium into the molten steel exhibited the remarkable improvement of tensile properties. Discontinuous recrystallization of the deformed structures at 973K leads to the formation of fine grains wherein acicular structures represented more enhanced grain refinement than bainite.

Orientation Mapping Study on the Inhomogeneous Microstructure Evolution during Annealing of 6013 Aluminum Alloy

Orientation mapping in transmission electron microscope was successfully applied to study microstructural changes at the initial stage of recrystallization in the aluminum alloy with a bimodal second-phase particle distribution. The alloy samples were reversibly cold rolled resulting in the formation of laminar structure with zones of localized strain around large second-phase particles. Orientation mapping and in-situ investigations carry information about the processes which are active in the deformation zones during annealing.

Effects of High Magnetic Field Annealing on the Nucleation Sites for Recrystallized Nuclei with {111} &amp;lt;112&amp;gt; Orientation in Cold-Rolled IF Steel Sheet

The effect of high magnetic field annealing on the nucleation sites for recrystallized nuclei with {111}&lt;112&gt; orientation in the initial stage of recrystallization in as-annealed interstitial-free (IF) steel sheet were investigated by the SEM-EBSD analysis. Specimens of cold rolled IF steel sheet were annealed at 650°C for 0min and 10min respectively with a 12-tesla magnetic field to obtain a partially recrystallized microstructure. During the magnetic field annealing, they were respectively placed at the center of the applied field with their rolling planes parallel to the magnetic field direction (MD), and with their rolling direction (RD) parallel and normal to the MD, respectively. It was found that different to the non-field annealed specimen, in the field annealed specimens, the {111}&lt;112&gt; oriented recrystallized nulei favored to nucleate in the {111}&lt;112&gt; deformed matrix and not in the {111}&lt;110&gt; deformed matrix. This phenomenon may be attributed to the magnetic ordered state induced by the magnetic field, which might suppress the formation of high-energy grain boundaries between the newly formed nuclei and the deformed matrix.

Activated Slip Systems and Nucleation of Recrystallized Grains in Aluminium Deformed in Channel-Die

The relations between the active slip systems within the deformed state and the orientations of the first formed nuclei of recrystallized grains have been studied in strongly deformed samples of high purity aluminium single crystal and polycrystalline aggregates. The new grain orientations and misorientations were followed by systematic local orientation measurements using SEM-FEG/EBSD and semi-automatic measurements in TEM. Investigations of the direction of growth indicate the privileged role of {111} planes in the initial stages of recrystallization. The grain boundary migration and ‘consumption’ of the as-deformed areas was always favoured along directions parallel to the traces of the most active {111} slip planes as shown clearly in the stable and structurally homogeneous Goss{110}&lt;001&gt; oriented crystallite. In the case of polycrystalline material the influence of grain boundaries and their triple junctions on the crystallographic aspects of nucleation is discussed.

Effects of High Magnetic Field and Field Direction on Recrystallization and Recrystallization Texture in Cold-Rolled IF Steel Sheet

The effects of magnetic annealing on recrystallization and texture evolution in asannealed interstitial-free (IF) steel sheet were investigated by means of X-ray diffraction ODF analysis, SEM-EBSD analysis, and optical microstructure observation. During the magnetic annealing, specimens were placed at the center of the applied magnetic field, with their rolling planes parallel to the field direction (MD) and their rolling direction (RD) normal to the field direction (MD). It was found that the magnetic annealing retards the recrystallization process, but promotes the nucleation at the initial stage of recrystallization. Magnetic annealing did not change the mechanism of recrystallization texture evolution but improved the development of γ-fiber texture during the process of recrystallization, and the magnetically annealed specimen had stronger γ-fiber texture compared with the conventionally annealed specimen; this interesting finding is quite different from the previous work on magnetically annealed IF steel.

Texture and Microstructure Evolution of Gold Sheet during Deformation and Annealing

Texture and microstructure of gold sheet were investigated during deformation and subsequent annealing. The Brass, S and Copper (β-fiber) orientations are closely connected together in the deformed microstructure. Recrystallization texture also was examined during isothermal annealing at 500°C with reduction in area. Initial rolling textures with rotated cube and β-fiber resulted in the cube and recrystallized β-fiber orientations after annealing. A two dimensional Monte Carlo (MC) method was used to simulate primary recrystallization in gold sheet. A function of boundary misorientation was introduced to consider anisotropic properties of grain boundary energy and mobility. Stored energy associated with orientations in the deformed grains was evaluated by reconstructing of data measured using electron back-scattered diffraction (EBSD). The nucleation at an initial stage of recrystallization was found at the high angle grain boundaries (HAGBs) and grain interiors. The main texture components obtained by the simulation were similar to those obtained experimentally except cube component.

Texture Evolution during Annealing of Warm Rolled Cr-Containing Low Carbon Steels

Two low carbon steels alloyed with 0.48wt% and 0.78wt% Cr were warm rolled to 65% reduction at 640°C. Annealing was carried out at 710°C to achieve a range of recrystallized volume fractions up to 100%. Texture analysis was performed by X-ray diffraction and Electron Back Scattering Diffraction. During the initial stages of recrystallization, more recrystallized grains nucleated at shear bands than at grain boundaries in the 0.48wt%Cr steel, whereas this was not the case in the 0.78wt%Cr steel. This is associated with a decrease in the propensity to form shear bands due to the lower amount of C in solid solution in the high-Cr steel. Additionally, the nuclei showed a preference to develop the same fiber as the deformed region within which they nucleated. In both steels, an increase in the annealing time led to the deterioration of the ND (or γ) –fiber and a strengthening of both the RD (or α) –fiber and Goss component. In the fully recrystallized samples, the ND component was somewhat stronger in the steel with the higher Cr content.