Effect of input microwave power and insulation on microstructure and tensile properties of cast Al 7039 alloy produced at 2.45 GHz

In the present work, microwave energy was used for casting Al 7039 alloy at 2.45 GHz in the ambient cavity environment. Effects of input power and insulation of the mould assembly during irradiation on charge melting and mould preheating were studied. Five different casts were produced at 1000 W, 1200 W, 1400 W, 1400 W with an insulated pouring basin and 1400 W with insulated mould assembly. Melting time of the charge was the least while using 1400 W with insulated mould assembly, whereas preheating of the mould was observed minimum during casting at 1400 W inside an insulated pouring basin. Cast microstructures revealed that less preheating of the mould resulted in finer grains and intermetallics, which improve tensile properties of the cast. Fractographic analyses showed the presence of coarse intermetallics in the casts produced with insulated mould assembly, which resulted in significant reduction of tensile properties.