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Copyright of Journal of Chongqing University of Technology (Natural Science) is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compound casting is a process in which a single component is made from two metallic materials, such as aluminum and steel. Solid-liquid bimetallic compounds can be produced by suitable process control. This technology can reduce the number of joining processes, and the specific properties of the respective metal component can be used for specifically designed product properties, for example, where lightweight and high strength are needed. This paper presents an experimental methodology for producing a purely material-bonded bimetallic joint from cast aluminum and zinc-coated sheet steel in 3D sand casting using an inductive heating system. The process-related temperature characterisation in the compound zone is described using a heating test rig and temperature measurements. It shows that inductive preheating can only produce a material bond between the aluminum casting and the coated steel sheet. Shear tensile tests showed strengths between 15 MPa and 22 MPa. Laser surface pre-treatment using laser ablation cutting on the coated steel sheet was carried out to investigate the benefit of possible microform-locking. The results show a strength-reducing influence on the tensile shear tests. Micrographs showed the formation of Al4.5FeSi and Al7Fe2Si, as well as the formation of other undefined intermetallic phases. The thickness of the compound zone is 10 µm. [ABSTRACT FROM AUTHOR]

In this paper, 6061-T6 aluminum alloy and 30CrMnSiA steel are bonded by inertia radial friction welding (IRFW). The formation mechanism of the aluminum/steel friction welded joints and the effect of the welding parameters on the mechanical properties are investigated through the microstructure, microzone composition, and mechanical property analysis. The results show that no visible intermetallic compound layers (IMCs) are detected on the aluminum/steel welding interface, which may be due to Si element aggregating in the welding interface and then forming a Al−Fe−Si phase, preventing the formation and growth of an Al−Fe IMCs. Eventually, a micron ultrathin interface reaction layer composed of Al0.7Fe3Si0.3, FeAl, and Fe3Al phases is formed at the aluminum/steel welding interface. The maximum average shear strength of the joint is 176 MPa. The shear fracture is a typical ductile fracture. Properly reducing the friction speed and increasing the upsetting pressure can improve the bonding strength of aluminum/steel joints. [ABSTRACT FROM AUTHOR]

A novel ultrasonic vibration enhanced friction stir welding (UVeFSW) process was employed to join the 6061-T6 aluminum alloy and QP980 high-strength steel. The macro morphology, microstructure and tensile shear properties of the joint with or without ultrasonic energy were compared and analyzed. Meanwhile, the effects of ultrasonic energy on the welding load were studied. The results show that the ultrasonic vibration applied to the base metal before welding can soften the base metal, promote the plastic flow of the material, expand interface zone and nugget zone of the aluminum/steel, make more steel particles rotate into the aluminum alloy side with the stirring needle, forming a hook structure at the edge of the interface zone which can improve the failure load of the joint. The fracture position and fracture morphology of FSW joint are changed by ultrasonic, and the mechanical properties of FSW joint are improved. Under the welding parameters conducted in the experiment, the maximum average failure load of the joint is 4.99 kN. Under the conditions of a welding rate of 90 mm/min and a depth of 0.1 mm, the application of ultrasonic vibration makes the average failure load of the joint increase by 0.98 kN and the tensile shear performance increase by 28.24%. After applying ultrasonic vibration, the axial force Fz, the tool torque Mt and the spindle power decrease by 2.46%, 6.44% and 4.59% respectively.

Wire and arc additive manufacturing (WAAM) provides a convenient solution for the integrated design and manufacturing of Al/steel structures. The multiple thermal cycles inherent in WAAM can affect the Al/steel interface and ultimately the overall performance of the Al/steel structure. Herein, the evolution behavior of the Al/steel interface microstructure under different WAAM modes, number of thermal cycles, and interpass temperature is investigated. The results show that the process of heat accumulation plays an important role in the evolution of Al/steel interface. As the number of thermal cycles increases, the intermetallic compounds layer gradually transforms from the mainly τ5‐Al8Fe2Si phase to (Al, Si)13(Fe, Cr)4 phase. The rise of interpass temperature significantly aggravates the microstructural evolution process, but the final interface structure can be manipulated employing temperature control. When the interpass temperature is lower than 250 °C, the formation of the brittle Fe2Al5 phase is avoided. With the increase of thermal cycles, the shear strength of Al/steel additive specimens increases first, then decreases, and finally tends to be stable. The changes in shear strength are closely related to the interface microstructures. [ABSTRACT FROM AUTHOR]

