Texture Evolution Research Articles

Experimental characterization and crystal plasticity finite element simulation of the microstructural evolution in CVD tungsten during multi-step rolling

Atmospheric pressure chemical vapor deposition (CVD) is a promising technique for the preparation of tungsten products with high purity, high density and almost unlimited thickness. The tungsten prepared by using the CVD method (CVD-W) usually has a columnar coarse grain microstructure with strong preferred orientations. Multi-step rolling at gradually decreased operating temperatures is an effective method to lower the ductile-to-brittle transition temperature in pure tungsten. So far, the microstructural evolutions of CVD-W during the multi-step rolling processing is still unclear. In this study, the microstructure evolution and texture development of CVD-W during multi-step rolling are investigated by the coupling of electron backscattering diffraction technique and full-field crystal plasticity finite element simulations. After multi-step rolling, the sample exhibits through-thickness texture gradient. A layered structure with elongated 〈100〉 // ND and 〈111〉 // ND grains is observed in the central region and Goss orientation mainly appears in the surface region. Crystal plasticity finite element simulations show that {001}〈110〉 is a stable orientation under the plane strain compression, which is realized by the rotation of {100} grains around ND. Meanwhile, the shear flow promotes the rotation of {100} grains around TD, leading to the formation of 〈111〉 // ND orientation. 〈110〉 // ND orientation is observed near the shear bands, which is generated through the rotation of {100} grains around <100> // RD axis. The rolled CVD-W exhibits crystallographic orientation dependent recrystallization behavior, which is related to the orientation dependent distortion energy generated in the rolling processing. Our studies provide fundamental insights into the microstructure evolution and texture development of CVD-W under the multi-step rolling processing.

Effect of Laser Scan Speed on Defects and Texture Development of Pure Chromium Metal Fabricated via Powder Bed Fusion-Laser Beam.

Chromium (Cr) metal has garnered significant attention in alloy systems owing to its exceptional properties, such as a high melting point, low density, and superior oxidation and corrosion resistance. However, its processing capabilities are hindered by its high ductile-brittle transition temperature (DBTT). Recently, powder bed fusion-laser beam for metals (PBF-LB/M) has emerged as a promising technique, offering the fabrication of net shapes and precise control over crystallographic texture. Nevertheless, research investigating the mechanism underlying crystallographic texture development in pure Cr via PBF-LB/M still needs to be conducted. This study explored the impact of scan speed on relative density and crystallographic texture. At the optimal scan speed, an increase in grain size attributed to epitaxial growth was observed, resulting in the formation of a <100> cubic texture. Consequently, a reduction in high-angle grain boundaries (HAGB) was achieved, suppressing defects such as cracks and enhancing relative density up to 98.1%. Furthermore, with increasing densification, Vickers hardness also exhibited a corresponding increase. These findings underscore the efficacy of PBF-LB/M for processing metals with high DBTT properties.

Mechanisms for dynamic recrystallization in a β-quenched Zr-1Nb-1Sn-0.1Fe alloy during hot compression

In this paper, uniaxial hot compression tests of β-quenched Zr-1Nb-1Sn-0.1Fe alloy under a strain of 0.91 were conducted at various temperatures ranging from 600 °C to 750 °C. The microstructure, texture evolution, deformation mode and dynamic recrystallization (DRX) mechanism were investigated using electron backscatter diffraction (EBSD). The results of the In-Grain Misorientation Axis (IGMA) method showed that the prismatic <a> was the dominant deformation mode when the temperature was 600 °C. The prismatic <a> and pyramidal <a + c> were the dominant deformation modes during hot compression between 650 and 750 °C. To study the mechanism of DRX, the geometrically necessary dislocation (GND) density, grain orientation spread (GOS) and grain reference orientation deviation (GROD) maps were calculated. The results showed that both discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) coexisted during hot compression. When deformed at 600 °C, the recrystallization mechanism was mainly DDRX, while it was mainly CDRX above 600 °C. The change in the DRX mechanism can be attributed to the activation fraction of different slip systems and the resulting development of misorientation.

