Search Results (19)

Semi-continuous casting is an important method for the large-scale production of high-strength conductive copper-iron (Cu-Fe) alloys in the future. However, serious peeling defects were found on the surface of cold-rolled strips during industrial trials. Due to the multi-step complexity of the manufacturing process (from casting to final product), identifying the root cause of defect formation remains challenging. X-ray computed tomography (X-CT) was used to quantitatively characterize the pores and defects in the horizontal continuous casting Cu-Ni-Sn slab, the semi-continuous casting Cu-Fe alloy slab, and the hot-rolled slab of Cu-Fe, and the relationship between the defect characteristics and processes was analyzed. The results showed that the internal defect sphericity distribution of the Cu-Fe alloy slab after hot rolling was similar to that of the reference Cu-Ni-Sn slab. The main difference lies in the low sphericity range (<0.4). The volume of pore defects inside the Cu-Fe alloy after hot rolling was significantly larger than in the reference sample, with a 52-fold volume difference. This phenomenon may be the source of surface-peeling defects in the subsequent cold-rolling process. The occurrence of internal defects in the Cu-Fe alloy is related to both the composition characteristics and casting processes of the Cu-Fe alloy; on the other hand, it is also related to the hot-rolling process. Full article

Composite coatings on the surface of a semi-continuous cast 7005 aluminum alloy under different aging treatments (T6, RRA, and FSA) are presented and characterized in this research. SiO₂ combined with stearic acid (STA) modified by KH550 was utilized to achieve multifunctional superhydrophobic coatings. Adhesive tape adhesion, blade scratch, and mechanical wear tests were utilized to assess the durability of the superhydrophobic coatings. The results showed that the prepared coatings exhibited excellent superhydrophobicity, self-cleaning ability, and mechanical properties, especially the T6 temper alloy. This alloy had the largest CA value (156.5°) and the lowest SA value (4.3°). The composite coatings still exhibited excellent superhydrophobicity under mechanical damage. Furthermore, the alloys with STA/SiO₂ displayed marvelous corrosion resistance efficiency. The T6 temper alloy with a protection rate of 73.8% had an approximately one-order-of-magnitude decrement in carrion current density. The composite coating can be effectively utilized in various industrial fields, thus extending its potential impact. Full article

The microstructure and mechanical properties of semi-continuous casting Mg-Gd-Y-Zr magnesium alloys with different Zn contents were studied in this paper. The results showed that an increase in Zn content resulted in gradual refinement of the grains and a gradual increase in the volume fraction of the second phase. At a Zn content of 0.7 wt%, the microstructure was mainly composed of the α-Mg matrix and the Mg5(GdY) and long-period stacking order (LPSO) phases. An increase in the Zn content lowered the volume fraction of the Mg5(GdY) phase and increased the volume fraction of the LPSO phase. At a Zn content of 3.3 wt%, the microstructure was mainly composed of the α-Mg matrix and the LPSO phase. Among these alloys, the alloy without Zn addition showed an optimal ultimate tensile strength and yield strength of 229 MPa and 185 MPa, respectively, while the alloy with 3.3 wt% Zn showed an excellent elongation after fracture of 4.5%. The tensile fracture analysis indicated that the cracks of the alloy without Zn mainly originated at the trigeminal junction of the grain boundary, the cracks of the 0.7 wt% Zn and 1.5 wt% Zn alloy mainly originated at the interface of the Mg/lamellar LPSO phase, and the cracks of the 3.3 wt% Zn alloy mainly originated at the bulk LPSO phase of the grain boundary and then propagated along the bulk LPSO phase. Full article

This article deals with the simple preparation of environmentally friendly acrylic latex binders, which are functionalized with nanoparticles of metal oxides, namely MgO, ZnO, La₂O₃ and combinations of MgO and ZnO, serving as functional components to achieve antimicrobial properties, but also to improve physical–mechanical properties and chemical resilience. The incorporation of uncoated powder nanoparticles was performed during the synthesis, using the two-stage semi-continuous emulsion radical polymerization technique, to obtain latexes containing 0.5%–1.3% nanoparticles relative to the polymer content. Changes in latex performance due to nanoparticles were compared from the point of view of the type and concentration of metal oxide nanoparticles in latex. The results of the tests showed that all types of nanoparticles showed very promising properties, while with increasing concentration of nanoparticles there was an improvement in properties. The nanoparticles in latex provided interfacially crosslinked transparent smooth coating films with high gloss and good physical–mechanical properties. Latexes containing the highest concentration of nanoparticles provided coatings with significant antimicrobial activity against all tested bacterial and fungal strains, but also in-can preservative stability of liquid latex. Furthermore, the coatings were resistant to solvents, and in addition, latexes with MgO nanoparticles showed a significant decrease in the minimum film-forming temperature, and latex with a concentration of about 1.3% MgO did not show any flash corrosion under the coating film cast on a steel substrate. The latexes containing MgO and La₂O₃ nanoparticles provided coatings that were very resistant to water bleaching. Full article

