Patent ID: 8448690

Claim:
A method of casting metal, comprising the following steps: feeding molten metal of a first composition into a mold cavity, via a first control apparatus, wherein the molten metal of the first composition is an aluminum alloy, wherein the control apparatus is open, wherein the feeding comprises flowing out of a first feed chamber; closing the first control apparatus; opening a second control apparatus; feeding molten metal of a second composition into the mold cavity, via the second control apparatus, wherein the molten metal of the second composition is an aluminum alloy, 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 comprises flowing out of a second feed chamber, wherein the second composition is different from the first composition; and removing an ingot from the mold cavity after the molten metal solidifies, wherein the solidification front remained substantially planar, wherein the ingot has 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, and wherein no oxide layer exists between the sections of the ingot.