Evolution of microstructure and texture and their influence on the strength of an accumulative roll bonded (ARBed) Al-Sc-Zr-Er-Ti alloy

Accumulative roll bonding (ARB) is an effective approach to improve the strength of metal sheets. This work studied the evolution of microstructure and texture and their influence on the strength of an ARBed Al-Sc-Zr-Er-Ti alloy, produced by multi-microalloying Sc, Zr, Er, and Ti into pure Al. A high-quality interface and a fine microstructure with an average grain size of ∼0.6 μm were achieved as by the ARB process. The Dillamore {4411} <11118> and the Copper {112} <111> components were sharpened in final texture as is common in ARB. However, after the 5th cycle, there was a new texture component along the α-fiber, at (φ1, Φ, φ2) ≡ (60°, 45°, 0°) in Euler space. The yield strength (YS) and tensile strength (UTS) increased with increasing the number of ARB cycles. The 7th ARBed Al-Sc-Zr-Er-Ti alloy had increased YS by 45% and UTS by 57%, respectively, compared to the initial cold rolled sheet. Strengthening was mainly attributed to dislocation strengthening, grain refinement strengthening and precipitation strengthening. There was little texture strengthening because of a strengthening and softening alternation with the change of ARB cycle.

Effect of annealing temperature on the evolution of microstructure, texture, and mechanical properties of hot-rolled 12Cr-ODS steel

To achieve high thermal efficiency, today's nuclear reactor structures are exposed to higher temperatures and pressures, which requires the use of high-strength steels with specific properties, such as ODS steels. There is a need to clarify the evolution of the microstructure and properties of steels at elevated temperatures. This study systematically investigates the evolution of microstructure, texture, and mechanical property variations of 12Cr-ODS steels after hot-rolling and subsequent annealing at 1000 °C and 1200 °C. The investigation utilizes optical microscopy, electron backscatter diffraction technique, and mechanical property measurements. The microstructure of hot-rolled samples shows a layered alternating distribution, which is distinguished by a notable presence of the α-fiber texture. Following annealing at 1000 °C, the martensite grains are smaller with a reduced hardness, while maintaining a strong α-fiber texture. After annealing at 1200 °C, there is a rapid increase in the growth of martensite grains, a significant rise in hardness, a reduction in the α-fiber texture characteristics, and an improvement in the γ-fiber texture characteristics. Moreover, the maximum intensity of the α-fiber texture diminishes as the annealing temperature increases. The mechanical properties of the samples deteriorated after annealing at 1200 °C, which can be attributed to the coarse martensite grains and the texture components containing the {001} cleavage plane dominating the occurrence of brittle cleavage fracture. The 0.1Y sample after annealing at 1000 °C exhibits an excellent combination of strength (1458 MPa) and ductility (20.3%), which is owing to the unique heterogeneous grain structure and the evolution of favorable texture.

Mechanical responses and deformation mechanisms in the AZ31 magnesium alloy during cyclic bending

Cyclic loading behavior, such as cyclic bending, is unavoidably involved in various forming processes and the service of end products. Understanding the mechanical behavior of magnesium (Mg) alloys under cyclic bending is essential for promoting their application. Despite existing research, the microscopic mechanisms at play during cyclic bending, specifically the slip and twinning-de-twinning (TDT), warrant further exploration, which is the innovative focus of our study. To address this need, cyclic bending tests were performed on an extruded AZ31 Mg plate with the in-situ digital-image-correlation (DIC) technology. And the texture evolution was determined through electro backscattered diffraction (EBSD) measurements. Concurrently, the crystal-plasticity-based bending-specific approach, EVPSC-BEND, incorporating the TDT scheme, is utilized to interpret the mechanisms involved in cyclic bending. The impact at the macroscopic level is manifested in asymmetric cyclic moment-curvature curves, stress-strain distribution, and shifting of the neutral layer. The developed textures at different regions of the beam and the twin volume fraction distribution further directly illustrate twinning-de-twinning behaviors. Particularly, the upper and lower halves of the beam experience very distinct cyclic behaviors simultaneously. The upper half experiences a twinning, detwinning, and twinning cycle, while the lower half experiences a twin-free, twinning, and detwinning cycle. Additionally, through modeling the cyclic bending with different initial textures, the strong texture dependence has been revealed. The behaviors of magnesium alloy beam under cyclic bending discovered in this work can shed light on the application of Mg alloys, such as forming processes and service of end product.

