Goss Orientation Research Articles

Effect of solution time on microstructure, texture and mechanical properties of Al–Mg–Si–Cu alloys

Effect of solution time on the microstructure, texture and mechanical properties of Al–Mg–Si–Cu alloy sheets with different contents of iron-rich phase was investigated systematically by microstructure characterization, texture measurement and tensile test. The results show that the recrystallization microstructure, texture and mechanical properties can be affected by the change of solution time, but the level depends on the content and distribution of iron-rich phase. With increasing solution time, the strengths and planar anisotropy Δr values of the sheets increase, but plasticity strain ratio r and strain-hardening exponent n values decrease, the change in values is much more significant in alloy with low volume fraction of iron-rich phase than those of alloy with high number of iron-rich phase. The same trend for the changes of recrystallization grain size of the two alloys can also be observed. Additionally, the texture of the sheet with low volume fraction of iron-rich phase particles transforms from Cube orientation to CubeND and P orientations firstly, and finally transforms to Goss orientation with further increasing solution time, whereas the texture of the sheet with a high number of iron-rich phase particles only transforms from Cube orientation to CubeND and P orientations even after long time solution treatment. Accordingly, the effect of texture on r value has been simulated and one recrystallization model is proposed to explain the recrystallization texture evolution.

Deformation, recovery and recrystallization from heterogeneous shear bands in steel sheets

In order to clarify the mechanism of Goss texture formation along shear bands, the effect of cold rolling reduction on shear band formation and crystal orientation within shear bands and annealing texture were investigated in Fe-3%Si {111}<112> single crystals. Shear bands were formed intermittently during cold rolling; shear bands with smaller angles were formed earlier and those with larger angles were formed later. This result supports geometrical softening as a mechanism for shear band formation. Crystal rotation along shear bands became large in proportion to reduction. In calculation crystal rotation in ideal matrix, (111)[11-2], did not reach Goss, however, with consideration of orientation fluctuation the rotation angle exceeded Goss orientation and it coincided with the experimental data. After annealing recrystallized grains along shear bands were mainly Goss grains regardless of cold rolling reduction. The speculated reason for the dominance of Goss during annealing is that Goss cells have a comparatively lower density of dislocations and are surrounded by largely deformed areas.

Evolution of microstructure, texture and inhibitor along the processing route for grain-oriented electrical steels using strip casting

In the present work, a regular grade GO sheet was produced successively by strip casting, hot rolling, normalizing annealing, two-stage cold rolling with intermediate annealing, primary recrystallization annealing, secondary recrystallization annealing and purification. The aim of this paper was to characterize the evolution of microstructure, texture and inhibitor along the new processing route by comprehensive utilization of optical microscopy, X-ray diffraction and transmission electron microscopy. It was found that a fine microstructure with the ferrite grain size range of 7–12μm could be obtained in the primary recrystallization annealed sheet though a very coarse microstructure was produced in the initial as-cast strip. The main finding was that the “texture memory” effect on Goss texture started on the through-thickness intermediate annealed strip after first cold rolling, which was not similar to the “texture memory” effect on Goss texture starting on the surface layers of the hot rolled strip in the conventional production route. As a result, the origin of Goss nuclei capable of secondary recrystallization lied in the grains already presented in Goss orientation in the intermediate annealed strip after first cold rolling. Another finding was that fine and dispersive inhibitors (mainly AlN) were easy to be produced in the primary recrystallization microstructure due to the initial rapid solidification during strip casting and the subsequent rapid cooling, and the very high temperature reheating usually used before hot rolling in the conventional production route could be avoided.

