Direct Recycling of Aluminium Chips into Composite Reinforced with In Situ Alumina Enrichment

Abstract

Direct hot extrusion is a sustainable technique for recycling aluminium chips into aluminium matrix composite. Reinforcement particles are used to improve the mechanical properties. In this paper, the reinforcing medium of alumina layer that forms on the chip surface were enriched in situ via thermal treatment. Three types of chips were prepared namely; non-treated, treatment of 300 °C for 60 minutes and treatment of 500 °C for 10 minutes. The chips were compacted into chip-based feedstock having a density of 75 %, 85 % and 95 %. The chip-based feedstocks were preheated at 500 °C for 3 hours before extrude. Tensile test performed on the extrudate found that variation in the types of chip and feedstock relative density has affected the ultimate tensile strength. The highest ultimate tensile strength of 256 MPa is obtained from the condition of chip treated at 300 °C for 60 minutes and a feedstock density of 85 %. Elemental analysis on the extrudates reveals that the oxygen content is increased when the extrudates made from heat treated chip. Apart from heat treatment, the oxygen content also affected by the feedstock density.