Antifriction alloys such as AlSn20Cu are key material options for sliding bearings used in machinery. Uniform distribution and a near-equiaxed granularity tin phase are generally considered to be ideal characteristics of an AlSn20Cu antifriction alloy, although these properties vary by fabrication method. In this study, to analyze the variation of the microstructure with the fabrication method, AlSn20Cu alloys are prepared by three methods: semi-continuous casting, semi-solid die casting, and spray forming. Bearing blanks are subsequently prepared from the fabricated alloys using different processes. Morphological information, such as the total area ratio and average particle diameter of the tin phase, are quantitatively characterized. For the tin phase of the AlSn20Cu alloy, the deformation and annealing involved in semi-continuous casting leads to a prolate particle shape. The average particle diameter of the tin phase is 12.6 µm, and the overall distribution state is related to the deformation direction. The tin phase of AlSn20Cu alloys prepared by semi-solid die casting presents both nearly spherical and strip shapes, with an average particle diameter of 9.6 µm. The tin phase of AlSn20Cu alloys prepared by spray forming and blocking hot extrusion presents a nearly equilateral shape, with an average particle diameter of 6.2 µm. These results indicate that, of the three preparation methods analyzed in this study, semi-solid die casting provides the shortest process flow time, whereas a finer and more uniform tin-phase structure may be obtained using the spray-forming process. The semi-solid die casting method presents the greatest potential for industrial application, and this method therefore presents a promising possibility for further optimization. Full article

Aiming at the problem that melt inclusions in the casting process of 7085 aluminum alloy seriously affect the ingot quality, this study introduces ultrasonic bending vibration into the melt of the launder in the semi-continuous casting process of 7085 aluminum alloy and investigates the online purification effect of ultrasonic bending vibration on the melt of 7085 aluminum alloy through a metallographic analysis, SEM analysis, and EDS energy spectrum analysis. The results show that, under the action of the ultrasonic, the inclusions in the aluminum melt are transformed from a large number of elongated large inclusions with a size of more than 50 μm, and granular inclusions with a size of about 5–15 μm, into a small amount of smaller than 30 μm point-like small inclusions. In addition, the average area ratio of inclusions in the melted sample was reduced from 3.835 (±0.05)% to 0.458 (±0.05)%, and the residual refining agent in the aluminum melt was effectively removed. It was also found that under the action of ultrasonic bending vibration, the tiny inclusions in the melt aggregate with each other, and interact with the residual refining agent in the melt to further grow, and are attached to the inner surface of the ceramic cavity channel to be removed. Full article

Dissoluble magnesium alloys for fabrication of fracturing tools have received increasing attention in recent years. However, most of the existing research is focused on the small-sized samples prepared in the laboratory, and there is almost no report on the industrial dissoluble magnesium alloys. In this study, large-scale Mg-Al-Zn-Mn-Ca-Ni alloys with a diameter of 110 mm were prepared by a semi-continuous casting and two-step extrusion method, and the corresponding microstructure and mechanical and corrosion properties were also investigated. It was found that after two-step extrusion, the mainly precipitate phases in the Mg-Al-Zn-Mn-Ca-Ni alloy are bulk-like AlMnNi, strip-like Al₃Ni, and granular-like and lamellar-like Mg₁₇Al₁₂ phases. Due to the combined effects of grain refinement and precipitation strengthening, the Mg-Al-Zn-Mn-Ca-Ni alloy obtained excellent mechanical properties after two-step extrusion, and its ultimate tensile strength, yield strength, and elongation were 314.6 MPa, 191.2 MPa, and 13.1%, respectively. Moreover, the corrosion rate of the alloy in 3 wt.% KCl at 93 °C was as high as 97.61 mg·cm⁻²·h⁻¹. This work provides a high-performance, low-cost, and large-scale alloy product for the fabrication of dissoluble fracturing tools. Full article

