Search Results (85)

The production of AISI 304 stainless steel (a corrosion-resistant alloy prone to solidification defects from high alloy content) particularly benefits from twin-roll strip casting—a short-process green technology enabling sub-rapid solidification (the maximum cooling rate exceeds 1000 °C/s) control for high-performance steels. However, the internal phenomena within its molten pool remain exceptionally challenging to monitor. This study developed a multiscale numerical model to simulate coupled fluid flow, heat transfer, and solidification in AISI 304 stainless steel twin-roll strip casting. A quarter-symmetry 3D model captured macroscopic transport phenomena, while a slice model resolved mesoscopic solidification structure. Laboratory experiments had verified that the deviation between the predicted temperature field and the measured average value (1384.3 °C) was less than 5%, and the error between the solidification structure simulation and the electron backscatter diffraction (EBSD) data was within 5%. The flow field and flow trajectory showed obvious recirculation zones: the center area was mainly composed of large recirculation zones, and many small recirculation zones appeared at the edges. Parameter studies showed that, compared with the high superheat (110 °C), the low superheat (30 °C) increased the total solid fraction by 63% (from 8.3% to 13.6%) and increased the distance between the kiss point and the bottom of the molten pool by 154% (from 6.2 to 15.8 mm). The location of the kiss point is a key industrial indicator for assessing solidification integrity and the risk of strip fracture. In terms of mesoscopic solidification structure, low superheat promoted the formation of coarse columnar crystals (equiaxed crystals accounted for 8.9%), while high superheat promoted the formation of equiaxed nucleation (26.5%). The model can be used to assist in the setting of process parameters and process optimization for twin-roll strip casting. Full article

As an eco-efficient short-process manufacturing technique for aluminum alloys, twin-belt continuous casting and direct rolling (TBCCR) demonstrates significant production advantages. In this study, an Al-Fe-Si alloy system with different Fe-rich intermetallics (α-AlFe(Mn)Si and β-AlFe(Mn)Si) via TBCCR was developed for new energy vehicle batteries, utilizing the Computer Coupling of Phase Diagrams and Thermochemistry (CALPHAD) technique. Comprehensive microstructure and surface segregation analyses of continuous casted ingots and direct-rolled sheets revealed that the Al-Fe-Si alloy with a combined Fe + Si content of 0.7% and an optimal Fe/Si atomic ratio of 3:1 (FS31) presents optimized mechanical properties: ultimate tensile strength of 145.8 MPa, elongation to failure of 5.7%, accompanied by a cupping value of 6.64 mm. Notably, Mn addition further refined the grain structure of casting ingots and enhanced the strength of both ingots and rolled sheets. Among the experimental alloys, FS14 (optimal Fe/Si atomic ratio of 1:4) sheets displayed the least surface segregation upon Mn incorporation. Through systematic optimization, an Al-Fe-Si-Mn alloy composition (Fe + Si = 0.7%, Fe/Si = 1:4 atomic ratio, 0.8 wt.% Mn) was engineered for TBCCR processing, achieving enhanced comprehensive performance: ultimate tensile strength of 189.4 MPa, elongation to failure of 7.32%, and cupping value of 7.71 mm. This composition achieves an optimal balance between grain refinement, mechanical properties (strength–plasticity synergy), formability (cupping value), and corrosion resistance (corrosion current density). The performance optimization strategy integrates synergistic improvements in strength, ductility, and corrosion resistance, providing valuable guidance for developing high-performance aluminum alloys suitable for the TBCCR process. Full article

The twin-roll casting (TRC) process is widely used in the aluminum industry due to its cost efficiency and continuous production capability. However, maintaining consistently high surface quality remains challenging due to complex heat transfer behavior at the roll/strip interface. This study examines the critical influence of roll surface conditions, especially the formation of an Al coating layer, on solidification behavior and resulting strip quality in the TRC of an Al-5Mg alloy. Experimental results demonstrated that casting without an Al coating layer led to surface defects such as hot tears and porosity due to insufficient cooling. In contrast, strips produced with a stable Al coating layer exhibited excellent surface quality with no surface defects. Numerical simulations further indicated that a stable Al coating enhanced the interfacial heat transfer coefficient (up to 30,000 W/m²K), ensuring effective cooling and complete solidification before the strip exited the roll nip. Moreover, simulations validated the feasibility of using steel rolls in industrial applications, provided the coating layer was consistently maintained. This research highlights the significance of roll surface control in improving TRC product quality. Full article