Crystallographic texture evolution during friction stir processing of AA7075 alloy

This study investigates the effects of heat input on the crystallographic texture evolution during friction stir processing of AA7075 alloys. Three different heat input levels were applied to develop friction stir-modified regions. Electron backscattered diffraction (EBSD) was utilized to measure the micro-texture in the as-received base metal and friction stir processed (FSPed) stir zones. In particular, inverse pole figure (IPF) maps, pole figures, and orientation distribution functions were employed to compare the micro-textures of different processed regions. The results indicate that as the heat input decreases, the average microhardness of the nugget zone declines, accompanied by an increase in the size of recrystallized grains. The base metal AA7075 exhibits a predominantly rotated cube texture ({001} <110>). After friction stir processing, the stir zone transitions to a rotated cube texture with decreased intensities and the presence of copper texture ({112} <111>). Notably, as the heat input increases, the rotated cube texture transforms into a copper texture.

Crystallographic texture evolution in hot-press sintered tungsten heavy alloy with the effect of niobium (Nb) addition

This study examines the impact of niobium on the crystallographic texture evolution and grain boundary distribution of hot press sintered tungsten heavy alloy (W-4.9Ni-2.1Cu). EBSD analysis was used to examine the evolution of crystallographic texture and grain boundary character distribution in sintered compacts. The important findings of this study depict that cubic texture component {001} <111> were evolved in niobium unalloyed compacts due to the solidification of atoms aligned in a specified preferred orientation. Besides, it reveals the weakness in the cubic texture in niobium alloyed compacts due to the recrystallization followed by sub structural recovery occurrence during sintering. In addition, an increase in CSL fraction in niobium alloyed compacts illustrates the dominance of surface diffusion during sintering caused by the grain refinement attributed from the niobium enrichment at the tungsten-binder interface. Metallographic studies showed that the niobium concentration increment in WHAs has concomitant effect with sintered compacts' properties. A W-4.9Ni-2.1Cu-1 Nb alloy achieved the highest values for micro-hardness (432 HV0.5), electrical conductivity (23.74 % of IACS), and relative density (99.90 %).

Texture evolution and stress formation behaviour during tensile deformation using crystal plasticity finite element method

In this work, a three-dimensional crystal plasticity (CP) model was constructed to study the texture evolution behaviour and stress distribution of AA2024 alloy under uniaxial tensile conditions. After parameter calibration, the accuracy of simulated stress–strain curve reached 98.82%, and with good convergence. It was found that the {111} plane dots of Brass in (111) pole figure predominantly prolong at an angle of approximately 35.8° with respect to the RD, while those of Copper, S, Goss and Cube scatter towards almost all directions by the way in a circular augmentation. Moreover, it was revealed that Brass orientation is more conducive to alleviating stress during deformation process, while Copper is the least effective. The situations for Cube and Goss orientations are similar.

Synergistic Improvement of Antibacterial and Osteogenic Differentiation of Thermomechanically Processed Mg-Zr-Sr-Ce Alloy: Insights into the Role of Precipitate Evolution Supported by AIMD Simulation Study.

