Dissimilar metal welding, due to its unique combination of properties and lightweight advantages, is increasingly applied in aerospace, automotive, nuclear energy, and other fields. However, one of its core technical challenges lies in the uncontrolled formation of intermetallic compounds (IMCs) at the weld interface. These IMCs, such as FeAl, Fe3Al in the Fe-Al system, and CuAl2, Cu9Al4 in the Cu-Al system, typically exhibit high brittleness and poor ductility. Their thickness, morphology, and distribution pose a severe threat to the mechanical properties of welded joints, particularly tensile strength, ductility, and fatigue life. Excessive growth of the IMC layer or the formation of discontinuous brittle layers often serves as preferential paths for crack initiation and propagation, leading to premature joint failure.
Currently, there are widespread bottlenecks in IMC inhibition technologies for dissimilar metal welding globally. Traditional fusion welding methods, such as arc welding and laser welding, struggle to precisely control IMC growth due to rapid element mixing and solidification in the weld pool. Solid-state welding techniques, such as Friction Stir Welding (FSW) and Diffusion Bonding, can mitigate IMC formation to some extent by reducing heat input or avoiding melting, but cannot completely eliminate it. They also demand extremely high requirements for material compatibility, equipment investment, and process parameter control. In terms of technological comparison, developed countries like those in Europe, America, and Japan have accumulated extensive experience in high-energy beam welding technologies such as laser welding and electron beam welding, as well as their hybrid applications with solid-state welding, leading in precise heat source control and interface reaction kinetics modeling. China has made significant progress in dissimilar metal welding, particularly in joining high-strength steel with aluminum alloys, and copper with aluminum alloys, which has been successfully applied in some industrial products. However, there is still a gap compared to international advanced levels in fundamental theoretical research, especially concerning interface atomic diffusion mechanisms, IMC growth kinetics, and multi-scale simulation prediction. For instance, in Fe-Al welding, how to effectively control the formation of the brittle FeAl3 phase and promote the formation of tougher FeAl or Fe3Al phases remains a research hot topic. For Cu-Al welding, inhibiting the formation of brittle phases like CuAl2 while ensuring sufficient bonding strength is a critical challenge.
Recent research advancements primarily focus on several aspects: Firstly, interface modification techniques, which involve pre-placing an interlayer (such as nickel, titanium, or other high-melting-point metals with good mutual solubility with the base metals) at the dissimilar metal interface. These interlayers act as physical or chemical barriers to hinder or alter the growth path of IMCs. For example, introducing a nickel interlayer in steel-aluminum welding can effectively suppress the formation of brittle FeAl3. Secondly, novel welding processes, such as ultrasonic-assisted welding, magnetic pulse welding, and Cold Metal Transfer (CMT) welding, optimize interface reactions by precisely controlling heat input, cooling rates, and mechanical stirring. For instance, CMT welding significantly reduces the IMC thickness in aluminum-steel joints through low heat input and short-circuit transfer. Thirdly, the application of numerical simulation and artificial intelligence, utilizing first-principles calculations, phase-field simulations, and machine learning algorithms to predict IMC formation tendencies, growth rates, and mechanical properties, thereby guiding process optimization and material design. For example, CALPHAD methods are used to predict phase diagrams and diffusion behavior in multi-component systems, providing theoretical basis for interlayer material selection. Future technological breakthroughs may lie in multi-field coupled welding technologies (e.g., electromagnetic field-assisted laser welding), achieving in-situ control over interface atomic diffusion and IMC growth through precise regulation of external energy fields; and the application of additive manufacturing technologies in dissimilar metal joining, constructing gradient structures or functionally graded materials layer by layer, fundamentally addressing interface brittleness issues.
Effective inhibition of IMCs in dissimilar metal welding has profound implications for the entire welding industry. Firstly, it will greatly expand the application range of dissimilar material combinations, promoting the development of lightweight, high-performance structural components, thereby reducing energy consumption and enhancing product competitiveness. In the automotive industry, for example, the maturity of aluminum alloy body-to-high-strength steel joining technology will accelerate the lightweighting of electric vehicles, increasing their range. In aerospace, reliable joining of titanium alloys to aluminum alloys will offer more possibilities for the design of new-generation aircraft. Secondly, relevant enterprises will benefit from market opportunities brought by technological upgrades. For instance, welding equipment manufacturers will need to develop smarter, more precise welding systems; material suppliers will focus on developing new interlayer materials or functionally graded materials; and engineering service companies will provide more specialized dissimilar metal welding solutions. Currently, international companies like Trumpf in Germany and Lincoln Electric in the United States, as well as Chinese enterprises such as CRRC Group and Baowu Steel, are actively investing in R&D. The future development trend will be intelligent, green, and integrated. Intelligence will be reflected in real-time monitoring, defect prediction, and adaptive control of the welding process; green will emphasize low-energy consumption and low-pollution welding processes; and integration will refer to the deep fusion of welding technology with materials science, information technology, and artificial intelligence, forming integrated solutions.
For engineers, a deep understanding of dissimilar metal interface metallurgical reaction kinetics and thermodynamics is crucial. It is recommended that engineers strengthen their knowledge of phase diagram theory, diffusion theory, and solidification theory, and combine it with practical applications to grasp the influence of different welding processes on IMC formation. In process development, priority should be given to low heat input, rapid cooling, or solid-state welding technologies, and actively explore the application of interlayer materials. For enterprises, it is advisable to increase investment in fundamental research and cutting-edge technologies, establish close industry-university-research cooperation with universities and research institutions to collectively overcome the challenges of IMC inhibition. Simultaneously, a comprehensive welding process database and quality control system should be established, utilizing big data and artificial intelligence technologies to optimize and predict welding processes, thereby improving product quality and production efficiency. Furthermore, actively participating in international technical exchange and cooperation, and introducing and absorbing advanced technologies, are also important ways to enhance competitiveness.