Search Results (12)

In this work, the Al/Mg bimetals were prepared by traveling magnetic field (TMF)-assisted compound casting, and the effects of current intensity on the interfacial microstructure and mechanical properties of the Al/Mg bimetals were investigated. The results revealed that the Al/Mg bimetallic interface without the TMF consisted of an Al-Mg intermetallic compounds (IMCs) area (Al₃Mg₂ + Al₁₂Mg₁₇ + Mg₂Si particles) and Al-Mg eutectic area (Al₁₂Mg₁₇ + δ-Mg). There was no change in the interfacial phase compositions with the TMF, but the interface thickness initially decreased and then increased with the increase in the TMF current, and the distribution of Mg₂Si became more uniform, dendrites become smaller, and dendritic arms fragment. The shear strength improves from 17 MPa without the TMF to 27 MPa with the TMFed-60 A, which was increased by 58.8%. This enhancement occurs because cracks are deflected by uniformly distributed Mg₂Si particles and do not coalesce into main cracks, ultimately fracturing in the eutectic region, which increases the length of the crack propagation path and thereby improves the shear strength of the Al/Mg bimetals. Full article

To enhance the interfacial performance of Al/Mg bimetal, this study introduced a novel Mo coating and employed an ultrasonic field (UF) to regulate the interfacial microstructure. In the absence of both a Mo coating and ultrasonic treatment (referred to as the untreated specimen), the interfacial region was primarily composed of Al-Mg intermetallic compounds (Al-Mg IMCs), Al-Mg eutectic structures (ES), and Mg₂Si phases, with an average interfacial layer thickness of approximately 1623 μm. Upon application of the Mo coating, the formation of both Al-Mg phases and Mg₂Si phases was completely inhibited. The interfacial zone was predominantly characterized by the Mo solid solution (Mo SS) and oxide, with the average thickness significantly reduced to about 28 μm. Upon applying the UF to the Mo-coated specimen, the interfacial composition remained similar to that of the untreated specimen, except for Mo SS, with the interfacial thickness increasing to 561 μm. Shear strength tests indicated that the application of the Mo coating alone resulted in a decrease in bonding strength compared to the untreated specimen. However, subsequent ultrasonic treatment significantly improved the interfacial shear strength to 54.7 MPa, representing a 60.9% increase relative to the untreated specimen. This improvement is primarily attributed to the Mo coating and UF synergistically suppressing the formation of brittle Al-Mg IMCs and reducing oxide inclusions at the interface. Thus, the simultaneous application of Mo coatings and ultrasonic fields is required to enhance the properties of Al/Mg bimetals. Full article

Bimetals have broad application prospects in many fields due to the combination of the performance characteristics of the two materials, but weak interface bonding limits their promotion and application. Therefore, studying the interfacial behavior to achieve bimetallic strengthening is the focus of this field. However, it is often difficult or costly to visually observe the interfacial behavior using traditional experimental methods. Molecular dynamics (MD) is an advanced microscopic simulation method that can conveniently, rapidly, accurately and intuitively study the diffusion and mechanical behavior at the bimetallic interfaces, providing a powerful tool and theoretical guidance to reveal the nature of interfacial bonding and the strengthening mechanism. This paper summarizes the research progress on molecular dynamics in the bimetallic formation process and mechanical behavior, including Al/Cu, Al/Mg, Al/Ni, Al/Ti, Al/Fe, Cu/Ni, and Fe/Cu. In addition, the future development direction is outlined to provide theoretical basis and experimental guidance for further exploring the formation process and performance enhancement of the bimetallic interfaces. Full article

Understanding trends in the formation of the intermetallic compound (IMC) layer in Al/Fe bimetallic composites can aid in significantly improving their mechanical properties. However, it is currently challenging to predict IMC layer formation during hot-dip aluminizing. Furthermore, the results from previous studies are difficult to compare owing to the variation in the process parameters used. Therefore, to understand how temperatures and holding times affect the thickness and hardness properties of IMC layers, we investigated the interfacial properties of aluminized stainless steel in molten Al-Si-Mg. AISI 420 stainless steel was hot-dip aluminized in an Al–Si–Mg alloy melt for 10–120 min at four different temperatures: 700, 750, 800, and 850 °C. Morphology, type, and element distribution of the phases formed in the reaction layer and the reduction rate of the aluminizing process were studied. Notably, while the reaction layer thickness increased with increasing aluminizing temperature when the holding time was low, long-term reaction caused the reaction layer to become thicker at lower temperatures. The mechanism of this morphological transformation is discussed. The results demonstrated effective trends in controlling the morphology of the intermetallic compound layer with respect to various hot-dip Al plating process parameters. Full article

