Friction welding of aluminium alloy 6061 to stainless steel 304

Friction welding is a solid state welding process, in which joining occurs at a temperature below the melting point of the work metal. Friction welding (FRW) is a process in which the heat for welding is produced by direct conversion of mechanical energy to thermal energy at the interface of the work pieces without the application of electrical energy or heat from other sources to the work pieces. Friction welds are made by holding a nonrotating work piece in contact with a rotating work piece under constant or gradually increasing pressure until the interface reaches welding temperature and then stopping the rotation to complete the weld. Welding occurs under the influence of pressure that is applied while the heated zone is in the plastic temperature range. Friction welding can be used to join a wide range of similar and dissimilar metals, and many of the dissimilar metal combinations that cannot be joined by conventional fusion welding techniques are readily joined by FRW methods. It is difficult to weld aluminium alloy 6061 to stainless steel 304 with high joining efficiencies. However by friction welding a suitable metal to stainless steel and machining the same to a thickness of around 1 mm to serve as an interlayer, the aluminium alloy 6061 can be joined to SS 304 with high joint efficiencies. Studies on joints of these combinations have not been reported. An effort was made to investigate the feasibility of friction welding of Al 6061 to SS 304 with copper as the interlayer. Studies were aimed to obtain relevant fundamental data to determine their weldability, weld interface, intermetallic compounds and fracture modes. Initial experiments have yielded encouraging results. (author)