Abstract
Abstract. Hybrid material compounds offer an extension of the technological application range of monolithic components by combining positive material-specific properties. In the case of steel and aluminium, a load-adapted component with high strength areas and a reduced weight can be created. Tailored Forming enables the joining zone created by a pre-joining process to be modified and enhanced by a subsequent forming step. Derived from previous studies, an enlarged joining zone interface through spherical joining zone curvature and an equalisation of yield stresses through an inhomogeneous induction heating with partial cooling are necessary to achieve a defect free bond with high strength and ductility. In order to further enlarge the joining zone interface and hence to increase the surface ratio of juvenile welding spots without brittle intermetallic compounds, different local plastic strains are induced. Additionally, an alternative spray cooling concept is used to evaluate the effect of steeper temperature gradients on the bond quality. Rotary friction welded specimens made of 20MnCr5 steel and EN AW-6082 aluminium are cup backward extruded with different extrusion ratios using punch diameters of 22 mm and 30 mm. Metallographic images, SEM analysis and hardness tests of cross-sections are used to evaluate the bond quality with regard to the joining zone formation, occurring defects and the resulting intermetallic compound. With cooling, higher yield stresses could be set in the aluminium, which counteract material failure even with larger punch diameters due to a higher deformability. However, the surface enlargement of the joining zone is reduced. Despite the higher surface enlargement in uncooled specimens, insufficient bonds were achieved due to existing cracks in the aluminium in or near the joining zone interface, as well as significant thicker intermetallic compounds.
Publisher
Materials Research Forum LLC