Laser beam brazing of steel-aluminium tailored hybrid blanks

Abstract

The prerequisite for a consistent lightweight construction is the exhaustive utilization of the weight-specific characteristics of different construction materials. Therefore, multi-material-design is becoming more and more interesting to the transportation industry. However, the potential of material mixing for lightweight construction cannot be entirely exploited because of the lack of adequate joining processes. For the manufacture of Tailored Hybrid Blanks made of steel and aluminium the Laser Zentrum Hannover developed a laser brazing process. Process studies, metallographic analyses and tensile tests were carried out for connections of AA6016 sheets in combination with various steel sheet metal grades. Different zinc solders were used as filler metal. Although it is thereby possible to avoid the melting of the aluminium base metal, intermetallic FeAl-phases developed and were characterized using SEM and EDX analysis.It was thus proven that the intermetallic phases affect the mechanic characteristics of the seam. However, the weaker base metal of overlap-joints fails in tensile tests. Depending on the seam volume butt-joints show approximately 80 % of the strength of the weaker base material. By means of cupping tests a sufficient deformation capacity of the Tailored Hybrid Blanks could be demonstrated for a specific combination of materials.