Multi-physics simulation of in situ microwave casting of 7039 Al alloy inside different applicators and cast microstructure

Abstract

In the present study, finite element models of three different applicators (A1, A2, and A3) having different power densities were developed to study melting of the charge and solidification of the melt during in situ microwave casting. Multi-physics simulations were carried out to understand the effect of applicator specific processing conditions on the distribution of electric field inside the cavities at 2.45 GHz for Al 7039 alloy as charge. The alloy was cast inside the selected applicators and the mold temperature was monitored. The experimental results showed reasonable agreement with the simulation data. Simulation results revealed that the distribution of electromagnetic field inside A3 offers the lowest melting time of the charge (141% less than A1); however, it also caused the highest preheating of the graphite mold with respect to A1 (30% higher) and A2 (25% higher). It was found that the applicator-specific solidification conditions affect grain structure, intermetallic precipitation, and their distribution inside the casts. Coarser intermetallic phases (57 µm) and grains (97 ± 54 µm) were present in the Cast 3 developed using A3 due to higher preheating of the mold and slower cooling rate of the melt as compared to that in A1 and A2.