Dissimilar Joining Technologies for Aluminum and Steel: Interface Regulation, Defect Suppression, and External Field Assistance

In the automotive manufacturing industry, lightweighting has emerged as a key strategy for improving energy efficiency and reducing greenhouse gas emissions. Automobile manufacturers have successively adopted the strategy of replacing steel with aluminum (Al) and using higher-strength steel (HSS) to achieve vehicle weight reduction. However, Al and steel have significant differences in thermophysical properties, which greatly increases the difficulty of joining them. Numerous studies have effectively controlled the thickness of the intermetallic compounds (IMCs) layer at the weld interface by optimizing process parameters, adding filler materials and interlayers, and applying external energy fields. Therefore, this review categorizes Al/steel joining technologies into thermal, mechanical, and composite joining. It systematically discusses and summarizes the latest research findings, current applications, and development trends for each joining method.