Yield Strength Improvement of an Al-6063 Alloy by Applying a Novel Combination of Cold Working and Heat Treatments for Die Casting of Plastic Parts

Abstract

In this work, a novel combination of designed heat treatments and cold work performed on Al-6063 alloy was proposed. The consumption of aluminium and its alloys in the automotive and aeronautic industries has increased over the past few years, in the same way, as the consumption of material for manufacturing moulds for casting of plastic parts and dies for plastics and metals. Then, it is important to find a low-cost alternative to maximise the mechanical properties of aluminium, with a negligible effect on the ductility of the alloy, which is important due to thermal and mechanical fatigue on mould and dies. It is well known that precipitation hardening increases the mechanical and yield strength of aluminium alloys with a major ductility loss. However, the developed methodology consists of a solution heat treatment, followed by cold working (strain hardening), and lastly a heat treatment (precipitation hardening and stress reliever) to produce Al 6063 aluminium alloys with enhanced mechanical strength and with a negligible ductility loss. The proposed methodology increases around 23.45% of the tensile and yield strength, with a ductility reduction of less than 1.5% in the elastic materials region. The experimental tensile testing results are correlated with nanoindentation experimental results in order to confirm that the level of cold working is directly proportional to mechanical strength levels by two different characterisation techniques at a macro- and nanoscales, respectively.