Dissimilar material bonding technology for lightweight future mobility: A review

The transportation industry has played a crucial role in advancing human society, but it has also raised concerns about carbon emissions and environmental pollution. As a result, significant research is being conducted in various areas, such as electric vehicles, powertrain energy efficiency, shared mobility, and autonomous driving. However, vehicles remain essential, and reducing their energy consumption is vital. One effective way to achieve this is by light-weighting vehicle materials. In the past, steel was the primary material used, but the transition to materials like aluminum has shown better weight-to-strength ratios. To drive change, we must explore the use of diverse materials since no single material is perfect. By combining specific materials, we can complement their weaknesses and enhance their strengths, opening up new possibilities for the future of mobility. One critical factor in advancing future mobility is the joining of dissimilar materials. This paper delves into various methods of joining dissimilar materials, their characteristics, and techniques to improve their joining performance. The joint strength for each joining method is also summarized in this study. The joining methods are primarily divided into mechanical joining, chemical joining using adhesives, and thermal fusion welding. Methods to enhance the joint include combining each joining method and improving surface interactions through surface treatments. The joint exhibiting the highest strength was the laser-welded joint of strength 312 MPa between Ti3Al-Nb alloy and Ni-based superalloy, while the lightest and strong joint was the friction stir-welded joint of strength 63.4 MPa in Polyamide 6 GFRP. Welded joints of polymer materials appear promising for the future mobility industry, particularly in terms of being lightweight. Additionally, there is a need to develop new methods to measure strength as the units used to represent the physical characteristics of the joints are not standardized. Some joints suffer from issues due to unclear joint area, highlighting the necessity to develop new strength measurement methods for future advancements.