Abstract
Natural aging after solution treatment has a negative effect on the precipitation strengthening of Al–Mg–Si alloys since Cluster(1) formed at a room temperature cannot be dissolved or transformed into precipitates during artificial aging at 170 °C. In this study, cold rolling is focused on as an alternative solution to pre-aging, which is a conventional method to prevent Cluster(1) formation. It is known that excess vacancies are necessary for cluster formation. Cold rolling suppresses cluster formation because excess vacancies disappear at dislocations introduced by cold rolling. In addition, it is expected that cold rolling accelerates the precipitation behavior because the diffusion of solute atoms is promoted by introduced lattice defects. The transition of Cluster(1) was evaluated by Micro Vickers hardness tests, tensile tests, electrical conductivity measurements and differential scanning calorimetry analyses. Results showed the negative effect of natural aging was almost suppressed in 10% cold-rolled samples and completely suppressed in 30% cold-rolled samples since Cluster(1) dissolved during artificial aging at 170 °C due to lowering of the temperature of Cluster(1) dissolution by cold rolling. It was found that the precipitation in cold-rolled samples was accelerated since the hardness peak of 10% cold-rolled samples appeared earlier than T6 and pre-aged samples.
Highlights
The effect of cold rolling on Cluster(1) dissolvability and formability in AlMg-Si alloy was researched by evaluating the precipitation behavior of cold-rolled samples in order to illuminate whether cold rolling is effective in preventing the negative effect of natural aging
The evaluation was done by Micro Vickers hardness tests, tensile tests, electrical conductivity measurements and differential scanning calorimetry analyses
Cold rolling suppressed the amount of Cluster(1) formation since excess vacancies disappeared at dislocations introduced by cold rolling
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. 6000 series aluminum alloys are utilized as body sheet panels. The panels are strengthened during heat treatment of the paint-baking process due to precipitation strengthening. The overall precipitation sequence of 6000 series aluminum alloys is mostly believed as follows [1,2]: Supersaturated solid solution → Clusters → β”(L) → β’(Q’) → β
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