Why are interlayers used when joining dissimilar metal combinations by friction welding?

TWI Frequently asked questions

In dissimilar metal combinations, such as different aluminium alloys welded to one another or to metals such as copper or steel, a brittle intermetallic layer can form at the weld interface. In order to minimise the formation of theseintermetallics a thin-layer of pure aluminium is used. In some circumstances, other interlayers can be used. TWI staff may be able to provide further advice in this area.

Copyright by TWI, 1999