Within the subproject B3 of the Collaborative Research Centre 692, it has been shown that Al-Mg compounds with a good bonding quality can be produced by hydrostatic co-extrusion. The processing by die forging also showed a good formability of the compounds. However, there are some technological issues limiting the field of possible industrial applications. This lecture focuses on the most recent advances to overcome these limitations as follows.
During processing by forging, the aluminum sleeve is thinned in areas of high strains depending on the component geometry. Based on FE-simulation results an eccentric magnesium core arrangement during co-extrusion was experimentally investigated. Rods with an offset of 0.25, 0.5 and 0.75 mm were produced by eccentric hydrostatic co-extrusion. Subsequently, ultrasonic testing was used to evaluate the bonding quality across the entire rods. For the forging investigations, the basic process Rising was chosen. The still good bonding quality after forging was examined by dye penetrant testing and optical microscopy.
After cutting the forging specimens from a co-extruded rod, the magnesium at the front surfaces is unprotected. This remains even after forging. Due to a better corrosion protection, closing the front surfaces by forging was investigated. Therefore, the production process of the demonstrator “SMART-Body” was used. By adapting the heading die and a reduction of the magnesium core a fully aluminum cladded component could be produced. The closed front surfaces were examined by optical microscopy.
Regarding the process chain in general, the hydrostatic co-extrusion of Al-Mg compounds is very complex and expensive. With respect to an industrial application, the process chain should be reduced by avoiding this process. Nevertheless, to ensure the compound properties, the integration of the interface formation by diffusion into the forging process was investigated. Forging compound-specimens were produced by machining and prepared by a chemical removing of the oxide layers. After mechanical joining and heating, the specimens were forged by Rising. The interface formation was examined by optical microscopy and SEM.