The twin-roll casting (TRC) process has gained significant attention for aluminum sheet production due to its cost-effectiveness and high processing efficiency. However, controlling the initial grain structure of TRC strips remains challenging due to the absence of a hot rolling stage, necessitating an advanced predictive modeling approach. In this study, a cellular automaton–finite element (CA-FE) model was developed to predict the grain structure and texture of aluminum strips fabricated via TRC. Both pure Al and AA7075 alloys were cast under identical conditions using a pilot-scale horizontal twin-roll caster, and their microstructures were characterized experimentally. The developed model incorporated a Gaussian nucleation distribution function and an equivalent binary approach to account for the solidification behavior of multicomponent alloys. The CA-FE simulation results successfully reproduced the key aspects of solidification, grain structure, and texture evolution of TRC strips. The predicted temperature distribution and solid fraction evolution showed distinct differences between the alloys, with pure Al forming columnar grains and AA7075 developing a fully equiaxed structure, which closely matched the experimental findings. Additionally, texture analysis using inverse pole figures (IPFs) and pole figures (PFs) revealed a clear <001> orientation in pure Al, whereas AA7075 exhibited a random texture, both of which were well captured by the CA-FE model. The findings indicate that the developed model offers a reliable prediction of the solidification microstructure and texture evolution in TRC strips, making it a valuable tool for optimizing continuous casting processes. Full article

An evaluation method was proposed to calculate the deformation strain of a high-temperature mushy zone (HTMZ) related to twin-roll strip casting (TSC) with regard to typical 6.5 wt.% Si electrical steel (6.5 Si steel) on the basis of the crystal—plasticity theory. The viscoplasticity self-consistent (VPSC) model was applied to calculate the evolution discipline of crystallographic orientation (CRO) for the studied 6.5 Si steel processed by different deformation strains under a deformation mode of plane strain, and the deformation strain of HTMZ for the studied 6.5 Si steel related to TSC was further estimated by comparing the CRO feature achieved by theoretical calculation and experimental characterization. Results indicate that the distribution feature of CRO obtained by theoretical calculation becomes increasingly similar to those obtained through experimental characterization with the deformation strains increasing from 0 to 1.5. The ratio between the distribution intensities corresponding to R-Cube texture, the typical rolling texture of α-fiber, and the Cube texture achieved by theoretical calculation is the closest to the value obtained by experimental characterization at deformation strain of 1.4, and the deformation strain of HTMZ for the studied 6.5 Si steel involved in TSC is determined to be ~1.4. Full article

This study explores the development of Al-Mg alloy sheets manufactured through the Twin Roll Continuous Casting (TRC) technique, with the goal of enhancing their mechanical properties via thermomechanical processing. TRC is a cost-effective and efficient method for producing thin sheets directly from molten metal, and this work focuses on the deep drawability of AA5182, AA5754, and AA5052 alloys, widely used in automotive, packaging, and aerospace applications. Improving deep drawability is crucial for meeting the stringent requirements of these industries. The alloys were designed according to EN 573-3 standards, and sheet castings were carried out at both laboratory and industrial scales. Microstructure evolution was analyzed at the as-cast and final thicknesses using optical microscopy. The sheets underwent cold rolling to a thickness of 1 mm, followed by final annealing, and their mechanical properties—including yield strength, tensile strength, elongation, and anisotropy—were evaluated. The deep drawability of the sheets was assessed using Erichsen cupping tests and earing mechanisms. To further understand failure mechanisms, fracture surface morphologies were examined using scanning electron microscopy (SEM), while energy-dispersive X-ray spectroscopy (EDS) was performed to analyze inclusions on fractured surfaces. The findings highlight the effectiveness of the TRC technique in producing high-performance Al-Mg sheets with mechanical properties comparable to or exceeding those of conventionally processed sheets. This study provides valuable insights into the optimization of alloy design and manufacturing methods, laying the groundwork for future advancements in TRC technology. Full article

