Effect of Room-Temperature Pre-rolling and Pre-cryorolling on Natural Aging and Bake Hardening Response of an Al–Mg–Si Alloy

The auto industry makes extensive use of Al–Mg–Si alloys. This study investigated the effect of pre-cryorolling and room-temperature pre-rolling on the natural aging and bake hardening response of Al–0.92Mg–0.48Si alloy. The mechanical properties were analyzed using microhardness, tensile, and Erichsen cupping test. Optical microscope, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry were used to examine the microstructure of samples. The molecular dynamics simulation was also employed to study the dislocation evolution in samples deformed at room and cryogenic temperature. The results show that both room-temperature pre-rolling and pre-cryorolling introduced immediately after solid solution treatment can effectively inhibit the adverse effects of natural aging, and promote the precipitation of strengthening phase during paint baking, leading to an improved bake hardening response. Compared with the room-temperature pre-rolling, pre-cryorolling can further improve the bake hardening response because of higher dislocation density. The results of this study indicate that pre-cryorolling with a reduction of 15 pct is the most appropriate pre-deformation procedure for this alloy, both in terms of formability and bake hardening response.