Si Alloy Sheets Research Articles

Synergistic mechanism of hetero-structured Al–Mg–Si–Cu–Zn–Fe–Mn alloys with greatly enhanced strength, ductility and formability

Al–Mg–Si alloy sheets applied in automobile industry are required to possess good formability, high strength and ductility. Herein, our results show that a heterogeneous cellular microstructure, i.e., soft domains embedded in hard domains, can be readily attained via a short-flow processing route with concomitant improvement in the strength (YS: 177–184 MPa, UTS: 317–328 MPa), elongation (25.7%–27.3 %) and formability (r‾= 0.771, Δr = 0.047) of pre-aged alloy. The distribution of recrystallization grains, texture and coupled soft/hard domains in the Al–Mg–Si–Cu–Zn–Fe–Mn alloys and the effect on mechanical properties have been investigated. Moreover, the formation and synergistic action mechanisms of coupled soft/hard domains were put forward in this work.

Annealing temperature effects on microstructure and magnetic properties of Fe-6.5wt. %Si alloy strips prepared by TSTRC process

The Fe-6.5wt.%Si alloy exhibits remarkable soft magnetic characteristics, such as high magnetic permeability, low coercivity, high resistivity, and nearly zero magnetostriction. These attributes establish it as an ideal material for low-power, low-noise electric motors and transformers. This investigation aimed to assess the impact of annealing temperature (ranging from 800 to 1200 °C for 1 h) on the microstructure, texture, and magnetic properties of a 0.15 mm thick Fe-6.5wt.%Si alloy sheet, which was obtained by subjecting the strips produced through the top side-pouring twin-roll casting (TSTRC) process to multi-pass warm rolling in the temperature range of 600 ∼ 800 °C, avoiding hot rolling. Additionally, the recrystallization mechanism of the annealed sheet at 1100 °C for 1 h was explored. The findings indicate that enhancing the annealing temperature corresponded to a reduction in magnetic induction (B8 and B50) as well as iron losses (P10/50, P10/400, and P2/1000). The annealed sheet at 1200 °C for 1 h demonstrated the most favorable magnetic properties, displaying iron losses of 0.486 W/kg, 6.895 W/kg, and 1.232 W/kg for P10/50, P10/400, and P2/1000, respectively. These results illustrate excellent overall magnetic characteristics. The coercivity (Hc) of both B8 and B50 decreased as the annealing temperature increased in the hysteresis loop measurements. Specifically, for B8, it decreased from 62.84 A/m to 24.50 A/m, and for B50, it decreased from 78.10 A/m to 35.50 A/m. The average grain size of the samples gradually increased as the annealing temperature ranged from 800 to 1200 °C. The dominant texture observed was {111}, and the volume fraction of {111} texture increased while the volume fractions of {100} and {110} textures decreased. Upon annealing at 1100 °C for 8 s, the elongated and flattened deformed structures were mainly replaced by equiaxed grains, indicating the completion of the recrystallization process. However, there was a noticeable distinction in the coarsening degree of equiaxed grains based on their orientations. The presence of λ-oriented grains was less prominent, while α-oriented and γ-oriented grains were relatively more abundant. As the annealing time increased from 8 s to 1 h, there was a decrease in the presence of λ-oriented and α-oriented grains, while the presence of γ-oriented grains significantly increased.

Study of Decomposition of Supersaturated Solid Solution upon Quenching of Al–Mg–Si Alloy Sheets at Different Cooling Regimes

Study of Decomposition of Supersaturated Solid Solution upon Quenching of Al–Mg–Si Alloy Sheets at Different Cooling Regimes

Formation mechanism of texture in ultra-thin Fe Si alloy sheet with excellent medium frequency magnetic properties fabricated by multi-stage decarburizing and cold rolling

Formation mechanism of texture in ultra-thin Fe Si alloy sheet with excellent medium frequency magnetic properties fabricated by multi-stage decarburizing and cold rolling

Thin Fe–Si–Al alloy sheet fabricated by Al gradient diffusion through PVD for excellent high-frequency magnetic properties

