In metallurgical terms, there are two temperatures that describe the melting behavior. The Liquidus temperature is the temperature at which the alloy is 100% liquid, which is 655 C (1211 F) for alloy 6063. The Solidus temperature is the temperature at which the alloy is 100% solid, which is 615 C (1139 F) for alloy 6063. In between these two temperatures, the alloy is part solid and part liquid.