The evolution of the rolling and recrystallization textures in cold-rolled Al containing high Mn austenitic steels

High Mn TWIP steel is regarded as a promising material for the next generation automobile steel because of its high strength and good ductility. Most of the rolling and recrystallization texture studies of TWIP steels have been made at relatively low rolling reductions (50–60%). In this study, the rolling and recrystallization textures of 60–80% cold-rolled Fe-18% Mn-xAl-0.6% C steel with x being 0–3% have been investigated. The α fiber connecting Goss {110}<001> and brass {110}<112> orientations in the Euler space developed in the cold-rolled sheets, whose orientation density tended to increase with increasing rolling reduction and Al content. The α fiber rolling texture transformed into the recrystallization texture consisting of the main Goss component and minor brass component after annealing for 10 min at 800 °C, implying that the brass orientation transformed into the Goss orientation during recrystallization. The orientation transition was discussed in terms of the strain-energy-release-maximization theory for the recrystallization texture evolution.

Simulating effects of texture on grain boundary character distribution during grain growth

A modified Monte Carlo method has been used to simulate the impact of texture on grain boundary character distribution (GBCD) in this study. Polycrystals with random orientations and various texture intensities defined by fraction of Goss orientation initial microstructures were generated. Real grain orientations in Euler space were incorporated into our model and swap method were used to generate texture cluster to explore the effects on GBCD. It was found that the initial microstructure with texture cluster has a steadier GBCD than microstructure without texture. Distribution of grain boundary at triple junction was also analysed to evaluate materials susceptibility to crack propagation. Statistic shows that more special boundaries exist at triple junction with improved texture intensity. The significant increasing of Σ17b boundary was also found when strengthening texture intensity.

Secondary recrystallization behavior in the rolled columnar-grained Fe–Ga alloys

The secondary recrystallization behavior with temperature increasing from 900 to 1080°C was investigated in the rolled columnar-grained magnetostrictive Fe–Ga alloy sheets. The abnormal Goss grain growth occurred due to the inhibitory action of NbC in the Fe–Ga–0.1at%NbC sheets. With the temperature increasing at a rate of 0.25°C/min, the secondary recrystallization started below 950°C. In addition to the S-induced surface energy effect, sulfur annealing also introduced a large number of S-rich and Nb-rich precipitates, which retarded the grain boundary migration on the surface. The abnormal grain growth was found to be restricted inside the sheet during the sulfur annealing process when the temperature was below 1000°C, and a large amount of small island-like grains was remained on S-annealed sheets. After final Ar/H2 annealing processes, the S-rich precipitates and small island-like grains were eliminated, and sharp Goss orientation and high magnetostriction of 245ppm were obtained in the final S-annealed sheets.

Shear banding and its contribution to texture evolution in rotated Goss orientations of BCC structured materials

Due to progressive deformation, the dislocation densities in crystals are accumulated and the resistance of grains to further deformation increases. Homogeneous deformation becomes energetically less favorable, which may result for some orientations in strain localization. In-grain shear banding, a typical kind of localized deformation in metals with BCC crystal structure, has been accounted for by the geometric softening of crystals. In this study, the occurrence of shear bands in rotated Goss ({110}<110>) orientations of Fe-Si steel is predicted by crystal plasticity simulations and validated by EBSD measurements. It was observed and confirmed by crystal plasticity modeling that such shear bands exhibit stable cube orientations The orientation evolution of crystals in shear bands and its impact on annealing texture of materials are also described.

高純度3.3%Si鋼での二次再結晶発現

Possibility of the occurrence of secondary recrystallization in high purity material without containing inhibitor elements was investigated experimentally. Only in the sample with primary recrystallization annealing performed at 900°C, onset of secondary recrystallization was observed. The orientation of secondary recrystallized grains proved to be {110} <001> (Goss) orientation. It was also shown that normal grain growth was suppressed in the sample in which secondary recrystallization occurred. Narrow grain size distribution and strong texture accumulation were considered to help the stabilization of the matrix grains. Texture development during secondary recrystallization in the absence of inhibitors was discussed based on proposed growth models. It was shown from Grain Boundary Character Distribution (GBCD) analysis that the High Energy (HE) boundary model was applicable to secondary recrystallization and the Solid State Wetting (SSW) model was applicable to normal grain growth. The HE boundary was related theoretically to high mobility through high grain boundary diffusion coefficient. It was considered that reducing impurity elements exerted inherent high mobility of the HE boundary and hence led to the onset of the secondary recrystallization.

