ND Texture Research Articles

Fabrication and properties of strip casting 4.5 wt% Si steel thin sheet

Three 4.5wt% Si steel thin sheets with different thicknesses were efficiently fabricated by twin-roll strip casting, warm rolling and cold rolling followed by final annealing. A comprehensive investigation from the workability of the as-cast strip to the magnetic property of the produces was performed to illustrate the superiority of the new materials. The results show that the as-cast strip, which has a much lower Vickers hardness than that of the 6.5wt% Si steel, is suitable for rolling processing. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirm that no ordering phase exists in the as-cast strip. The cold-rolled thin sheets exhibit good surface quality without edge cracks. Furthermore, all the three 4.5wt% Si steel thin sheets possess relative strong <100>//ND texture and present high magnetic inductions and low iron losses after finial annealing.

Improvement of Surface Ridging Resistance of an Ultra-purified Ferritic Stainless Steel by Optimizing Hot Rolling Condition

The effects of the finisher entry temperatures (FETs) on the surface ridging behavior for an ultra-purified 21%Cr ferritic stainless steel have been investigated. The results indicate that decreasing the FET facilitates the formation of in-grain shear bands in the hot rolled slab. The in-grain shear bands supplied recrystallization nucleation sites in grains during subsequent annealing through coalescence of subgrains, which is beneficial to refine the microstructures and intensify the {111}//ND textures. This effect will evolve to the final cold rolled and annealed sheet. The micro-texture analysis indicates that the formation of grain colony in the final sheet is weakened by decreasing the FET. Then, the surface ridging resistance of FSS is enhanced due to the optimizing of micro-texture distribution.

Evolution of Texture and Magnetic Property in Nd–Pr–Fe–B-Based Nanocomposite Magnets With Plastic Deformation

Nanocomposite magnets consisting of various nanoscale hard and soft phases are potentially the next generation permanent magnets. Textured microstructure of hard phases is one of the necessary conditions for the predicted high magnetic energy product [1]. Hot deformation is an effective method to produce conventional anisotropic Nd 2 Fe 14 B magnets [2], in which the Nd-rich phase plays an important role for texture fomation. However, it turns out to be a challenge to apply this method to produce Nd-lean nanocomposite magnets due to the absence of Nd-rich phase [3]. In this work, a height reduction rate up to 90% was carried out in order to investigate the evolution of texture and magnetic property with plastic deformation in NdPrFeB based nanocomposite magnets. It shows that the degree of deformation is a key factor for texture formation in hot-deformed (HD) rare earth-lean nanocomposite magnets.

Texture Evolution of a Non-oriented Electrical Steel Cold Rolled at Directions Different from the Hot Rolling Direction

With the objective of optimizing the crystallographic texture of non-oriented electrical steel, i.e., reducing the 〈111〉//ND and 〈110〉//RD fibers and promoting the 〈001〉//ND texture, a new rolling scheme was proposed and tested, in which the cold rolling direction (CRD) was intentionally inclined at an angle to the hot rolling direction (HRD) in order to change the orientation flow paths during cold rolling and alter the final texture of the annealed sheets. A non-oriented electrical steel containing 0.88 wt pct Si was hot rolled using conventional routes and annealed, and a number of rectangular plates were cut from the hot band with the longitudinal directions inclined at various angles, i.e., 0, 15, 30, 45, 60, 75, and 90 deg, to the HRD. These plates were then cold rolled along the longitudinal directions with a thickness reduction of 72 pct. The cold-rolled samples were annealed, temper rolled and annealed again (final annealing). The texture evolution during hot rolling, hot band annealing, cold rolling, and final annealing was characterized by electron backscatter diffraction and X-ray diffraction techniques. By changing the CRD with respect to the HRD, the initial texture and the orientation flow paths were altered, which resulted in apparent differences in the textures as compared to conventional cold rolling. After temper rolling and final annealing, the recrystallization textures consisted of mainly a 〈001〉//ND fiber and there was almost no 〈111〉//ND fiber. The sample cold rolled at an angle of 60 deg to the HRD had the strongest texture (intensity almost 2× of conventional rolling) with a maximum at the cube {001}〈100〉 orientation—a magnetically favorable orientation for non-oriented electrical steels.

