A novel approach to enhance mechanical properties during recycling of aluminum alloy scrap through friction stir consolidation

Abstract

Solid state recycling (SSR) is a new approach for making metals recycling more efficient with respect to remelting-based approaches. Friction stir consolidation (FSC) is a new solid-state process that is employed to recycle metallic scraps. Until now, a single-step FSC process was applied to recycled metal chips. During the single-step approach, critical processes parameters, especially processing time and rotational speed, are considered vital to control the quality and mechanical properties of the billet. However, the effectiveness of process parameters is highly restricted by challenging masses of recycling chips and machine competency. The present study first highlights the issues of the single-step FSC process, such as unconsolidated billet and poor mechanical properties at the bottom of the part, i.e., far away from the stirring action. Then, for the first time, three different two-step FSC methods were introduced as new approaches to overcome the existing challenges of the single-step method. The effectiveness of these methods was evaluated through the Vickers hardness measurements, and microstructure analysis. The results showed that two-step FSC methods successfully led to a fully consolidated billet and considerably improved mechanical properties.

Forgeability characterization of multi-material based functionally graded materials manufactured through friction stir consolidation

“…It is possible to see that hardness decreases when moving from the top to the bottom and from centre towards the outer zone of the analysed cross section. This trend derives form FSC process mechanics [7]. As a matter of fact, it is a less ductile material with respect the series 2011 and several defects occurred.…”

“…Over the last decade, solid state recycling (SSR) processes have been analysed as a viable alternative for recycling metals scraps [1]. Different variants have been proposed for recycling metal chips: direct hot extrusion [2], equal channel angular pressing (ECAP) extrusion [3], screw extrusion [4], spark plasma sintering (SPS) [5], friction stir extrusion (FSE) [6] and friction stir consolidation [7]. This process category along with high quality recycled semi-finished products, has proved its energy and resource efficiency.…”

Characterization of friction stir consolidated recycled billet by uniaxial compression tests with miniaturized cylindrical specimen

“…Finally, chips were transformed into a cylindrical billet by applying the rotating tool at 1500 rpm and 20 kN load for a processing time of 30 seconds. The selected process parameters in the current investigation were based on previous studies [13,16] as promising conditions for manufacturing sound billet. Measured outputs.…”

“…A typical FSC, due to process mechanics such as different temperatures and strain rate distribution, is characterized by variation in mechanical properties along the radial and longitudinal direction of the billet [13,14]. Previously, this variation was validated by Vickers's hardness test and grain size distribution analysis [16]. It is also crucial to analyze the effect of process mechanics on other important properties such as mechanical strength, fracture strength, and ductility.…”

Fabrication of Billet from Aluminum Alloys AA 2011-T3/7075 Chips through Friction Stir Consolidation

“…1. These process parameters were selected based on previous studies [25] that successfully led to develop a sound billet. Finally, the consolidated billet was removed from the die.…”