Molten metal of a first composition is fed into a mold cavity, via a first control apparatus, wherein the control apparatus is open, wherein the feeding includes at least flowing out of a first feed chamber. The first control apparatus is closed. A second control apparatus is opened. Molten metal of a second composition is fed into the mold cavity, via the second control apparatus, wherein at least a portion of the metal of the first composition in the mold cavity is sufficiently molten so that an initial feed of molten metal of the second composition mixes with the molten metal of the first composition in the mold cavity, wherein the feeding includes at least flowing out of a second feed chamber, wherein the second composition is different from the first composition. An ingot is removed from the mold cavity, wherein the ingot as a top section, a middle section, and a bottom section, wherein the bottom section is composed of metal of the first composition, wherein the top section is composed of metal of the second composition, wherein the middle section is composed of a mixture of metal of the first composition and the second composition.