Microstructure, texture evolution and magnetic properties of strip-casting non-oriented 6.5 wt.% Si electrical steel doped with cerium

A 0.3mm thick non-oriented 6.5wt.% Si electrical steel sheet doped with cerium is produced by twin-roll strip casting, hot rolling, warm rolling and annealing. A detailed study of the cerium precipitates in the as-cast strip, microstructure and texture evolution at different processing stages is carried out by electron probe micro-analysis, optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. Grain interior distributing precipitates identified as Ce-oxides, Ce-oxysulfides and Ce-phosphides, and boundary distributing Ce-oxides and Ce-phosphides are observed in the as-cast strip. The initial as-cast strip is characterized by a much finer solidification microstructure and dominated by obvious <001>//ND texture through the strip thickness. After hot and warm rolling, inhomogeneous microstructure containing large amounts of in-grain shear bands is characterized by mixed <110>//RD and <111>//ND textures. The texture of the annealed sheet with a relatively large average grain size is far more optimized by the domination of the beneficial cube, rotated cube, {001}<120> to {001}<130> and Goss texture components, and the elimination of the detrimental γ-fiber texture, leading to a superior magnetic induction and improved iron loss.

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.

Microstructural and mechanical factors influencing high pH stress corrosion cracking susceptibility of low carbon line pipe steel

Several adjacent gas pipe sections were obtained from the field. These pipe sections had nominally identical manufacturing, construction, coating and operational conditions. Some sections were unaffected by stress corrosion cracking (SCC), whereas surrounding sections were affected by SCC. Slight differences in mechanical and microstructural properties were found between the two types of section. Residual stress/strain and hardness close to the outer surface of the pipes and high angle boundary fraction values were lower for the non-cracked pipe sections. Predominant 〈110〉//ND texture was also found at the outer surface of the non-cracked pipe sections. These characteristics lead to a lower crack growth rate in laboratory SCC experiments. These features being mainly a result of the line pipe steel manufacturing operations, appropriate metallurgical processes leading to low residual stress (6.2%YS), relatively low fraction of high angle boundaries (about 0.75) and predominant {110}〈110〉 texture in the material (or in the near surface) are expected to greatly improve the stress corrosion cracking resistance of line pipe steels on the field.

Effects of warm temper rolling on microstructure, texture and magnetic properties of strip-casting 6.5 wt% Si electrical steel

6.5wt% Si electrical steel thin sheets were produced by a processing route including strip casting, hot rolling, warm rolling, intermediate annealing, warm temper rolling and final annealing, in which the warm temper rolling reduction varied from 2.7% to 14.4%. A detailed study of the microstructural and textural evolutions through the whole processing route was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The findings revealed that the final recrystallization microstructure, texture and magnetic properties relied heavily on the warm temper rolling reduction. As the warm temper rolling reduction increased from 2.7% to 14.4%, the finally recrystallized microstructures were more homogeneous and the average grain size was decreased. At the warm temper rolling reduction lower than 7.0%, the occurrence of the exaggeratedly large annealing grains which dominated the whole sheet thickness resulted in strong 〈001〉//ND fiber, parallel α-fiber, 〈111〉//ND fiber and many other strong hard-magnetization texture components. By contrast, at the warm temper rolling reduction higher than 7.0%, the recrystallization textures were characterized by weak 〈001〉//ND fiber, parallel α-fiber, 〈111〉//ND texture, together with fewer and weak hard-magnetization texture components. The mechanism responsible for the finally microstructural and textural changes was explained by strain induced boundary migration. As warm temper rolling reduction increased, the magnetic properties at high frequency were gradually improved due to smaller grain sizes and more desirable textures. The highest magnetic inductions of 1.383T (B8), 1.484T (B25) and 1.571T (B50) in combination with the lowest iron losses at high frequencies of 19.11W/Kg (W10/400) and 3.824W/Kg (W2/1000) were obtained at 14.4% warm temper rolling reduction under the applied condition.