Mg-Al-Ca-Mn alloys with Ca/Al ≥ 1 of AX33, AX44, and AX55 were prepared by combining three processes of water-cooling semi-continuous cast, homogenization heat treatment, and hot extrusion. The as-fabricated alloys translated into composites consisting of α-Mg solid solution + granular Al₂Ca. These alloys exhibited some favourable properties such as a tensile strength of 324~350 MPa at room temperature and 187~210 MPa at elevated temperature of 423 K, an ignition temperature of 1292~1344 K, and so on. Variation trend between performance and content of Al and Ca is given in this paper. The result indicated that the emerged second-phase Al₂Ca in the alloys was beneficial to the improvement in mechanical properties, heat resistance, flame retardation, and corrosion resistance. Full article

The rise of metal additive manufacturing technology has increased the demand for high-performance alloys such as metal matrix composites (MMCs). The metallurgical production of MMCs remains a challenge. The nano-powder of dielectric particles does not mix well into the liquid metal because of several reasons. On a macroscopic level, the powder is rejected by the molten metal through buoyancy and surface tension forces. On a microscopic level, the particles are held together by Van der Waals forces forming particle agglomerates. Our research strategy is to address these issues separately in two steps. We are investigating an electromagnetically assisted MMC casting method for the production of particle-strengthened, directionally solidified aluminum alloys. In the first step, nanoparticles are mixed into melt while it is in a semi-solid state by efficient permanent magnet stirrers. Then, the alloy is subjected to ultrasound treatment for fine particle dispersion. Semi-continuous casting of MMC is used to obtain material for additive manufacturing process. Material is cast in 6–20 mm rods by a direct chill casting method and can be made into wire with the application of wire-feed additive manufacturing. We investigate the possibility of improving Al alloy SiC composite material properties by applying electromagnetic interactions during solidification. Electric current and a moderate static magnetic field (0.1–0.5 T) creates melt convection in mushy zone. Such interaction enhances heat and mass transfer near the solidification interface and hinders the re-agglomeration of the added particles. Full article

The deformation behaviour of as-cast ZK40 alloys modified with individual additions of Ca and Gd is investigated at 250 °C and 300 °C. Compression tests were carried out at 0.0001 s⁻¹ and 0.001 s⁻¹ using a modified Gleeble system during in-situ synchrotron radiation diffraction experiments. The deformation mechanisms are corroborated by post-mortem investigations using scanning electron microscopy combined with electron backscattered diffraction measurements. The restoration mechanisms in α-Mg are listed as follows: the formation of misorientation spread within α-Mg, the formation of low angle grain boundaries via dynamic recovery, twinning, as well as dynamic recrystallisation. The Gd and Ca additions increase the flow stress of the ZK40, which is more evident at 0.001 s⁻¹ and 300 °C. Dynamic recovery is the predominant restoration mechanism in all alloys. Continuous dynamic recrystallisation only occurs in the ZK40 at 250 °C, competing with discontinuous dynamic recrystallisation. Discontinuous dynamic recrystallisation occurs for the ZK40 and ZK40-Gd. The Ca addition hinders discontinuous dynamic recrystallisation for the investigated temperatures and up to the local achieved strain. Gd addition forms a semi-continuous network of intermetallic compounds along the grain boundaries that withstand the load until their fragmentation, retarding discontinuous dynamic recrystallisation. Full article

New and more complex casting technologies are growing, and foundries are using innovative methods to reduce cost and energy consumption and improve their product qualities. Numerical techniques, as tools to design and examine the process improvements, are also evolving continuously to embrace modelling of more dynamic systems for industrial applications. This paper will present a fresh approach towards the numerical simulation of dynamic processes using an evolving and dynamic mesh technique. While the conventional numerical techniques have been employed for these dynamic processes using a fixed domain approach, the more realistic evolving approach is used herein to match the complex material processes in new foundries. The underpinning of this new dynamic approach is highlighted by an evolving simulation environment where multiple mesh entities are appended to the existing numerical domain at timesteps. Furthermore, the change of the boundary and energy sources within casting process simulations have rationally been presented and its profound effects on the computational time and resources have been examined. The discretization and solver computational features of the technique are presented and the evolution of the casting domain (including its material and energy contents) during the process is described for semi-continuous casting process applications. Full article