In recent years, research on environmentally friendly methods to reduce energy loss of high-frequency transformers has gained momentum. In this study, an Fe–Si–Al alloy sheet with excellent magnetic properties at high frequencies was fabricated by an environment-friendly method involving Al diffusion through physical vapor deposition for high-frequency transformer applications. To improve the magnetic properties of the alloy, the effects of Al diffusion patterns and frequency on the magnetic properties of the Fe–Si alloy sheet were theoretically and experimentally investigated. Up to 12-µm-thick Al was deposited via physical sputtering on a 0.2-mm Fe–Si alloy sheet, which was subsequently annealed for 10–90 min under 10−4 Torr without changing the grain size and texture or forming an intermetallic phase. At 50 Hz, the eddy current loss reached a minimum, when the Al diffusion into the surface and interior was uniform with a deviation of approximately 10 %. In contrast, the high-frequency (above 400 Hz) eddy current loss was minimized, when more than 70 % of the total Al was concentrated on the surface to a depth of 1/4 area. Tension effect occurred owing to the difference between the thermal expansion coefficients of the surface Al-diffused part and the that in the interior. This tension effect minimized the eddy current loss by reducing the domain width. The core loss of our specimen at 20 kHz (8.36 W/kg) was approximately 15 % superior to that of a commercial Si steel sheet of the same thickness. These results indicate the potential of the proposed method in high-frequency transformer eco-technology.

Effect of Homogenization Heat Treatment on Elongation Anisotropy in Cold-Rolled and Annealed Al–Si Alloy Sheets Fabricated from Vertical-Type High-Speed Twin-Roll Cast Strips

Effect of Homogenization Heat Treatment on Elongation Anisotropy in Cold-Rolled and Annealed Al–Si Alloy Sheets Fabricated from Vertical-Type High-Speed Twin-Roll Cast Strips

Gaussian process regression-based Bayesian optimization of the insulation-coating process for Fe–Si alloy sheets

High-efficiency Fe–Si alloy sheets have recently gained increasing attention in the automobile industry, and these sheets must be coated with insulation to reduce energy loss. However, it is difficult to maintain the coating without peeling and to realize high electrical insulation in the high-temperature heat treatment process during coating. In this study, using an artificial intelligence algorithm— Gaussian process regression (GPR)-assisted Bayesian optimization (BO)—we successfully developed a zirconia-based coating material for Fe–Si alloy sheets, yielding high heat resistance and high-quality surface properties. The coating material developed through the optimized process exhibits a high-quality silvery-white surface, the absence of coating damage even after heat treatment at temperatures exceeding 1100 K, and a surface current value of 600 mA or less, which is a measure of insulation. Notably, compared to the existing trial-and-error method, the number of experiments required to simultaneously achieve the target characteristics was reduced to less than 0.1% using the GPR-assisted BO, demonstrating the feasibility of the approach. This result also validates the efficiency and effectiveness of the proposed method in achieving multidimensional nonlinear optimization in the actual mass production of steel.

Ultra-thin Fe–Si alloy sheet with excellent high frequency magnetic properties fabricated by partial decarburization combined with multi-stage cold rolling

Transformers with high operating frequencies are highly advantageous owing to their compact sizes. To improve their performance, we successfully fabricated ultra-thin Fe–Si alloy sheets using a novel partial decarburization and multistage cold rolling method. The sheets comprised a high volume fraction of uniform grains under 50 μm with 〈001〉 // rolling direction (RD) texture (78%) and displayed excellent magnetic properties at 20 kHz. Importantly, it was verified that core loss could be controlled by the growth of 〈001〉 // RD grains, and grain size was affected by the sheet thickness and annealing time. The 〈001〉 // RD grains were well developed for sheet thicknesses of 0.05mm–0.07 mm; however, under 0.05 mm, Goss grain growth was hindered by the thickness of the thin sheet. Our specimen achieved a core loss (P0.5/20,000) improvement of about 20% (4.54 W/kg) and one of the highest magnetic flux densities (1.80T) compared with commercial Fe-Si alloy sheets.

Triple the ductility of as-cast Al–Si alloys by phase-selective recrystallization

Very recently, a method of phase-selective recrystallization has been proposed to significantly increase the ductility of eutectic alloys. Different from the conventional methods, such as adding modifiers and severe plastic deformation, phase-selective recrystallization is a simple way to control the microstructures with selective recrystallization of the soft phase but refining the hard phase. In this paper, we reveal the microstructure evolution in the phase-selective recrystallization treatment of Al–Si alloys. The results show that through phase-selective recrystallization, the microstructure of the eutectic Si phase with high degree of spheroidization and fine grains of the α-Al matrix can be obtained. Simultaneously, the refined hard Si particles and the soft α-Al grains brought the unusual tensile elongation of 24%, triple of that in as-cast state. Meanwhile, the ultimate tensile strength increased from 208 MPa to 291 MPa. The performance of Al–Si alloy with phase-selective recrystallization is superior to all previous treatments and can be used to produce high performance Al–Si alloy sheet with large scale.