Characterization of microstructure, texture and magnetic properties in twin-roll casting high silicon non-oriented electrical steel

An Fe-6.5wt.% Si-0.3wt.% Al as-cast sheet was produced by twin-roll strip casting process, then treated with hot rolling, warm rolling and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy, X-ray diffraction and electron backscattered diffraction analysis. The initial as-cast strip showed strong columnar grains and pronounced <001>//ND texture. The hot rolled & warm rolled sheets were characterized by large amounts of shear bands distributed through the thickness together with strong <110>//RD texture and weak <111>//ND texture. After annealing, detrimental <111>//ND texture almost disappeared while beneficial {001}<210>, {001}<010>, {115}<5 −10 1> and {410} <001> recrystallization textures were formed, thus the magnetic induction of the annealed sheet was significantly improved. The recrystallization texture in the present study could be explained by preferred nucleation and grain growth mechanism.

Precipitation Behavior and Textural Evolution of Cold-Rolled High Strength Deep Drawing Dual-Phase Steels

Low-carbon Cr-Mo micro-alloyed deep drawing dual-phase steels were designed in laboratory. As the microstructure and texture evolution in hot-rolled strips and annealed sheets were investigated using SEM, TEM and XRD technologies, the attribution of solute Mo and MoC particles to DP sheets' drawing capacity was investigated. The precipitation thermodynamics were also calculated by Thermo-calc software. Results show that the precipitates in hot-rolled strips mainly are MoC, AlN and MnS, and with the increase of Mo-addition, finer and denser MoC particles precipitated in matrix and along grain boundaries of ferrite more easily. Weak textures are shown in the hot-rolled strips, and {112}<110> and {223}<110> components tend to be stable in subsequent cold rolling process. During annealing, on one hand, the development of <111> // ND texture is suppressed because finer MoC particles prevent the grain boundary migration. On the other hand, unfavorable texture {001}<110> significantly reduces with Mo increasing, which is attributed to that part of solution C in matrix has been fixed during recrystallization. In addition, the addition of Mo can enhance hardenability strongly and MoC easily re-dissolve at high temperature, which is favor to form martensite in dual-phase steel.

Microstructure and Mechanical Property in Thickness Direction of a Deoxidized Low-Phosphorous Copper Sheet Processed by Two-Pass Differential Speed Rolling

A two-pass differential speed rolling(DSR) was applied to a deoxidized low-phosphorous copper alloy sheet in order to form a homogeneous microstructure. Copper alloy with a thickness of 3 mm was rolled to 75 % reduction by two-pass rolling at <TEX>$150^{\circ}C$</TEX> without lubrication at a differential speed ratio of 2.0:1. In order to introduce uniform shear strain into the copper alloy sheet, the second rolling was performed after turning the sample by <TEX>$180^{\circ}$</TEX> on the transverse direction axis. Conventional rolling(CR), in which the rotating speeds of the upper roll and lower roll are identical to each other, was also performed by two-pass rolling under a total rolling reduction of 75 %, for comparison. The shear strain introduced by the conventional rolling showed positive values at positions of the upper roll side and negative values at positions of the lower roll side. However, samples processed by the DSR showed zero or positive values at all positions. {100}//ND texture was primarily developed near the surface and center of thickness for the CR, while {110}//ND texture was primarily developed for the DSR. The difference in misorientation distribution of grain boundary between the upper roll side surface and center regions was very small in the CR, while it was large in the DSR. The grain size was smallest in the upper roll side region for both the CR and the DSR. The hardness showed homogeneous distribution in the thickness direction in both CR and DSR. The average hardness was larger in CR than in DSR.

