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Inspired by steel forming strategies, this study focuses on the effect of differential cooling on mechanical properties and precipitation kinetics during hot stamping of high strength AA7075 alloy. For this aim, different forming strategies were performed using segmented and differentially heated forming tools to provide locally tailored microstructures. Upon processing, uniaxial tensile tests and hardness measurements were used to characterize the mechanical properties after the aging treatment. Microstructure investigations were conducted to examine the strengthening mechanisms using the electron channeling contrast imaging (ECCI) technique in a scanning electron microscope (SEM). Based on the obtained results, it can be deduced that the tool temperatures play a key role in influencing the mechanical properties. Lower tool temperatures result in higher material strength and higher tool temperatures in lower mechanical properties. By changing the cooling rate with the use of differently heated forming tools, the mechanical properties can be controlled. Microstructure investigations revealed the formation of very fine and homogeneously distributed particles at cooled zones, which were associated with elevated mechanical properties due to the suppression of second phase particle formation during cooling. In contrast, coarse particles were observed at lower cooling rates, explaining the lower material strength found in these zones.

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The recently increasing demand for hot stamped aluminum components in the automotive and aerospace industries explains the necessity of designing efficient and resource-conserving thermo-mechanical processes. Within the thermo-mechanical process, the simultaneous effect of deformation and temperature accelerate the precipitation kinetics. Therefore, this study focuses on the combined effect of forming and aging processes on the mechanical properties of high-strength aluminum alloys AA6082 and AA7075. For this aim, two different thermo-mechanical aging process strategies after solution heat treatment and quenching in a water-dilutable polymer quenchant are proposed. The superpositioning of the forming step is either performed at the beginning or continuously during the aging treatment. The resulting mechanical properties are characterized using tensile tests. With increasing the plastic elongation, there is an increase in yield and tensile strength, which is accompanied by a significant decrease in strain after failure. Both thermo-mechanical aging strategies reveal mechanical properties similar to the conventional T6 peak aged condition with a significant reduction in process time from 24 h to 5 h.

The present study focused on the influence of different aging conditions on the strain-dependent damping of the high-strength aluminum alloy AA7075. For this purpose, different artificial aging strategies were carried out after solution heat treatment with subsequent water quenching to identify correlations between microstructural evolution, hardness development, and individual material damping. The resulting material damping was measured using an experimental setup based on the principle of electromagnetic feedback. Scanning transmission electron microscopy (STEM) investigations were carried out using a scanning electron microscope (SEM) to characterize the material’s microstructure. Depending on the aging conditions, the damping investigations revealed specific characteristic behaviors in the strain-dependent range from 1 × 10−7 to 0.002. Peak aging conditions showed lower damping than the overaged conditions but resulted in the highest hardness. The hardness decreased with increasing aging time or temperature.