Development of microstructure and texture in strip casting grain oriented silicon steel

Abstract Grain oriented silicon steel was produced by strip casting and two-stage cold rolling processes. The development of microstructure and texture was investigated by using optical microscopy, X-ray diffraction and electron backscattered diffraction. It is shown that the microstructure and texture evolutions of strip casting grain oriented silicon steel are significantly distinct from those in the conventional processing route. The as-cast strip is composed of coarse solidification grains and characterized by pronounced 〈001〉//ND texture together with very weak Goss texture. The initial coarse microstructure enhances {111} shear bands formation during the first cold rolling and then leads to the homogeneously distributed Goss grains through the thickness of intermediate annealed sheet. After the secondary cold rolling and primary annealing, strong γ fiber texture with a peak at {111}〈112〉 dominates the primary recrystallization texture, which is beneficial to the abnormal growth of Goss grain during the subsequent high temperature annealing. Therefore, the secondary recrystallization of Goss orientation evolves completely after the high temperature annealing and the grain oriented silicon steel with a good magnetic properties ( B 8 =1.94 T, P 1.7/50 =1.3 W/kg) can be prepared.

Evolution of microstructures and texture in the surface layer of copper during burnishing process

The evolution of microstructures and texture subjected to a burnishing process in pure copper was investigated by transmission electron microscopy and electron backscattered diffraction. The grains of the top surface underwent significant refinement with a minimum grain size of ∼100 nm. The grain refinement was dominated by dislocation activities, including formation of dislocation cells, transformation of cell walls into sub-grain boundaries, development of highly disoriented sub-boundaries and generation of equiaxed grains. Shear strain induced by friction affected the strain state at the first pass of burnishing, resulting in a {001}<110> shear texture. Brass orientation developed well at the early stage of burnishing. Then, with a further increase in plastic strain, Brass orientation decreased, while the Goss orientation was observed, which mainly owing to the transformation from Brass to Goss orientation by rotation along the α-fibre. Moreover, dynamic recrystallisation occurred as the strain increased.

Effect of heating rate on mechanical property, microstructure and texture evolution of Al–Mg–Si–Cu alloy during solution treatment

The effect of heating rate on the mechanical properties, microstructure and texture of Al–Mg–Si–Cu alloy during solution treatment was investigated through tensile testing, scanning electron microscope, scanning transmission electron microscope, metallographic observation and EBSD measurement. The experimental results reveal that there are great differences in the mechanical properties, microstructures and textures after the solution treatment with two different heating rates. Compared with the alloy sheet solution treated with slow heating rate, the alloy sheet solution treated with rapid heating rate possesses weak mechanical property anisotropy and higher average r value. The equiaxed grain is the main recrystallization microstructure for the case of rapid heating rate, while the elongated grain appears in the case of slow heating rate. The texture components are also quite different in the two cases, CubeND orientation is the main texture component for the former case, while the latter one includes Cube, R, Goss, P and Brass orientations. The relationship between r value, texture components and microstructure has also been established in this paper.

Correlating r-value and through thickness texture in Al–Mg–Si alloy sheets

The r-value or Lankford constant is commonly used to evaluate the plastic anisotropy of rolled sheet. Computational methods based on crystal plasticity models have been developed to calculate the r-value profile from crystallographic texture. In aluminium alloys mid-thickness textures, either measured or calculated, are usually used as input and they are assumed to represent the entire through thickness texture. This paper aims to verify the validity of this assumption using two commercially produced cold rolled and annealed alloys, EN AW-6016 and EN AW-6061, having the typical cube dominated texture. The r-value profiles were calculated with both the full constraints Taylor and the visco-plastic self-consistent models, using either the measured mid-thickness or through thickness texture as input. Comparison with the experimentally measured r-value profile shows that due to the presence of a subtle through thickness gradient of the Goss orientation, the use of the precise thickness averaged texture is required for an accurate estimation of the r-value profile in cold rolled and annealed 6xxx aluminium alloys.