Enhancement of Grain Refinement and Formability of Cross Roll Rolled Ni-10Cr Alloy

This study evaluated the microstructure and mechanical properties enhancement of cross roll rolled Ni-10Cr alloy, comparing with conventional rolled material. Cold rolling was carried out to 90% thickness reduction and subsequently annealed at 700 °C for 30 min to obtain the fully recrystallized microstructure. Particularly, cross roll rolling was carried out at a tilted roll mill condition of 5º from the transverse direction in RD – TD plane. Application of cross roll rolling on Ni-10Cr alloy contributed to the notable grain refinement due to higher effective strain than that of conventional rolling, consequently, average grain size was refined from 135 µm in initial material to 4.2 µm in cross roll rolled material. Furthermore, //ND texture in CRR material was well developed than that of CR material, which contributed to the mechanical properties and formability enhancement.

Plastic anisotropy of electro-deposited pure α-iron with sharp crystallographic // texture in normal direction: Analysis by an explicitly dislocation-based crystal plasticity model

We present a single crystal plasticity model based on edge and screw dislocation densities for body centered cubic (bcc) crystals. In a bcc crystal screw dislocations experience high lattice friction due to their non-planar core. Hence, they have much slower velocity compared to edge dislocations. This phenomenon is modeled by accounting for the motion of screw dislocations via nucleation and expansion of kink-pairs. The model, embedded as a constitutive law into a crystal plasticity framework, is able to predict the crystallographic texture of a bcc polycrystal subjected to 70%, 80% and 90% thickness reduction. We perform a parametric study based on the velocities of edge and screw dislocations to analyze the effect on plastic anisotropy of electro-deposited pure iron with long needle-shaped grains having sharp crystallographic <111>//ND texture (ND: normal direction). The model shows a large change in the r-value (Lankford value, planar anisotropy ratio) for pure iron when the texture changes from random to <111>//ND. For different simulated cases where the crystallites have an orientation deviation of 1°, 3° and 5°, respectively, from the ideal <111>//ND axis, the simulations predict r-values between 4.0 and 7.0 which is in excellent agreement with data observed in experiments by Yoshinaga et al. (ISIJ Intern., 48 (2008) 667–670). For these specific orientations of grains, we also model the effect of long needle shaped grains via a procedure that excludes dislocation annihilation.

Microstructure and Properties of Ultrafast Annealed High Strength Steel

The grain size, recrystallization, phase transformation and mechanical properties of a cold-rolled high-strength steel (HSS) are studied after annealing with high (~140°C/s) and ultra-high (~1500°C/s) reheating rate, followed by subsequent water quenching without isothermal soaking. By monitoring the hardness and microstructure, it was shown that the increase of the reheating rate from 140°C/s to 1500°C/s causes grain refinement from 5 µm to 1 µm in diameter and the final ferrite grain size depends significantly on the reheating temperature and reheating rate. It was observed that after an extreme reheating rate of ~1500°C/s the α-γ phase transformation starts before the completion of recrystallization in the recovered matrix. The crystallographic texture of the ultrafast reheated and water-quenched high-strength steel inherits the cold-rolled deformation texture with well pronounced RD and ND texture fibres, even after the α-γ-α′ phase transformations. It was found that the ultrafast reheating results in a very fine non-equilibrium ferrite-martensite structure with an excellent ultimate tensile strength of ~1400 MPa and an acceptable elongation at fracture. The observed data are very promising from industrial application point of view and open up possibilities for further structural refinement and alternative texture control.

Effect of Coil Temperature on Microstructure and Texture Evolution of an High Strength Nb-IF Steel Sheet

Effect of coil temperature on the texture and microstructure evolution during cold rolling and annealing were investigated by OM, ODF and EBSD. The results indicate that the {223}&lt;110&gt; and {114}&lt;110&gt; textures appeared after cold rolling are inherited followed by annealing, whose intensities would be higher as the coil temperature decreased. Lower coil temperature could improve the uniformity of grain size and increase the fraction of low-angel grain boundaries as well as coincidence site lattice boundaries. And the {111}//ND texture is improved in the lower coil temperature cold and annealing steel sheet, which is beneficial for the deep-drawability.