Standard AA5083 (ZSE000), AA5083 modified with 0.3 wt.% Zr and 0.3wt.% Sc (ZSE330) and AA5083 modified with 0.3 wt.% Zr, 0.2wt.% Sc and 0.1wt.%Er(ZSE321) sheets were fabricated through a short process (including a simulated twin-belt continuous casting, subsequent direct rolling, intermediate annealing, cold rolling and stress-relief annealing) to systematically investigate the influence of partially substituting Er for Sc on the microstructure, mechanical properties and corrosion resistance of short-processed Al-4.7Mg-0.6Mn-0.3Zr-0.3Sc sheets. The results show that ZSE321 presents the optimal tensile properties (UTS: 541 MPa; 0.2%PS: 469 MPa and EF:7.7%) among the three experimental sheets. This is attributed to significant grain refinement, the inhibition of the recrystallization and promotion on the precipitation of Al₃(Sc, Zr, Er) nanoparticles. Furthermore, the corrosion properties of the experimental sheets were also explored in this study, and the short-processed ZSE321 sheet presents the optimum corrosion resistance. Full article

Roll-cast strips are usually cold-rolled and annealed before forming. The elongation of these strips is known to be different between the casting and lateral directions after thinning by cold rolling. Whether cold rolling is the main factor determining the anisotropy of the elongation is not clear. Likewise, it is not clear whether the elongation anisotropy can be reduced by conventional cold rolling. Roll-cast strips have centerline segregation, forming a so-called band area. The relationship between the anisotropy of the elongation and these defects is not clear. A strip cast using an unequal-diameter twin-roll caster also has a band area but a strip cast using a single-roll caster equipped with a scraper has no centerline segregation or band area. Strips made this way were cold-rolled in the casting and lateral directions, and tensile testing was conducted on the cold-rolled and annealed strips. In this study, the ability of conventional cold rolling and one-time annealing to reduce the elongation anisotropy of a cast strip was clarified. Moreover, the influence of the band area and Fe impurities on the elongation anisotropy was determined. Full article

One advantage of twin-roll casting for aluminum alloys is that hot rolling can be omitted, thus shortening the process. The effect of inline hot rolling on the anisotropy of the mechanical properties, especially the elongation, of the roll-cast strip has not been investigated. In a high-speed twin-roll caster, inline hot rolling forms the metal shape before the temperature of the cast strip decreases below the temperature needed for hot rolling. In this study, inline hot rolling of Al-5%Mg strips cast using an unequal diameter twin-roll caster was performed to validate the technique and evaluate its ability to reduce surface cracking and improve the elongation anisotropy. A rolling speed of 30 m/min was used, and the effects of temperature and thickness reduction during inline hot rolling on the surface and mechanical properties were investigated. Inline hot rolling was found to effectively reduce the formation of surface cracks and the anisotropy of the mechanical properties. Full article

Twin-roll casting is a technology for the production of thin strips directly from liquid metal by combining continuous casting with hot rolling in a single step. The thermo-mechanical cyclic interaction with the solidifying strip causes fatigue crack formation at the outer surface of the rolls. A 2D FEM model with Eulerian boundary conditions and the interference fit load on the rolls was defined. The influence of the roll–strip thermal contact, the inlet temperature of the liquid aluminum, the efficiency of the water cooling and the production rate on the fatigue damage of the rolls was analyzed with a parametric study. The maximum temperature of the rolls, the maximum contact pressure, the accumulated plastic strain and the equivalent strain computed (considering a multiaxial out-of-phase fatigue criterion) were considered to investigate the thermo-mechanical fatigue load on the rolls. The results showed that, in the considered range, the most influential parameters on the fatigue mechanism are the heat contact conductance coefficient, which dominates the thermo-mechanical load, and the tangential velocity of the rolls, which contributes to the thermal field and determines the roll–strip mechanical contact interaction. Full article

Twin-roll strip casting (TRSC) technology has unique advantages in the production of non-oriented electrical steel. However, the hot deformation behavior of high-grade electrical steel produced by TRSC has hardly been reported. This work systematically studied the hot deformation behavior of free-Al 2.43 wt.% Si electrical steel strip produced by twin-roll strip casting. During the simulated hot rolling test, deformation reduction was set as 30%, and the ranges of deformation temperature and strain rate were 750~950 °C and 0.01~5 s⁻¹, respectively. The obtained true stress–strain curves show that the peak true stress decreased with an increase in the deformation temperature and with a decrease in the strain rate. Then, the effect of hot deformation parameters on microstructure and texture was analyzed using optical microstructure observation, X-ray diffraction, and electron backscattered diffraction examination. In addition, based on the obtained true stress–strain curves of the strip cast during hot deformation, the constitutive equation for the studied silicon steel strip was established, from which it can be found that the deformation activation energy of the studied steel strip is 83.367 kJ/mol. Finally, the kinetics model of dynamic recrystallization for predicting the recrystallization volume percent was established and was verified by a hot rolling experiment conducted on a rolling mill. Full article