In the present study, we have discussed the influence of forging temperature (623 K (FT623), 723 K (FT723) and 823 K (FT823)) on microstructure and texture evolution and its implication on mechanical behavior, in vitro-in vivo biocorrosion, antibacterial response, and cytocompatibility of microalloyed Mg-Zr-Sr-Ce alloy. Phase analysis, SEM, and TEM characterization confirm the presence of Mg12Ce precipitate, and its stability was further validated by performing ab initio molecular dynamic simulation study. FT723 exhibits strengthened basal texture, higher fraction of second phases, and particle-stimulated nucleation-assisted DRX grains compared to other two specimens, resulting in superior strength with comparable ductility. FT723 also exhibits superior corrosion resistance mainly due to the strengthened basal texture and lower dislocation density. All the specimens exhibit excellent antibacterial behavior with Gram-negative E. coli, Gram-positive Staphylococcus aureus, and Pseudomonas aeruginosa bacteria. 100% reduction of bacterial growth is observed within 24 h of culture of the specimens. Cytocompatibility was determined by challenging specimen extracts with the MC3T3-E1 cell lines. FT723 specimen exhibits the highest cell proliferation and alkaline phosphatase activity (ALP) because of its superior corrosion resistance. The ability of the specimens to be used in orthopedic implant application was evaluated by in vivo study in rabbit femur. Neither tissue-related infection nor the detrimental effect surrounding the implant was confirmed from histological analysis. Significant higher bone regeneration surrounding the FT723 specimen was observed in SEM analysis and fluorochrome labeling. After 60 days, the FT723 specimen exhibits the highest bone formation, suggesting it is a suitable candidate for orthopedic implant application.

On twinning and shear banding in copper single crystals with rolling texture orientations plane strain compressed at high strain rate

Crystal lattice rotations developed in copper single crystals with (110)[1–1–2](Br), (110)[001](G), (112)[11–1](C), and S (346)[63–5](S) orientations have been examined to assess the role of an impact loading on twinning, deformation banding and shear banding. The single-crystalline specimens were channel-die compressed to logarithmic strains of 0.9 with a strain rate of 4.7 × 105 s−1. The microstructures were characterised using scanning (SEM) and transmission (TEM) electron microscope, whereas electron backscattered diffraction (EBSD) in SEM and X-ray diffraction have been applied to evaluate the texture evolution. The results showed that a very high strain rate promoted the formation of deformation twins in all orientations. However, a strong variation in the twin density and number of twin families was observed depending on the orientation of the single crystal. In the Br- and G-oriented crystals, only single needle-shaped twins were observed, whereas in the C- and S-oriented crystals, the formation of compact clusters of deformation twins of two generations on different twinning planes was identified. SEM/EBSD measurements revealed that deformation bands were formed in the crystallites with G and Br orientations, whereas shear bands (SBs) were observed in the C- and S-oriented crystals. This study demonstrates that the rotation of twin and matrix platelets in narrow areas of SBs developed in C- and S-oriented crystallites, combined with deformation twinning in the re-oriented primary matrix platelets can result in the formation of texture components near the {110}<001> orientation. Finally, a crystallographic model of the formation of SBs in twinned structures of face-centred cubic metals deformed at high strain rates is proposed.

Development of Low Anisotropic Commercially Pure Titanium Foils by Asymmetric Rolling and Annealing

This work studies the evolution of microstructure, texture, and anisotropy of pure titanium foils by symmetric rolling (SR) and asymmetric rolling (ASR) and subsequent annealing. The as‐received material shows equiaxed alpha grains and strong transverse texture (S‐T texture), which leads to severe anisotropy. The index of plane anisotropy (IPA) of yield stress (YS) and ultimate tensile stress (UTS) of the as‐received material is 15.2% and 7.5%, respectively. With the increase of deformation, the S‐T texture is mainly transformed into a mixed texture of transverse texture (T texture) and rolling direction texture (R texture), which balances the start‐up of the slip system when loading in the rolling direction (RD) and transverse direction (TD), so that the mechanical stress along RD and TD are close to each other and the anisotropy is improved. Especially for the samples prepared by ASR and annealing, the appearance of more R texture or basal texture (B texture) at the same deformation makes them show lower anisotropy. Therefore, after the same annealing treatment, the IPA of titanium foil with a thickness of 0.2 mm prepared by ASR is the smallest, which is 6.6% and 0.03%, respectively, while the IPA prepared by SR is 10.5% and 2.5%.