Effect of Phosphorus Contents on Texture and Grain Boundary Character for the Annealing High Strength Ti-IF Steels

The effect of phosphorus contents on texture and grain boundaries character for the high strength Ti-IF annealed for 120sec at 810oC are researched by electron backscatter diffraction technique（EBSD）. The recrystallization texture is approximated by the γ-fiber texture whose components are {111} and {111} orientation texture. The highest volume fraction of //ND texture is almost 80% for the sample containing 0.056%P. A large amount of coincidence site lattice(CSL) grain boundaries ∑3，∑5, ∑7，∑9，∑11 and ∑13b are obtained.

Effect of Initial Texture on the Development of Microstructure and Mechanical Properties in AZ31 Magnesium Alloy after Rolling at 300°C

Mg alloys are drawing a lot of attention and have been extensively studied. The major obstacle to the practical application of the alloys is the poor formability at room temperature, originating basically from the insufficient number of slip system. Development of a proper microstructure and/or texture is one promising solution to improve the formability. In the present work, after extrusion and full annealing, rolling at 300°C with different starting textures, the microstructures, texture developments and tensile properties of AZ31 Mg alloys are studied. After full annealing strong ∥ED fiber texture and weak + ∥ED fiber texture (c-axes in the radial direction) were developed. After rolling at 300°C many twins were formed, and the strong ∥ED fiber texture changed to ∥ND texture. Yield strength, tensile strength and elongation changed obviously depending on the microstructure and textures.

Investigation on Mechanical Properties and Formability of Cross Roll Rolled Ni-10Cr Alloy

This study evaluated the microstructure and mechanical properties enhancement of cross roll rolled Ni-10Cr alloy, comparing with conventional rolled material. Cold rolling was carried out to 90% thickness reduction and subsequently annealed at 700 °C for 30 min to obtain the fully recrystallized microstructure. For annealed materials after rolling, to investigate the grain boundary characteristic distributions, electron back-scattering diffraction technique was introduced. Application of cross roll rolling on Ni-10Cr alloy contributed to the notable grain refinement, consequently, average grain size was refined from 135 μm in initial material to 4.2 μm in cross roll rolled material. These refined grain size led to an enhanced mechanical properties such as yield and tensile strengths. Furthermore, &lt;111&gt;//ND texture in CRR material was well developed than that of CR material, which contributed to the mechanical properties and formability enhancement.

Enhancement of Grain Refinement and Formability of Cross-Roll-Rolled Ni-10Cr Alloy

This study evaluated the enhancement of microstructural and mechanical properties of a cross rolled Ni-10Cr alloy, comparing with conventionally rolled material. Cold rolling was carried out to 90% thickness reduction and the specimens were subsequently annealed at for 30 min to obtain a fully recrystallized microstructure. Cross roll rolling was carried out at a tilted roll mill condition of from the transverse direction in the RD-TD plane. In order to observe the deformed microstructures of the cold rolled materials, transmission electron microscopy was employed. For annealed materials after rolling, in order to investigate the grain boundary characteristic distributions, an electron back-scattering diffraction technique was applied. Application of cold rolling to the Ni-10Cr alloy contributed to notable grain refinement, and consequently the average grain size was refined from 135 in the initial material to 9.4 and 4.2 in conventionally rolled and cross rolled materials, respectively, thus showing more significantly refined grains in the cross rolled material. This refined grain size led to enhanced mechanical properties such as yield and tensile strengths, with slightly higher values in the cross rolled material. Furthermore, the //ND texture in the CRR material was better developed compared to that of the CR material, which contributed to enhanced mechanical properties and formability.

Evolution of Textures and Microstructures in Low-Reduction Rolled and Annealed Low-Carbon Steels

A study has been made of the evolution of the microstructures and textures in three kinds of low-carbon steel sheets (MAFE, BH and IF) having well developed &lt;111&gt;//ND texture that were rolled by low reductions and annealed at 780 °C in Ar atmosphere. The steel sheets developed different microstructures and textures, even though their initial textures and thermomechanical treatments were similar. MAFE steel showed an unusual behavior that grains with high Taylor factors survived and grew very rapidly. This unusual behavior and the differences in microstructure and texture have been discussed.