The use of post-weld temper pulses to control failure modes of dissimilar advanced high strength steel stack ups in resistance spot welded

A common strategy to reduce GHG emissions from the transportation sector is vehicle light weighting, such as through the use of advanced and/or lightweight structural alloys such as advanced high strength steels (AHSS). Modern vehicles are assembled from components fabricated from different materials, with many of these components needing to be welded together, which can be challenging if the materials have substantially different compositions or mechanical properties. In this presentation, results from resistance spot welding trials of a dissimilar AHSS stack-ups will be presented. First, the development of the weldability lobe will be presented, elucidating the effect of weld current on nugget diameter, expulsion, and failure mode. Subsequently, the effect of using post-weld tempering pulses on changing the failure mode and peak load capacity of the joint will be examined. Microstructure analysis along with high resolution micro- and nano-hardness measurements at key locations throughout the joint will be presented to explain the observed mechanical and fracture properties of the joints.