Joining zone shape optimisation for hybrid components made of aluminium-steel by geometrically adapted joining surfaces in the friction welding process

Abstract

In the Tailored Forming process chain, serially arranged aluminium-steel semi-finished products, joined by friction welding, are formed into hybrid shafts by a forward extrusion process. In the extrusion of serially arranged hybrid semi-finished products, it is crucial that the yield stress differences between the two materials are as small as possible. If the yield stress difference between the material components is too high, the local deformation is not sufficient and the different materials flow successively into the conical taper area with only a parallel displacement of the interface. In the preliminary work of the Collaborative Research Centre (CRC) 1153, the yield stress difference between the steel and aluminium alloy could not be compensated despite a developed inductive heating strategy, whereby the previously numerically determined optimised joint zone shape could not be achieved. In addition to the adapted heating strategy, the geometry of the joining zone can also be influenced by geometrically adapted joining surfaces in the friction welding process. In the context of this technical contribution, an individual adaptation of the joining zone geometry of the semi-finished products before friction welding is presented, whereby the numerically determined joining zone geometry can be achieved. With the conical welding surface geometries, an increase in bond strength of approx. 18 % was reached in contrast to plane surfaces. In addition to an extension of the joining zone surface, the relative velocity in the sample centre could also be increased, which has shown a positive effect on the bond strength.