Influence of Process Parameter on Microstructure, Residual Stress, Microhardness and Porosity of AA-6063 Microwave Cast

In contrast to conventional casting, casting using in situ microwave route is an advanced and promising technique of bulk metal casting wherein bulk metal is heated and melted in microwave radiations at 2.45 GHz. In this present work, AA-6063 is used as a charge material at three microwave powers of 600 W, 750 W and 900 W. The process uses three susceptor materials—stone charcoal, wood charcoal and SiC—and solidification is done at two levels as closed and open cavity. The optimization of the process parameters has been done through Taguchi technique. Microstructure and microindentation hardness studies of the developed casts divulged that smaller equiaxed grains could be obtained in densely cast samples 15 and 9. In these cast samples, the presence of intermetallic phases of Al2Mg3, MgZn2, Mg2Si, Al2Mg was observed; however, the cast sample 18 contains intermetallic phases of Al2Mg, MgZn and Al2Mg3. It was found from this work that the grain structure and intermetallic precipitates in the developed cast depend primarily on solidification environment, microwave power and susceptors. Microindentation hardness of the cast sample 18 in the present study was about 166 HV that is higher than the other developed casts. The characterization of developed casts in terms of microstructure, elemental analysis, porosity, XRD and fractography is analyzed. The results reveal that the rapid solidification and increased microwave power alter elemental composition, distribution and size of eutectic phases resulting in increase in the microindentation hardness.