How is Aluminum welded to Stainless Steel?
It must be realized that fusion welding is generally not suitable for welding together dissimilar materials like aluminum and stainless steels. That is because of widely different melting temperatures, no mutual solubility in molten state, and because of differences in thermal conductivity and in thermal expansion that cause stresses and cracks. During welding, low temperature melting phases and several brittle intermetallic phases are generated that compromise the integrity of the weld. Also not every aluminum type and not every stainless steel type can be considered for being joined together. However a highly localized fusion welding process of elevated power density like Electron Beam Welding in vacuum may be sometimes used, provided that a third transition metal, compatible with both base metals, is used in between. In the specific case Silver might be used as a transition element, or to bridge the gap. Solid state welding is applicable in certain combinations, providing acceptable