In this work, ultrasonic vibration treatment (UVT) was introduced to improve the interfacial microstructure and bonding strength of A356/AZ91D bimetal processed via lost foam compound casting (LFCC). The interfacial microstructure and mechanical properties of the Al/Mg bimetal processed via LFCC with different UVT durations were investigated. Results revealed the UVT did not change the composition of phases at the interface. The Al/Mg bimetallic interface consisted of an intermetallic compound area (β-Al₃Mg₂ + γ-Al₁₂Mg₁₇ + Mg₂Si) and eutectic area (δ-Mg + γ-Al₁₂Mg₁₇ + Mg₂Si). When the duration of the UVT was increased, the gathered Mg₂Si particles at the intermetallic compound area were refined to sizes of no more than 5 μm and became more homogeneously dispersed in the intermetallic compound area and diffused in the eutectic area, which could be attributed to the removal of oxide film and the acoustic cavitation and streaming flow effects induced by the UVT. The microhardness of the Al/Mg bimetallic interface was not obviously changed by the increase in UVT duration. The shear strength of the Al/Mg bimetal was increased with UVT and reached maximum with a UVT duration of 5 s, with a value of 56.7 MPa, which was increased by 70.3%, compared with Al/Mg bimetal without UVT. This could be attributed to the removal of the oxide film at the Al/Mg bimetallic interface, which improved the metallurgical bonding of the Al/Mg interface. Additionally, the refined and homogeneously dispersed Mg₂Si particles played an important role in suppressing the propagation of cracks and enhancing the shear strength of the Al/Mg bimetal. Full article

Vibration was adopted to enhance the interface bonding of Mg–Al bimetal prepared by the lost foam compound casting (LFCC) technique. The Mg–Al bimetallic interface was composed of three layers: layer I (Al₃Mg₂ and Mg₂Si phases), layer II (Al₁₂Mg₁₇ and Mg₂Si phases), and layer III (Al₁₂Mg₁₇ + δ-Mg eutectic structure). With the increase in vibration acceleration, the cooling rate of the Mg–Al bimetal increased, resulting in the decrease in the reaction duration that generates the intermetallic compounds (IMCs) layer (including layers I and II) and its thickness. On the other hand, the Mg₂Si phase in the IMCs layer was refined, and its distribution became more uniform with the increase in the vibration acceleration. Finally, the shear strength of the Mg–Al bimetal continued to increase to 45.1 MPa when the vibration acceleration increased to 0.9, which was 40% higher than that of the Mg–Al bimetal without vibration. Full article

Phosphorus (P) pollution and phosphorus recovery are important issues in the field of environmental science. In this work, a novel Al-Ti bimetal composite sorbent was developed via a cost-effective co-precipitation approach for P removal from water. The adsorptive performance and characteristics of P onto Al-Ti sorbent were evaluated by batch adsorption experiments. The effects of Al:Ti molar ratio, initial P concentration and reaction temperature were investigated. The microstructural characteristics of the Al-Ti sorbent were confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and nitrogen adsorption-desorption measurements. Kinetic studies showed that the adsorption of P on Al-Ti oxide proceeds according to pseudo-second-order kinetics. The maximum adsorption capacity of phosphate on the Al-Ti oxide calculated from linear Langmuir models was 68.2 mg-P/g at pH 6.8. The Al-Ti oxide composite sorbent showed good potential for P recovery, owing to its large adsorption capacity and ease of regeneration. Full article

The current study introduces a method for manufacturing steel–aluminum bearing bushings by compound forging. To study the process, cylindrical bimetal workpieces consisting of steel AISI 4820 (1.7147, 20MnCr5) in the internal diameter and aluminum 6082 (3.2315, AlSi1MgMn) in the external diameter were used. The forming of compounds consisting of dissimilar materials is challenging due to their different thermophysical and mechanical properties. The specific heating concept discussed in this article was developed in order to achieve sufficient formability for both materials simultaneously. By means of tailored heating, the bimetal workpieces were successfully formed to a bearing bushing geometry using two different strategies with different heating durations. A metallurgical bond without any forging defects, e.g., gaps and cracks, was observed in areas of high deformation. The steel–aluminum interface was subsequently examined by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was found that the examined forming process, which utilized steel–aluminum workpieces having no metallurgical bond prior to forming, led to the formation of insular intermetallic phases along the joining zone with a maximum thickness of approximately 5–7 µm. The results of the EDS analysis indicated a prevailing Fe_xAl_y phase in the resulting intermetallic layer. Full article