The effect of low-frequency electromagnetic fields on the micro-structure and macro-segregation of 5A90 alloy ingots during the semi-continuous casting process were quantitatively investigated. The ingots of a 5A90 alloy with a diameter 170 mm were produced by the conventional direct chill casting (DCC) process and low-frequency electromagnetic casting (LFEC) with 10 Hz/100 A. The results showed that LFEC can substantially refine the micro-structure and shorten the width of the columnar grain area of an ingot. The refinement effect came with the relieving of grain boundary segregation and an improvement in the macro-segregation of the ingot. Compared with the traditional DCC process, the tensile properties of the aged alloy prepared by the LFEC process were improved due to the effects of the increase in solid solubility and the strengthening of the grain refinement, so that the stability of the tensile properties was also improved. Meanwhile, the rate of yield increased by 2.3% with a decrease in the peeling thickness of the ingot. Full article

In order to achieve long-term and stable ultrasonic treatment in the direct chill semi-continuous casting process, a new L-shaped ceramic ultrasonic wave guide rod is designed to introduce ultrasonic bending vibration into 2A14 aluminum alloy melt. The effect of ultrasonic bending vibration on the solidification structure and composition segregation of large 2A14 aluminum alloy ingots (φ 830 mm × 6000 mm) in the process of semi-continuous casting were studied by means of a direct reading spectrometer, scanning electron microscope, metallographic microscope, and hardness test. The ultrasonic ingot treated by bending vibration was compared with the ingot without ultrasonic treatment and the ingot treated by the traditional straight-rod titanium alloy wave guide rod. The results show that, during the solidification of 2A14 aluminum alloy, ultrasonic treatment can significantly refine the grain, break up the agglomerated secondary phase, and make its distribution uniform. The macro-segregation degree of solute including the negative segregation at the edge of the ingots and the positive segregation in the center can be reduced. Through comparative analysis, the macrostructure of the ingot, treated by the L-shaped ceramic ultrasonic wave guide rod, was found to be better than that of the ingot treated by the traditional straight-rod titanium alloy wave guide rod. In particular, the grain refinement effect at the edge of the ingot was the best, the secondary phase was smaller, more solute elements can be dissolved into the α-Al matrix, and the ability of the L-shaped ultrasonic wave guide rod to restrain segregation was stronger at the edge of the ingot. Full article

A new elevated-temperature high-strength Mg–4Er–2Y–3Zn–0.4Mn (wt %) alloy was developed by semi-continuous casting, solid solution treatment, and hot extrusion. W phase (Mg₃(Er,Y)₂Zn₃) with fcc structure, long period stacking ordered phases with 18R (Mg₁₀(Er,Y)₁Zn₁) and 14H (Mg₁₂(Er,Y)₁Zn₁) structures, and basal plane stacking faults (SFs) was formed in the as-cast alloy, mainly due to the alloy component of (Er + Y)/Zn = 1:1 and Er/Y = 1:1 (at %). After solid solution treatment and hot extrusion, the novel microstructure feature formed in as-extruded alloy is the high number-density nanospaced basal plane SFs throughout all the dynamically recrystallized (DRXed) and un-DRXed grains, which has not been previously reported. The as-extruded alloy exhibits superior tensile properties from room temperature to 300 °C. The tensile yield strength can be maintained above 250 MPa at 300 °C. The excellent elevated-temperature strength is mainly ascribed to the formation of nanospaced basal plane SFs throughout the whole Mg matrix, fine DRXed grains ~2 μm in size, and strongly basal-textured un-DRXed grains with profuse substructures. The results provide new opportunities for the development of deformed Mg alloys with satisfactory mechanical properties for high-temperature services. Full article

Oxide films or inclusions can reduce the continuity and integrity of materials and they always lead to a significant reduction in the mechanical properties of an aluminum alloy. They can greatly reduce the plastic flow behavior of materials, thus affecting the subsequent processing performance. Therefore, an effective ultrasonic assisted preparation technology has been applied to industrial manufacturing of large-scale aluminum alloy ingots (with diameter: Φ = 1250 mm and height: h = 3750 mm). However, the mechanisms of ultrasonic purification on the large-scale ingots are not clear. Therefore, a number of aluminum alloy casting experiments were carried out to produce a conventional hot top semi-continuous ingot (CHTI) and an ultrasonic hot top semi-continuous ingot (UHTI) in this work. The microstructures of CHTI and UHTI were analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). The results indicated that there were some oxide film defects in the CHTI but some finely dispersed inclusion particles were discovered in the UHTI. The X-ray diffraction (XRD) data showed that the component of inclusion was Al₂O₃. According to the different cavitation effects of the different areas of the molten aluminum, the process of ultrasonic purification was divided into three periods and the mechanisms in each period were separately studied. Full article