Dissimilar Materials Joining of CFRTP and Aluminum Alloy by Resistance Spot Welding

Abstract

CFRTP (Carbon Fiber Reinforced Thermoplastics) are expected to be used for lightweight component parts in the automobile industry, due to their properties such as high specific strength and high specific stiffness. Because of their expensive cost, however, their application to mass-produced vehicles is limited and expected to be used based on the concept of multi-material combined with conventional materials such as aluminum and steel. For the adaptation of a multi-material body, joining technologies for dissimilar materials are required, and a reasonable and practical high performance joining method is expected to be developed. Resistance spot welding is the well-used method for joining panels and bodies in automobiles using metal materials. If the resistance spot welding can be used for joining dissimilar materials of CFRTP and aluminum alloy, there is no need to introduce new equipment and it promotes the adoption of CFRTP. In this study, in order to develop a resistance spot welding technology of CFRTP and aluminum alloy, the influences of current, welding time and electrode force on lap-shear strength were evaluated and the joining mechanism was clarified. In the resistance spot welding of CFRTP and aluminum, the dielectric breakdown of resin, which is a matrix of CFRTP, occurs at the initial stage of energization. After the decomposition of the resin by the high temperature with the dielectric breakdown, an electric path of carbon fibers in CFRTP was created, and direct resistant heating of the carbon fibers melts the surrounding matrix resin. Therefore, larger welding area and fracture load is obtained in the case of longer welding time, larger current and lower electrode force. The shear strength of 17.3MPa was obtained by the resistance spot welding of CFRTP and aluminum with silane coupling treatment.

Research on online intelligent welding system based on resistance spot welding of aluminum galvanized steel

“…There are cracks in the IMC layer, with an uneven distribution of thickness, and the elements are mainly Al and Fe, with the compounds FeAl 3 and Fe2Al 5 , 14–16 and trace Si, Mg, and Ag elements. Zn elements present at the outer edge of the weld core and the compounds produced by Al and Fe have lower metal bonding energy than FeAl 3 and Fe 2 Al 5 , 17–20 so the extrusion of Zn elements is conducive to improving the mechanical properties of welded joints. 21–23 Porosity and inclusion defects were present at the weld core, and in situ observation experiments of the liquid aluminum/solid steel reaction revealed that the alumina film ruptured under thermal expansion, phase change expansion, and extrusion of the electrode, and liquid aluminum flowed through the alumina film cracks and contacted with the steel, and then interfacial reactions occurred, which moved the ruptured alumina film upward, an observation that explains the formation of inclusion defects.…”

Optimisation and study of a welding process for aluminium and galvanised steel based on resistance welding

“…Resistance spot welding, as the main joining method in body construction, has great potential and relevance in realising aluminium/steel joints due to its low cost, high efficiency, high reliability, and ease of automation. [1][2][3][4][5][6] However, the metallurgical incompatibility and the great difference in physical properties between aluminium and steel, as dissimilar metals, pose difficulties in the welding process; additionally, the brittle intermetallic compound layer on the aluminium/steel weld interface degrades the mechanical properties of the joint. [7][8][9][10][11][12] The presence of a zinc layer not only significantly increases the welding current compared to that in bare plate welding of aluminium and steel, [13][14][15] but also leads to inconsistent weld quality and further degrades the mechanical properties of the joint, thus making effective metallurgical joining of zinc-coated steels and aluminium alloys a major challenge in welding processes.…”