The melting processes in AK6 industrial aluminum alloy samples in the cast and homogenized conditions have been investigated by the thermal analysis with the subsequent numerical differentiation in time of heating curves in a range of temperatures from 300 to 670 °C. Temperatures of non-equilibrium solidus, equilibrium solidus, and liquidus are established. The microstructure of cast and homogenized alloy samples is studied and the local chemical composition of aluminum matrix and phases is determined.