We herein suggest a metallurgical method using pure aluminum with no freezing temperature range to derive appropriate roll/melt interfacial heat transfer coefficients in simulation of twin-roll casting process. This method is inspired by the concept that the position of the kiss points where two solidifying shells encounter and the roll nip coincides under the condition where the roll load becomes zero as the roll rotation speed decreases. The conditions where the roll load becomes zero under various melt supply temperature conditions in the actual TRC process are found experimentally. These conditions are then applied to simulation models to derive heat transfer coefficient values. When comparing these values with those derived previously from the empirical relation for roll rotation speed and heat transfer coefficient, the conclusion is drawn that the deviation was reasonably low, around 10%. Full article

In this work, the microstructure and texture of Mg-1.0Al-xZn-0.2Mn-0.5Ca (wt.%, x = 0, 1) alloys, which were produced via conventional casting or twin roll casting (TRC), were investigated, and their relation to the mechanical properties of the sheets at the final gage was analyzed. In the Zn-containing AZMX1100 alloy sheets, the amount and size of the secondary phases were significantly reduced, in comparison to the Zn-free AMX100 alloy sheet. The TRC sheet shows a smaller grain structure and fine secondary phases in comparison to the sheets produced via the conventional casting process. The texture of the AMX100 sheet is characterized by the basal poles tilted in the sheet rolling direction (RD). In the AZMX1100 sheets, the texture with the tilted basal poles towards the RD and transverse direction (TD) was developed after recrystallization annealing, while the tilting angle of the basal pole in the TD is larger than in the RD. There is no significant difference in the texture between the sheets produced by the casting and TRC process. The highest yield strength was obtained in the AZMX1100 sheet produced by the TRC process, and all examined sheets showed the mechanical anisotropy in accordance with their textures. Full article

The as-cast (Fe50Mn30Co10Cr10)97C2Mo1 HEA (high entropy alloy) was prepared and cold-rolled at 70%. Subsequently, annealing heat treatment at different temperatures (900 °C, 950 °C, 1000 °C) was carried out. The microstructure evolution and mechanical properties of the HEA were systematically investigated. The results showed that the HEA annealed at 900 °C and 950 °C exhibited uneven grain size and rich σ precipitation phase at grain boundaries. The grains began to grow and complete recrystallization, and no σ phases were observed in HEA annealed at 1000 °C, which resulted in a higher tensile strength of ~885 MPa and elongation of ~68% compared with other annealed HEAs. The higher volume fraction of annealing twins with 60°<111> orientation was produced in HEA annealed at 1000 °C, which enhanced the tensile strength and plasticity via the Twinning-induced plasticity (TWIP) mechanism. Full article

A homogenization of billets from Al-Cu-Li-Mg-Sc-Zr alloys should be accomplished at high annealing temperatures exceeding 500 °C. This type of aluminum alloy is susceptible to the depletion of surface layers from Li. Therefore, choosing a suitable homogenization temperature and duration is a crucial step in assuring a homogeneous distribution of alloying elements and optimal exploitation of the potential of the alloy. In situ heating in an electron microscope was performed on a twin-roll-cast Al-Cu-Li-Mg-Sc-Zr alloy to understand the peculiarities of the homogenization process. Four types of primary phase particles rich in Cu, Li, Mg, and Fe were identified in the as-cast material. They appear as coarse particles at the boundaries of eutectic cells. Their partial dissolution occurs at temperatures above 450 °C. They are almost fully dissolved at 550 °C, except for complex phases containing Fe and Cu. Small dimensions of eutectic cells in the range of 10 µm assure a homogeneous distribution of the main alloying elements within the matrix after 20 min of annealing at 530 °C. Direct comparison with the same material prepared by mold casting indicates that such short annealing times result in the dissolution of the main primary phase particles but do not assure a homogeneous distribution of the alloying elements in the whole volume of the specimen. Full article