Thermomechanical processing of AlMgSiCu alloys for high electrical and thermal conductivity applications

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Al-Mg-Si alloys (eg. 6101 and 6201 alloys) with a typical composition of 0.6-0.9%Mg and 0.5-0.9%Si, are commonly used in overhead transmission lines and other electrical engineering applications due to its high electrical conductivity and specific strength. However, the electrical conductivity is highly sensitive to alloying additions because higher magnesium and silicon contents significantly deteriorate electrical conductivity due to increased scattering of conduction electrons by solute atoms. Furthermore, there is a direct proportional relationship between electrical conductivity and thermal conductivity .Themomechanical processing involving solution heat treatment, followed by water quenching, deformation and artificial ageing has been applied to conventional Al-Mg-Si alloy to achieve good electrical conductivity and mechanical strength. Small addition of Cu to AlMgSi to form quaternary AlMgSiCu alloy has led to superior mechanical strength after thermomechanical processing route. Hence, one can explore this AlMgSiCu alloy for potential applications in the wiring systems of electric vehicles and in the cooling systems of electric vehicle battery modules to fulfil the light-weighting strategy. However, there is no information on the effect of thermomechanical processing and alloy chemistry of this type of AlMgSiCu alloy on electrical and thermal conductivity properties. The main aim of this research project is to establish a fundamental understanding of the effect of alloy chemistry and processing of AlMgSiCu alloy involving melting, extrusion, thermomechanical treatment on resultant microstructure, conductivity and mechanical properties, so as to develop the next generation of high thermal and electrical conductivity aluminium alloy for automotive applications. The processed sections will be analysed using a combination of optical/electron microscopies and eddy current method to understand the effect of composition and processing conditions on microstructure, strength and conductivity.