Enhanced grain refinement and texture weakening in Al–Mg–Si alloy through a novel thermomechanical processing

A novel thermomechanical processing including solution treatment, first rolling with large deformation and overaging based on particle-stimulated nucleation of recrystallization (PSN) was proposed to obtain an Al–Mg–Si alloy sheet with fine grain structure, weak texture and high plastic strain ratio. The difference between conventional thermomechanical processing and novel thermomechanical processing with two overaging time parameters was investigated by texture and microstructure characterization and tensile tests. The results show that the finest grain structure with an average size of 17 µm, the weakest recrystallization texture with a volume fraction of 8.4 %, the highest average plastic strain ratio r of 0.69 and the lowest planar anisotropy Δr of − 0.001 were acquired by the novel thermomechanical processing with a long overaging time. In comparison with conventional thermomechanical processing, the novel thermomechanical processing can generate completely different particle distributions and tends to develop a weak texture consisting of the CubeND {001}<310>orientation. Increasing the overaging time is effective in coarsening the particles and thus refining the grain structure, weakening the texture, and improving the average r and Δr values. The genetic characteristics of texture evolution and the particle distribution determine the final recrystallization texture.

Microstructure, Texture, and Formability Control by Initial Hot‐Rolling Temperature of Al–Mg–Si Alloy Sheets for Automotive Applications

The effect of initial hot‐rolling temperature on microstructure, texture, and formability of Al–Mg–Si alloy sheets is investigated using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and tensile test. The results indicate that the textures of the sheet after hot‐rolling comprise most of Copper {112}&lt;111&gt;, Brass {011}&lt;211&gt;, and S {123}&lt;634&gt;. Initial rolling temperature affects the particles distribution before solution treatment, thereby further influencing the recrystallized microstructure and texture after T4P treatment. After T4P treatment, Cube {001}&lt;100&gt; component is the main grain orientation in the sheet with an initial rolling temperature of 530 °C. While CubeND {001}&lt;310&gt; orientation forms after other three initial rolling temperatures (450, 500, and 555 °C). However, the grain orientation distribution is more dispersed with an initial rolling temperature of 555 °C. Within the initial rolling temperature range from 530 to 555 °C, the average plastic strain ratio r value of the sheet is relatively higher. The anisotropy Δr value at an initial rolling temperature of 555 °C is the closest to zero. Therefore, the initial rolling temperature of 555 °C is the most conducive to improving the formability of the alloy sheet.

Experiments and Crystal Plasticity Simulations on Plastic Anisotropy of Naturally Aged and Annealed Al–Mg–Si Alloy Sheets

The influence of the heat treatment on the plastic anisotropy of an Al–Mg–Si sheet was investigated by experiments and crystal plasticity simulations. Uniaxial tension tests were conducted for the naturally aged (T4 temper) and annealed (O temper) Al–Mg–Si sheets. Solute atoms Mg and Si form clusters in the T4 temper sheet, while they bind to form precipitates in the O temper sheet. It is found that the in-plane variation of the R value, texture, and grain size are almost identical for both sheets. By contrast, the anisotropy of the flow stress is clearly dissimilar; the flow stress is the highest in the diagonal direction for the O temper sheet, whereas the flow stress in that direction is nearly lowest for the T4 temper sheet. Thus, the heat treatment alters the anisotropy of the flow stress. The plastic behaviors of the specimens were simulated using the dislocation density-based crystal plasticity model. The influence of the dislocation interaction matrix on the plastic anisotropy was examined. The orientation dependence of the flow stress is found to be sensitive to the interaction matrix. The flow stresses predicted by the interaction matrix determined based on the dislocation dynamic simulation agree with the experimental results for the O temper sheet. Whereas this interaction matrix does not reproduce the flow stress anisotropy for the T4 temper sheet. When the interactions among the dislocations are set to equivalent—i.e., the interaction matrix is filled with unity—the crystal plasticity simulation results in the flow stress anisotropy that is similar to the experimental trend of the T4 temper sheet. In contrast to the flow stress, the R value is insensitive to the interaction matrix, and the predicted R values agree with the experimental results for both specimens.

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Cu–Ni–Si合金板の強度と導電率に及ぼす極低温高速圧延の影響

Effect of heating rate during solution treatment on the bendability of Al–Mg–Si alloys

The bendability of Al–Mg–Si alloy sheets is a key parameter for their application as skins of automotive body panels. In the present study, the influence of heating rate on the bendability of Al-0.6Mg-1.0Si (in wt%) alloy was investigated using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The bendability of Al–Mg–Si alloy was found to be significantly dependent on the heating rate of solution treatment. After bending, the rapidly heated specimen exhibited only slight surface undulation, while the slowly heated specimen showed severe surface necking and even micro-cracks. The severe surface necking was caused by intensive shear bands formed during bending, and the micro-cracks were the results of the interaction between the intensive shear bands and coarse second phase particles. Elongated coarse grains were more likely to produce intensive shear bands, and cube-oriented grains impeded the formation of shear bands. The schematics of recrystallization and bending processes for Al-0.6 Mg-1.0 Si alloy considering two different heating rates are proposed.

