Dissimilar JointsIt is sometimes necessary to join aluminium or aluminium alloys to other metals or alloys; these are commonly referred to as dissimilar joints. It is not easy to weld aluminium to other metals and alloys using a fusion welding process. This is partly due to the differences in melting points and because metallurgical reactions between molten aluminium and other metals produce intermetallics and undesirable microstructures leading to cracking, porosity and other problems. Arc welding of aluminium to steel and copper has been attempted using elaborate buttering or similar techniques but good, strong, welded joints are not obtained. Joining aluminium to other alloys is normally carried out by non-fusion techniques such as soldering, brazing, friction welding, diffusion bonding and explosion cladding. Friction welding has been used successfully to weld aluminium to copper, steel, and stainless steel. No consumables are required and minimal alloy mixing takes place. When aluminium has to be joined to other materials it is most frequently achieved by use of mechanical methods such as bolts, or by adhesives.
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