An ultrasonic-assisted resistance spot welding process, which can improve the quality of aluminum/steel spot-welded joints, has been developed. However, the mechanism of the thermal-electrical-mechanical behavior caused by the ultrasonic longitudinal vibration to welding process has not been clarified. In this study, the role and impact mechanisms of ultrasonic longitudinal vibration during the welding process to form joints were confirmed by combining the microstructural characterization of the formed joints with the signal analysis of the process, as well as the analysis of the independent finite element numerical calculation results. Additionally, the interface metallurgical reaction behavior, welding defects, fracture behavior, and joint strength characteristics of ultrasonic-assisted aluminum/steel resistance spot welding joints were comprehensively analyzed, and the results indicated that the sizes of the aluminum/steel nuggets decreased. It could be attributed to the competition among multiple ultrasonic effects. Specifically, ultrasonic vibration decreased the contact resistance between the aluminum/steel sheets, whereas the acoustic cavitation and acoustic streaming effects increased the electrical conductivity of molten steel and thermal conductivity of molten aluminum, respectively. Moreover, ultrasonic vibration promoted the radial creep of molten and near-molten aluminum, which expanded in the effective bonding area between the two workpieces. Furthermore, ultrasonic vibration effectively reduced the thickness of the intermetallic compound layer (<3.0 µm), concurrently inhibited the formation of interfacial welding defects. Finally, the peak tensile-shear load of aluminum/steel joints is significantly increased under multiple ultrasonic optimization mechanisms. [Display omitted] • The ultrasonic effects are introduced into the computational model for aluminum/steel resistance spot welding process. • The effect mechanisms of ultrasonic vibration on the aluminum/steel resistance spot welding process were explored. • Ultrasonic vibration facilitates the radial creep of molten and near-molten aluminum, which can expand the bonding area. • Ultrasonic vibration decreases nugget sizes by reducing contact resistance, increasing thermal and electrical conductivity. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Materials Engineering / Cailiao Gongcheng is the property of Journal of Materials Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Compound casting is a process in which a single component is made from two metallic materials, such as aluminum and steel. Solid-liquid bimetallic compounds can be produced by suitable process control. This technology can reduce the number of joining processes, and the specific properties of the respective metal component can be used for specifically designed product properties, for example, where lightweight and high strength are needed. This paper presents an experimental methodology for producing a purely material-bonded bimetallic joint from cast aluminum and zinc-coated sheet steel in 3D sand casting using an inductive heating system. The process-related temperature characterisation in the compound zone is described using a heating test rig and temperature measurements. It shows that inductive preheating can only produce a material bond between the aluminum casting and the coated steel sheet. Shear tensile tests showed strengths between 15 MPa and 22 MPa. Laser surface pre-treatment using laser ablation cutting on the coated steel sheet was carried out to investigate the benefit of possible microform-locking. The results show a strength-reducing influence on the tensile shear tests. Micrographs showed the formation of Al4.5FeSi and Al7Fe2Si, as well as the formation of other undefined intermetallic phases. The thickness of the compound zone is 10 µm.

In this paper, 6061-T6 aluminum alloy and 30CrMnSiA steel are bonded by inertia radial friction welding (IRFW). The formation mechanism of the aluminum/steel friction welded joints and the effect of the welding parameters on the mechanical properties are investigated through the microstructure, microzone composition, and mechanical property analysis. The results show that no visible intermetallic compound layers (IMCs) are detected on the aluminum/steel welding interface, which may be due to Si element aggregating in the welding interface and then forming a Al−Fe−Si phase, preventing the formation and growth of an Al−Fe IMCs. Eventually, a micron ultrathin interface reaction layer composed of Al0.7Fe3Si0.3, FeAl, and Fe3Al phases is formed at the aluminum/steel welding interface. The maximum average shear strength of the joint is 176 MPa. The shear fracture is a typical ductile fracture. Properly reducing the friction speed and increasing the upsetting pressure can improve the bonding strength of aluminum/steel joints.

• The high quality welding of aluminum alloy and steel was realized. • The effect of ultrasonic vibration on the quality of aluminum/steel FSW joints was expounded. • The optimal ultrasonic power of aluminum/steel UVeFSW was explored. • The relationship between microstructure and properties of aluminum/steel UVeFSW joints was revealed. The optimization mechanism of ultrasonic power on the performance of aluminum/steel dissimilar metal ultrasonic vibration enhanced friction stir welding (UVeFSW) joints was studied. The results indicated that ultrasonic vibration can significantly improve the surface forming quality of the weld seam, increase the width of the joint interface zone, adjust the height of the hook structure, suppress the generation of intermetallic compounds, and enhance the failure load of the joints. When the ultrasonic power was 500 W, the lap joints with the best mechanical properties were obtained, and its failure load was 5.14 kN, which was 51.2% higher than that of conventional FSW (0 W). [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) and ultrasonic vibration enhanced friction stir welding (UVeFSW) were used to connect 3 mm thick 2024-T3 Al alloy and Q235 carbon structural steel. The weld forming quality, mechanical properties, fracture location and interface behavior of the whole and layered joints were compared and analyzed, and the different mechanisms of the ultrasonic vibration to improve the tensile strength of the joint were summarized. As the results show, the ultrasonic vibration promoted the plastic flow ability of materials and improved the welding seam forming quality. Moreover, the ultrasonic vibration made the plastic deformation of the material in the nugget zone more uniform, which improved the strength of the nugget zone. In the middle layer of the joint, the ultrasonic vibration reduced the thickness of intermetallic compound layers (IMCLs), eliminated the laminated structure that harmed the connection quality of the joint, and formed a micromechanical interlocking structure in which IMCLs was inserted into the steel, which improved the interfacial bonding strength and improved the tensile strength by 11.1%. The ultrasonic vibration optimized the macro-mechanical interlocking structure in the joints of the lower layer, which enhanced its mechanical bonding ability with Al alloy. • Ultrasonic optimize the forming quality of aluminum/steel friction stir welding joint. • Ultrasonic refines the grain size and improves the recrystallization degree. • The morphology of hook structure is optimized under the action of ultrasonic. • Ultrasonic reduces the thickness of intermetallic compound layers. • The mechanical properties and fracture mechanism of welded joints is changed. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract High-quality aluminum /steel joint was achieved via self-riveting friction stir lap welding (SRFSLW) characterized by the prefabricated holes in steel sheet. According to the origination of filling materials, the prefabricated holes were filled with the plasticized aluminum materials in this order: the deformed aluminum ahead of a pin firstly, the stirred aluminum by the pin body secondly and the driven aluminum by the pin tip finally. The strength of the SRFSLW joint reached maximum value of 317 N/mm at the hole diameter of 3 mm, which was 23% higher than that by conventional friction stir welding (FSW). The optimized joints failed at both the aluminum/steel interface and the formed aluminum rivets. The synergistic effect of mechanical bonding induced by the riveting and metallurgical bonding induced by the Al/Fe IMC layer contributed to high strength of the SRFSLW joint. [ABSTRACT FROM AUTHOR]