Product Code: ICAL07_1006

Laser Beam Aluminum-Steel Joints – Mechanical and Dynamical Properties and Detailed Microstructural Analysis of Intermetallic FeAl-Phases
Authors:
Holger Laukant, Metals and Alloys, University of Bayreuth; Bayreuth Germany
Elisa Guimaraens, Metals and Alloys, University of Bayreuth; Bayreuth Germany
Uwe Glatzel, Metals and Alloys, University of Bayreuth; Bayreuth Germany
Presented at ICALEO 2007

Mixed-materials are important in the automotive industry due to their weight saving potential and good ratio between costs and mass production. Aluminium and steel are difficult to join thermally due to the formation of intermetallic phases and differences in thermal expansion coefficients. Therefore the localized heat input of a laser beam is favourable. We present a laser weld-brazing technique for joining aluminium sheets (5XXX and 6XXX) with zinc-coated automotive steel sheets (DC04 and DX56). The process is divided into welding of the aluminium sheet and flux-less brazing of the steel sheet and can be improved by using a Nd:YAG dual-spot laser beam to promote the wetting behaviour of the braze. Mechanical as well as dynamical tests and microhardness distributions of the mixed-materials joints will be presented. Due to the differences in electrochemical potentials of iron, aluminium and zinc the corrosion behaviour of the joints within salt spray tests was investigated. The intermetallic FeAl-phases forming in the contact area of the brazed seam to the steel sheet are analysed by means of SEM, focused ion-beam and TEM. Since their high hardness and brittleness can have a strong effect on the mechanical behaviour and reliability of aluminium-steel joints the microhardness of the intermetallic phases was determined as well.