The Need

Resistance welding is used to combine two metals at one point. This technique is used extensively in automotive manufacturing, combining an aluminum (Al) to an advanced high strength steel (AHSS) structure. Welding Al and AHSS together directly, however, does not create a high-quality bond, due to Al and AHSS having different melting points and chemical makeups. A thick and brittle intermetallic compound (IMC) layer can form when the Al and AHSS are combined in this manner. The IMC layer, if not controlled, deteriorates the weld's load-bearing capacity. As the automotive industry continues to move toward joining Al and AHSS, there must be an efficient way to form a high strength bond between the two metals that avoids these brittle intermetallic zones and provides the desired mechanical properties.

The Technology

Researchers at The Ohio State University have invented a process of applying a Cr-rich interlayer (such as pure Cr, electroplated Cr coating, ferritic stainless steels, and Cr containing structural C-steels) between the Al alloy and steel plates to make a much stronger bound, before resistance spot welding and other joining processes. The Cr interlayer has been shown to preclude or reduce the formation of brittle IMC interlayer. This invention expands the joining processes parameter window and dramatically improves the joint strength ductility, and toughness of the bound.

Commercial Applications

• Automotive Manufacturing

• Aerospace manufacturing

• Armored vehicles

• Ship structures

• Heat exchangers

• Pipeline industry

Benefits/Advantages

• Stronger bond between Al and steel

• Increase processing window

• Minimal modification of the well-established RSW technique

• Interlayer materials widely available to industry

• Applicable for different steel/aluminum alloys

Research Interest

The Ohio State Welding Engineering department continues to have a significant impact on innovation, competitiveness, and the sustainability of fabrication, welding, and additive manufacturing. The industry faces the dual challenge of introducing new materials into products of the future and assuring that current materials meet performance requirements. Both challenges require a better fundamental knowledge of materials joining and additive manufacturing. This requires a multidisciplinary approach that occurs at the intersection of the joining and manufacturing processes and the materials' reaction to its environment. Aspects of manufacturing and joining processes, materials science, and structural design must be considered in this multi-disciplinary approach.