Texture evolution and mechanical properties of Al–Mg–Si alloys at different intermediate annealing temperatures

Intermediate annealing treatment produces different effects on the state of particles in Al–Mg–Si alloy sheets, thereby affecting their recrystallization textures and formability. To improve the formability of the sheets, the effects of different intermediate annealing temperatures on the texture evolution and mechanical properties of these sheets for automotive applications were studied using optical microscope (OM), scanning electron microscope (SEM) and tensile tests. The results reveal that intermediate annealing temperature has a significant influence on the recrystallization textures and average plastic strain ratio (r). After solution treatment, all the alloy sheets possess similar recrystallization texture components comprising of cubeND {100} and P {011} orientations, whereas a characteristic strong cube-oriented {100} texture is observed only in the alloy annealed at a temperature of 380 °C. However, in comparison with the alloy not annealed, and the alloy annealed at 550 °C, the alloy annealed at 380 °C possesses a lower average r value. Furthermore, the relationship between textures and r value was analyzed by using the Taylor full constraints model in this study.

Microstructure and cracking behavior of hydroxide films formed on aluminum-alloy sheets prepared by steam coating

To elucidate the adhesion properties of anticorrosion hydroxide films formed on aluminum (Al)-alloy sheets prepared by the steam coating process, cracks that propagated inside the hydroxide film formed on Al–Mg–Si alloy (6061 grade) sheets were characterized. Continuous hydroxide films with different thicknesses of 0.7 μm and 1.4 μm formed at different temperatures of 180 °C and 200 °C, respectively. Microstructural characterizations revealed that these hydroxide films exhibited a dual-layer structure consisting of a polycrystalline γ-AlO(OH) layer (on the surface side) and a continuous amorphous layer (on the Al-alloy side). Bending tests caused numerous cracks inside the hydroxide films under tension and compression. On the tensile-strained surface, numerous vertical cracks penetrated through the hydroxide films, although their delamination was not observed. On the compressive-strained surface, local delamination of the upper γ-AlO(OH) layer occurred. However, cracks were not observed in the lower amorphous layer on the Al-alloy substrate deformed under compression. These results indicate that the dual-layer-structured hydroxide film prepared by steam coating exhibits remarkable adhesion to the Al-alloy substrate.

Fabrication of Fe-2.1 wt.% Si Alloy Sheets with Dominant Goss Texture Through Thickness

Macro- and micro-texture of Fe-2.1 wt.% Si alloy sheets were investigated and analyzed by X-ray diffraction and electron backscattered diffraction techniques. A Goss ({110} ) component accompanied by extremely weak γ ( //ND, normal direction) fiber is successfully formed through the sheet thickness after primary recrystallization and considerable grain growth. Goss grains mainly nucleate at shear bands in various deformed matrices with orientations spreading from //ND to //ND fibers. The formation of dominant Goss recrystallization texture through the thickness can be attributed to the suppression of the nucleation at grain boundaries of γ deformed matrices and the promotion of the nucleation at shear bands in various deformed matrices, based on optimization of the initial texture and microstructure and the applied processing parameters.

Enhanced Interfacial Reaction of Fe–Si Alloy Sheets Hot-Dipped in Zn Melt at 460°C

Enhanced Interfacial Reaction of Fe–Si Alloy Sheets Hot-Dipped in Zn Melt at 460°C

Bake-hardening Properties of Al-0.6Mg-1.2Si Alloy Sheets Fabricated by Twin Roll Casting

Bake-hardening Properties of Al-0.6Mg-1.2Si Alloy Sheets Fabricated by Twin Roll Casting

The rolling performance of Fe-6.5 wt.% Si sheets edged with stainless steel

Compared with common electrical steel, high silicon electrical steel (Fe-6.5 wt.% Si alloy) exhibits excellent soft magnetic properties and a wide application prospect in high frequency electromagnetic fields. In the process of cold rolling Fe-6.5 wt.% Si alloy, edge-crack often occurs on the sheets due to the inadequate ductility and limited formability. It was found that the Fe-6.5 wt.% Si alloy sheet edged with 304 stainless steel by laser welding show an improved rolling performance. The composite sheet could be cold rolled to a thickness of 0.07 mm without observed edge cracks. The mechanical property of the edging material should be in an appropriate window in reference to that of the Fe-6.5 wt.% Si alloy.