Sharp Goss orientation and large magnetostriction in the rolled columnar-grained Fe–Ga alloys

Abstract In this work, the 〈1 0 0〉 directional solidified feedstock slabs were used to produce the rolled Fe–Ga sheets, and sharp Goss orientation was developed in the 0.3 mm sheets after annealing processes. The area fraction of Goss grains in the annealed binary Fe–Ga sheets approached to 62.4% without abnormal grain growth, accompanied with a maximum magnetostriction ( λ // − λ ⊥ ) of 199 ppm. The addition of only 0.1 at% NbC notably promoted the abnormal Goss grain growth without sulfur annealing, and large single-crystal-like grains, up to several centimeters, were obtained with few island-like grains after sulfur annealing and final Ar/H 2 annealing processes. High magnetostriction ( λ // − λ ⊥ ) of 245 ppm with little deviation was achieved in the (Fe 83 Ga 17 ) 99.9 (NbC) 0.1 sheets, and a large magnetostrictive strain ( λ // ) up to 243 ppm under no pre-stress was observed with an applied magnetic field along the rolling direction.

Texture evolution and probability distribution of Goss orientation in magnetostrictive Fe–Ga alloy sheets

Texture evolution and the distribution of Goss orientation in polycrystalline Fe–Ga alloy were investigated as a series of rolling and subsequent annealing processes were used to develop highly textured rolled sheet. A dramatic change from the random nature of the as-rolled and primary recrystallized texture is observed when careful control of atmosphere and temperature during anneal leads to development of a sharp Goss orientation over up to 98 % of the surface of a sample during secondary recrystallization. In this work, grain boundary properties in local areas surrounding Goss grains are investigated and the evolution of Goss orientation is traced through the different stages of alloy processing using electron backscatter diffraction analysis. To evaluate the evolution of grains with Goss orientation, {011} grains are selected and separated from other texture components at each processing step and statistical analysis used to correlate the structural inheritance chain of Goss-oriented grains. The four processing stages considered are the alloy after hot rolling, the as-rolled alloy (i.e., after subsequent warm and cold rolling), the alloy after an initial anneal during which primary recrystallization occurs, and the alloy after final anneals in which secondary recrystallization with abnormal grain growth occurs. Analysis of Goss grain orientation probability distribution functions after primary and secondary recrystallization convincingly demonstrates that the orientation of the abnormally grown Goss texture that develops during secondary recrystallization is determined by the orientation of Goss components that develop during the primary recrystallization stage of alloy processing.

Effect of Sn on HighPermeability Grain-Oriented Silicon Steel

The effect of Sn on highpermeability grain-oriented silicon steel was studied by PHI-700 Auger electron spectroscopy (AES), JEM-2100 transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) technology. The results show that (1) the magnetic properties could be significantly increased by adding Sn; (2) the primary grain size becomes smaller with the addition of 0.19 wt% Sn and the Goss orientation crystal nucleus become more numerous as well; (3) the grain boundary segregation of Sn is still obvious at 970 °C in hightemperature annealing process; and (4) the average size of precipitates becomes smaller with the addition of 0.19 wt% Sn; meanwhile the dispersion and the inhibitor are also promoted. These conclusions are in agreement with the experimental results.

Goss Texture Evolution of Grain Oriented Silicon Steel by High-Energy X-ray Diffraction

High energy synchrotron diffraction offers great potential to study the recrystallization kinetics of metallic materials. To study the formation of Goss texture ({110}〈001〉) of grain oriented (GO) silicon steel during secondary recrystallization process, an in situ experiment using high energy X-ray diffraction was designed. The results showed that the secondary recrystallization began when the heating temperature was 1,494 K, and the grains grew rapidly above this temperature. With an increase in annealing temperature, the large grains with γ orientation [〈111〉//normal direction] formed and gradually occupied the dominant position. As the annealing temperature increased even further, the grains with Goss orientation to a very large size by devouring the γ orientation grains that formed in the early annealing stage. A single crystal with a Goss orientation was observed in the GO silicon steel when the annealing temperature was 1,540 K.