Effect of heating-assisted ultrasonic surface rolling on the microstructure evolution and wear behavior of martensitic steel

In this study, a plastic deformation layer and a nano-gradient structure were prepared on the surface of high-strength martensitic steel using the Heating-Assisted Ultrasonic Surface Rolling (HUSR) technique. The microstructure, texture evolution, and wear performance of the plastic deformation layer were characterized and analyzed using techniques such as Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscopy (TEM). The influence of HUSR treatment on the friction and wear behavior of martensitic steel was discussed. The results indicate significant changes in the texture components, dislocation structures, and grain distribution in the plastic deformation layer prepared by HUSR. The predominant textures in the plastic deformation layer are Rotated Cube {001}<110>, Cube {001}<100>, F {111}<112>, and E {111}<110>. HUSR treatment induces the formation of abundant deformation twins and stacking faults (SF) on the surface of sample. This ultimately results in a 28.3 % increase in the surface hardness of the HUSR sample and the introduction of residual compressive stress of −746.2 MPa. The friction coefficient and wear volume of the HUSR sample are significantly reduced. After HUSR treatment, the martensitic steel exhibits excellent wear resistance.

Texture tailored through combination of molten pool morphology and scanning path in laser additive manufacturing of alloy 718

Texture control is vital for the performance improvement of laser additive manufacturing parts. In the current manuscript, the effect of molten pool morphology and scanning path on texture have been studied for Inconel 718 sample fabricated by directed energy deposition (DED). The molten pool formed at a pulse period of 20 ms is shallower than that formed at a pulse period of 100 ms. The V-shaped grains (<110> // BD) are generated in the overlapping area for all samples. While Z-type grains (<110> // SD) are generated in the molten pool center for the sample with bidirectional scanning path at a pulse period of 20 ms. The unique texture with V-shaped grains (<110> // BD) in the overlapping area and Z-type grains (<110> // SD) in the molten pool center was firstly observed in the current manuscript. The value of Taylor factor of Z-type grains (<110> // SD) is larger than that of V-shaped grains (<110> // BD). Meanwhile, the effect of different heat treatments on the texture evolution was analyzed. This research provides a promising approach for texture customization, which can also increase the understanding of texture evolution.

Characterizing changes in microstructures, mechanical and magnetic properties of non-oriented silicon steel due to pulsed current

In this paper, the influence of electrical pulse treatment (EPT) on the evolution of microstructure and texture and the resultant magnetic and mechanical properties of a cold rolled Nb-alloyed non-oriented silicon steel (NOSS) was investigated carefully. When the temperature rise caused by Joule heat is higher than the starting temperature of dissolution, more precipitates are dissolved in the EPT specimens than those subjected to the conventional heat treatment (CHT) at the same temperature, and higher current density resulted in Laves precipitates dissolved at lower temperature. The permeability of all the EPT and CHT specimens increase first and then decrease with the increasing temperature, and it reaches the maximum at the temperature for nearly the complete recrystallization. B50 is higher for the EPT specimen than CHT before the completion of recrystallization due to enhanced recrystallization, but lower than CHT after the completion because the athermal effect of pulsed current promotes the growth of γ-fiber grains, disfavoring the permeability. Moreover, the EPT specimen has the lower iron loss and lower yield strength than the CHT one at the same annealing temperature, because the dissolution of precipitates, recrystallization and grain growth in cold rolled matrix are all enhanced due to the athermal effect of pulsed current.

