Friction stir consolidation of aluminium chips: A new approach to overcome the inhomogeneous properties of the consolidated billet

Abstract

The need to improve the recycling process of metals to achieve sustainability goals is reflected in the growing interest in solid-state recycling approaches. One of these is the Friction Stir Consolidation (FSC), able to directly transform chips into consolidated billets. The main features of this process are the pressure and the rotational speed of the tool which compresses and heats up the chips collected inside a designed die. During the consolidation process, the friction between the tool and chips surfaces plays an important role because it is the main source of heat, therefore the heat transfer starts near the tool to the bottom of the billet resulting in an inhomogeneous material property. This aspect leads to both inhomogeneous microstructure and hardness characterization of the consolidated billet. To improve the effectiveness of the friction stir consolidation recycling process, this study focused on a numerical approach by proposing a new setup in which the structure where the die and the chips are placed on, namely backing plate, was heated up aiming to activate a heat flow also from the bottom.