A Study on Al/Cu Bimetal Production by Lost Foam Casting

Abstract

Abstract A356 aluminium alloy/commercially pure (CP) copper bimetal was produced via liquid-solid process by lost foam casting (LFC) technique. Cu rod was placed into an expanded polystyrene (EPS) pattern followed by applying thermoplastic adhesive to cover apertures between rod and foam, pattern coating, drying and moulding in a steel flask using free silica sand. Molten A356 alloy was poured into moulded pattern at 760 °C and 790 °C, respectively. Also, hot dip A356 coating was implemented on Cu rods for each casting temperature and the effect of pre-coating on the final product was studied. Optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and hardness devices were used to determine microstructural evaluation and interface features. No metallurgical bonding occurred between Al and both coated and uncoated Cu rods at 760 °C. However, better mechanical bonding was observed comparing to uncoated sample cast at 790 °C because Cu rod surface was started to deteriorate with increasing casting temperature. Under favour of hot dip coating, uniform and continuous interface was obtained at 790 °C. θ-Al2Cu and h2-AlCu formations were determined at the interface according to XRD and EDS results. Interface hardnesses were measured as 422 HV0.01 for θ-Al2Cu and 697 HV0.01 for h2-AlCu phases.