Towards a zero-waste sustainable biorefinery of Codium sp. seaweed: From bioactives application to soil enhancement materials

In the pursuit of sustainability and circularity, this study aimed to develop a multi-purpose biorefinery pipeline using extracts from the green seaweed Codium sp. and transforming its post-extracted biomass into biochars, emphasizing holistic resource utilization. Five extracts from Codium sp. were evaluated, testing their antioxidant potential, cytotoxicity, photoprotective effects, anti-inflammatory activity, and inhibitory capabilities against enzymes hyaluronidase, collagenase, and elastase.The ethyl acetate extract showed the highest values in the ORAC assay, indicating antioxidant activity. However, no relevant antioxidant activity was observed in the FRAP and DPPH assays for the other extracts. The hydroethanolic extract exhibited the best anti-enzymatic capacity, inhibiting elastase by 88% at 200 μg/mL. It also demonstrated a photoprotective effect and reduced ROS production (30%) induced by UVB exposure. The hydroethanolic and ethanol extracts significantly reduced the concentration of the tumour necrosis factor-alpha (TNF-α) in response to LPS stimulation, indicating anti-inflammatory activity.The hydroethanolic post-extracted biomass was converted into biochars using conventional slow pyrolysis, hydrothermal carbonization (HTC), and acid-mediated carbonization (AMC). The biochars contained 56–75% C and 22–30% O and the one synthesized by HTC had the highest textural development. The biochar obtained by AMC showed better performance in improving soil water retention capacity, suggesting that acid surface chemistry plays a more significant role than porosity.The Codium sp. extracts and biochars produced from the post-extracted biomass have demonstrated potential as a source of valuable bioactive compounds and biomaterials for a circular economy framework and biorefinery pipeline with wide-ranging applications.

Segregation-induced abnormal recrystallization behavior, texture evolution, and effects on mechanical properties in twin-roll casting 2060 Al-Cu-Li alloys

Twin-roll casting (TRC) faces persistent segregation challenges limiting widespread use., Leveraging a comprehensive suite of techniques—electron probe microanalyzer (EPMA), electron back-scattered diffraction (EBSD), and transmission electron microscope (TEM)—and rooted in a thermo-mechanical-solute integrative simulation, this study focus on a detailed exposition of the structural evolution of the 2060 Al-Cu-Li alloy, encompassing its segregation tendencies and textural transformations throughout its processing trajectory. High and low-stress TRC scenarios, TRC-3 and TRC-6, are explored. Empirical observations ascertained that the TRC venture, particularly in TRC-3, cultivates a pronounced segregation gradient, a direct offshoot of the stress gradient, thereby inducing textural disparities. During the homogenization phase, the TRC structure with diminished segregation (TRC-6) manifested signs of recovery and sustained recrystallization, an environment amiable to compositional homogeneity and tempering the pre-existing segregation. In the terminal state, a pioneering discovery elucidated that heightened segregation precipitated the β-fiber textural enhancement mechanism—a phenomenon that deteriorates properties due to the discrepancy in segregation-induced hardness. With astutely managed segregation, TRC-6 recorded tensile strengths and elongation values of 563 MPa and 7.1% respectively, marking an increment by 20.0% and 208.7% in comparison to TRC-3. This research offers vital insights into solute gradients, providing a new perspective on gradient materials.

Effects of intermediate aging on the microstructure, strength and texture evolution of the Cu–Cr–Zr-Hf alloys

Cu-0.4Cr-0.2Zr-0.2Hf (wt%) alloy plates were prepared by cryogenic rolling and intermediate aging process. The effects of intermediate aging and cryogenic rolling on the microstructural, mechanical and textural evolutions were studied by X-ray diffraction, electron backscatter diffraction and transmission electron microscopy. The results show that the combination of cryogenic rolling and intermediate aging resulted in the formation of high-density dislocations, nanoscale deformation twins, deformation bands, and nano-precipitates in the Cu–Cr–Zr-Hf alloys. The nano-precipitates formed during the intermediate aging effectively increase the flow stress, and promote the formation of the nano-twins. Besides, the combination process can both reduce the fraction of the remnant grains and refine the width of remnant grains, promoting the homogeneous deformation of the Cu–Cr–Zr-Hf alloys. The reduction of the remnant grains decreases the Brass component, and increases the S component. The profuse nano-twins and Brass-type shear band contribute to the increase in the Y component.

