Challenges in Compound Forging of Steel-Aluminum Parts

In times of increasing energy costs automotive lightweight construction is gaining in importance. This paper deals with the production of hybrid steel-aluminum compounds by forging. The compound forging process is a promising method to successfully manufacture functional parts by applying resource-saving process steps. Nevertheless, challenges resulting from different material properties must be solved. The heating of hybrid material work pieces made of steel and aluminum is a great challenge. Steel is forged at a temperature of at least T-St = 900 degrees C, while aluminum should not exceed a temperature of T-Al = 500 degrees C. For achieving the required temperature gradient extensive experimental investigations have been carried out. Intermetallic phases form during the manufacturing process and can influence the bonding and the global part quality. In addition, methods for the characterization of the joining zone between the materials steel and aluminum are analyzed and the factors influencing the formation of intermetallic phases are determined experimentally.