On the evolution and modelling of brass-type texture in cold-rolled twinning-induced plasticity steel

A combination of X-ray diffraction and visco-plastic self-consistent (VPSC) modelling was used to track the texture evolution in an Fe–28Mn–0.28C twinning-induced plasticity steel subjected to cold-rolling between 12% and 80% thickness reduction. Texture measurements returned the characteristic α-fibre for low stacking fault energy face-centred-cubic materials along with a weaker γ-fibre. VPSC modelling has been used to simulate real-world rolling conditions by simultaneously approximating the composite deformation pattern in heavily twinned and untwinned (or sparsely twinned) grains and empirically accounting for the usually overlooked, redundant shear effect. When the above two factors are combined with a grain–matrix interaction scheme that approaches a Sachs-type model, the evolution of the Goss and Brass orientations on the α-fibre is well captured and for the first time, the F orientation along the γ-fibre is successfully predicted.

The Relationship Between Inhibitors and Secondary Recrystallization Characteristics of High Permeability Grain-Oriented Electrical Steel

In order to understand the secondary recrystallization characteristics of high-permeability grain-oriented electrical steel, we studied microstructure, Goss orientation, onset secondary recrystallization temperature and Σ3, Σ5 and Σ9 grain boundaries during high temperature annealing. In particular, we examined the effect of different amounts of AlN inhibitors on the secondary recrystallization behavior. First, with the increase of AlN amount, the onset secondary recrystallization temperature and magnetic properties increase. Second, when the inhibitory ability is weak, the fraction of grains that have Goss±5, Goss±10, and Goss±15 keep constant before secondary recrystallization; with the increase of AlN amount, the fraction of grains that have Goss±15 keep almost constant, but the Goss±5 and Goss±10 grains increase obviously with the increase of temperature. Third, the frequency of Σ3, Σ5, Σ9 grain boundaries around Goss grains and general grains keeps almost constant with the increase of temperature before secondary recrystallization when having enough AlN inhibitors; however, when the content of AlN is very low, the frequency of Σ3, Σ5 and Σ9 grain boundaries around Goss grains will decrease to the level of that around general grains, which eventually leads to unsuccessful secondary recrystallization.

Influence of Friction on Surface Asperity Flattening Process in Cold Uniaxial Planar Compression (CUPC)

Atomic force microscope and electron back-scattering diffraction measurement methods were used to study the effects of friction on surface asperity flattening and surface texture during the uniaxial planar compression of annealed aluminum alloy. With an increase in gauged reduction, surface asperity tended to be flattened. Friction could boost the surface asperity flattening process by reducing the flow stress in deformation. The development of surface asperity features demonstrated that friction can effectively hinder the development of the Goss orientation component {011} and clearly promote the generation of brass orientation {011} orientation. Regardless of whether the sample was compressed with lubricant or not, a few S orientation component {123} formed in sample edge area.

Influence of Shear Banding on the Formation of Brass-type Textures in Polycrystalline fcc Metals with Low Stacking Fault Energy

Texture evolution in nickel, copper and α-brass that are representative of face-centered-cubic (fcc) materials with different stacking fault energy (SFE) during cold rolling was systematically investigated. X-ray diffraction, scanning electron microscopy and electron backscatter diffraction techniques were employed to characterize microstructures and local orientation distributions of specimens at different thickness reductions. Besides, Taylor and Schmid factors of the {111} slip systems and {111} twin systems for some typical orientations were utilized to explore the relationship between texture evolution and deformation microstructures. It was found that in fcc metals with low SFE at large deformations, the copper-oriented grains rotated around the crystallographic axis through the brass-R orientation to the Goss orientation, and finally toward the brass orientation. The initiation of shear banding was the dominant mechanism for the above-mentioned texture transition.