Special texture evolution behavior of strip-cast non-oriented electrical steel combined with in-situ experiment and CPFEM

The impact of shear deformation on texture evolution in strip-cast Fe-1.5%Si non-oriented electrical steel was studied combined with in-suit experiments and crystal plasticity finite element method (CPFEM). Throughout the deformation process, the texture evolution predominantly follows a traditional route: transitioning from {211}<036> and {411}<148> to {111}<112> orientation. In certain regions with specific stress conditions, orientation evolution shifts from {310}<236> to {411}<148>, {100}<021>, and finally to {100}<001> orientation. Crystal plasticity finite element (CPFE) simulation results show that the rotation of {310}<236> through {411}<148> to {100}<021> orientation, {211}<236> and {112}<110> orientations transition to {111} and {110} orientations, respectively, which is consistent with the experimental observations. Recrystallization texture mainly includes favorable λ and near-λ (<100>∥ND, normal direction) textures, with detrimental γ (<111>∥ND) texture essentially diminishing. In-situ heating experiments revealed {411}<148> as the primary recrystallization orientation, the mechanism involves both oriented nucleation and growth. In the edge region lacking stress constraints, the Schmid factor (SF) reaches up to 0.48, the (21-3)[111] slip system is preferentially activated, with shear bands appearing earlier in the same region. Indicating that when slip mechanism alone are inadequate for sustaining plastic deformation, the shear deformation becomes the favored mode of activation. {411}<148> orientation can serve as a transitional orientation for transitioning to {100} orientation, and further as an advantageous transitional orientation during the nucleation and growth of recrystallization. Due to the texture improvement, superior magnetic properties were achieved, with the average magnetic induction (B50) and iron loss (P1.5/50) being 1.77 T and 4.25 W/kg, respectively.

Microstructural and textural evolution of double stage cold rolled non-grain oriented electrical steel

Non-grain oriented electrical steels (NGOES) are typically used in electric applications with rotating magnetic fields and thus essential for the production of electric motors. The increasing number of electric vehicles results in a growing demand for electrical steel sheets used in the stacked laminations of rotor and stator components. E-mobility applications require the best possible magnetic properties for optimum performance and efficiency, especially at high frequencies. In addition, increased mechanical strength is necessary to withstand the centrifugal forces resulting from high revolution speeds. Chemical composition, microstructure and crystallographic texture strongly influence the magnetic properties, whereas the mechanical properties are mainly affected by the chemical composition and grain size. Optimizing the texture is a possible method for improving the magnetic properties without significantly compromising the mechanical strength. In this work a special processing route for the production of 3.25% Si NGOES sample material has been studied, using laboratory cold rolling and annealing facilities. Compared to the classical processing route of single stage cold rolling and annealing, this alternative method involves two cold rolling steps with an intermediate annealing treatment between the first and second rolling sequence and a final annealing treatment after the second rolling step. The samples were produced with different intermediate thicknesses, changing the amount of cold rolling deformation of each sample variation. The degree of deformation affects the recrystallization and grain growth behavior and thus the resulting microstructure and texture. The microstructural and textural evolution was investigated in the hot rolled, intermediate annealed and final annealed state using electron backscatter diffraction (EBSD). Finished samples were additionally examined using magnetic testing and tensile testing. The results indicate a correlation between the intermediate thickness and the final grain size of the steel samples. Furthermore, the highly grain size dependent mechanical strength and magnetic losses are influenced. EBSD-data were used to interpret the texture and to calculate a parameter describing the magnetic quality of the texture. The results show a strong improvement of magnetically favorable texture components along with increasing intermediate thickness, enabling significantly better polarization values in rolling direction and transversal direction. However, anisotropy of the magnetic properties increases as well due to the textural changes.