Enhancement Of Forming Limits Of Aluminum Alloys Using An Intermediate Heat Treatment

Since the lightweight material aluminum exhibits reduced formability compared to conventional steel grades, additional steps for extending the existing forming limits have to be conducted. This paper presents an innovative approach for heat treatment embedded between two cold forming steps. The application of such intermediate heat treatment may reduce the strain hardening of the material which was induced during a first cold forming step. The alloy discussed in detail is AlMg4, 5Mn (AA5182). The heat treatment, e.g. in a furnace, should take place at a predefined temperature for a certain duration. This allows a higher degree of deformation in the second forming operation. The advantages of this methodology can be shown by conducting tensile tests. Tensile specimens are first pre‐strained to a defined strain value and then heat treated in a way that the recrystallization of the aluminum alloy is avoided. After cooling down the samples to room temperature, further tests are conducted up to failure of the material. As a result of the experiments, stress‐strain curves dependent on the heat treatment condition are obtained. Comparing the different curves the support of the heat treatment on formability can be analyzed