Formability Analysis of a Local Heat-Treated Aluminium Alloy Thin-Walled Tube

Abstract

The environmental concerns to save energy are currently driving the attention toward alternative ways to produce lightweight components, matching the most promising light alloys (as in the case of aluminium alloys) with new and innovative manufacturing trends. To address these new requirements the use of tubular structures has increased as a solution to reduce weight. Parallel to the need to increase the material formability local heat treatment of metal sheets has gained some relevance in the last years. The present work is focused on the evaluation of the formability at room temperature of thin-walled aluminium alloy tubes previously overaged in specific zones by laser. The formability limits of the thin-walled tube material in the ‘as-received’ condition were preliminarily determined by means of tensile tests and tube expansion with elastomer. An initial numerical analysis was performed in order to define laser heating parameters to effectively overage the material. The experimental work (tensile and tube expansion tests) was assisted by the Digital Image Correlation (DIC). On the other hand, the laser treatment to obtain Locally Overaged Tubes (LOTs) was investigated according to the results of the preliminary numerical simulations and such LOTs were subjected to experimental tensile and tube expansion tests. The strain paths and failure strains obtained on LOTs were assessed and compared to the formability limits of the ‘as-received’ tube, thus allowing to evaluate the effect of the local modification of the material properties on the formability of the tube.