A generalized parametric model for the bonding occurrence prediction in friction stir consolidation of aluminum alloys chips

Over the last years solid state processing has been applied as an environmentally friendly recycling method for metal scrap. These approaches, by skipping the melting step, allow substantial energy and resource savings with respect to conventional remelting routes. Specifically, several processes relying on solid bonding phenomenon have been applied to recycle aluminum alloys chips. In this paper, the Friction Stir Consolidation recycling process is considered as solid-state recycling approach to turn chips of three different aluminum alloys namely AA2024, AA6082 and AA5083, into consolidated billet. The paper aims both at validating a new solid bonding criteria specifically designed for Friction Stir Consolidation as well as at proposing a general model to characterize the bonding criterion for each single considered material. In this regard, a correlation analysis and a new parametric model has been developed aiming to understand which material properties were involved in solid bonding occurrence and to predict the bonding limit curve vs temperature by means of material thermo-mechanical properties. The identified criterion and parametric model have been validated by implementing these on the bonding prediction occurrence in Friction Stir Consolidation of AA5083 aluminum chips. Results revealed that just on the basis of some mechanical and thermal properties of the material to be recycled it is possible to identify the threshold for the actual bonding of the material at different temperature levels and, therefore, properly design the recycling process by means of numerical simulation implementation.