Bimetallic materials are important in many industries (aerospace, medicine, etc.) since they allow the creation of constructions that combine specific functional properties, for example, low density (aluminum alloy) and high corrosion resistance (stainless steel), due to layering fabrication of the bimetallic joint. On the other hand, the difference in thermophysical properties of the dissimilar material layers leads to residual stresses, which cause deformation and destruction of such a bimetallic joint produced via the methods of surfacing or additive technologies. This article discusses the methods based on the gray relational analysis and generalized desirability function for the quality assessment of Al–10Si–Mg aluminum alloy and Cr18–Ni10–Ti stainless-steel bimetal fabricated via selective laser melting (SLM). There are four main parameters (quality indices) of the quality generalized assessment, which determine the degree of Al penetration into the steel substrate and Fe into the deposited layer, the difference in microhardness values on both sides of the interface boundary, and the resistance to mechanical destruction of the bimetallic joint. According to the results obtained, the best set of quality indices corresponds to the SLM technological modes with an energy density of 105 and 147 J/mm³. The greatest functionality of the bimetals is determined by the quality index associated with its strength. Therefore, methods of gray relational analysis and desirability function make it possible to form a generalized assessment for the bimetallic joint quality and, consequently, to select the best technological mode. Full article

This paper studies the weld interface microstructure and mechanical properties of AlMg6-stainless steel and AlMg6-titanium bimetals produced using explosive welding. The microhardness (HV), tear strength, and microstructure of the weld seams were evaluated. The interface of the weld zones had a flat profile. No structural disturbances or heterogeneity in the AlMg6-titanium weld interface were observed. On the other hand, the bimetal AlMg6-stainless steel had extensive zones of cast inclusions in the 10–30 µm range. SEM/energy-dispersive X-ray spectroscopy (EDS) analysis showed the presence of a hard and brittle intermetallic compound of Al and FeAl₃ (with 770–800 HV). The microhardness of the AlMg6-titanium bimetal grew higher closer to the weld interface and reached 207 HV (for AlMg6) and 340 HV (for titanium). Both bimetals had average tear strength below 100 MPa. However, the tear strength of some specimens reached 186 and 154 MPa for AlMg6-titanium and AlMg6-stainless steel, respectively. It is also worth mentioning that heat treatment at 200 °C for one hour led to a uniform distribution of tear strength along the entire length of the bimetals. The study shows that one of the possible solutions to the problem of the formation of the brittle intermetallic compounds would be the use of intermediate layers of refractory metals. Full article

A novel technique combining solid–liquid compound casting (SLCC) with arc spraying was designed to manufacture the arc-sprayed Al/AZ91D bimetals with a Zn interlayer. The Al/Mg bimetal was produced by pouring the AZ91D melt into the molds sprayed with Al/Zn double-deck coating, during which the arc-sprayed Zn coating acted as the interlayer. The effect of the Zn interlayer on microstructures, properties, and fracture behaviors of arc-sprayed Al/AZ91D bimetals by SLCC was investigated and discussed in this study. The optimal process parameter was acquired by analyzing the results from different combinations between the arc-spraying time of the Zn coating (10, 18, and 30 s) and the preheat time of the Al/Zn double-deck coating (6 and 12 h). The interfacial microstructures of the arc-sprayed Al/AZ91D bimetals with a Zn interlayer could be approximately divided into two categories: One was mainly composed of (α-Mg + Al₅Mg₁₁Zn₄) and (α-Al + Mg₃₂(Al, Zn)₄₉) structures, and the other primarily consisted of (α-Mg + Al₅Mg₁₁Zn₄), (MgZn₂ (main) + β-Zn), and (β-Zn (main) + MgZn₂) structures. In the interface zone, the (α-Mg + Al₅Mg₁₁Zn₄) structure was the most abundant structure, and the MgZn₂ intermetallic compound had the highest microhardness of 327 HV. When the arc-spraying time of the Zn coating was 30 s and the preheat time of the Al/Zn double-deck coating was 6 h, the shear strength of the arc-sprayed Al/AZ91D bimetal reached 31.73 MPa. Most rupture of the arc-sprayed Al/AZ91D bimetals with a Zn interlayer occurred at the (α-Mg + Al₅Mg₁₁Zn₄) structure and presented some typical features of brittle fracture. Full article

With respect to its density, magnesium (Mg) has a high potential for lightweight components. Nevertheless, the industrial application of Mg is limited due to, for example, its sensitivity to corrosion. To increase the applicability of Mg, a process chain for the production of a Mg component with a complete aluminum (Al) cladding is presented. Hydrostatic co-extrusion was used to produce bar-shaped rods with a diameter of 20 mm. The bonding between the materials was verified by ultrasonic testing. Specimens with a length of 79 mm were cut off from the rods and forged by using a two-staged process. After the first step (Heading), the Mg core was removed partially by drilling to ensure a complete enclosing of the remaining Mg during the second forging step (Net shape forging). The geometry of the drilling hole and the heading die design were dimensioned with the Finite Element-simulation software FORGE. Hence, a complete Al-enclosed Mg component was achieved by using the described process chain and forming processes. Microstructural investigations confirm the formation of an intermetallic interface as expected. Full article