CASTING ALUMINUM-LITHIUM ALLOYS IN OPEN ATMOSPHERE

The increasing need for lightweight and cost-effective materials for structural applications has resulted in significant improvements and development of new aluminum alloys for structural applications. Lithium addition to aluminum has the potential for providing a class of high strength alloys with exceptional properties suitable for weight-critical and stiffness-critical applications. Casting of aluminum-lithium alloys presents a variety of problems and high-quality ingots are not readily obtainable through conventional procedures. The reactive nature of lithium necessitates the need for inert gas treatments in order to ensure melts of acceptable quality. Exploitation of the properties of these alloys is possible only if the alloys could be cast in an open atmosphere using conventional casting techniques. This paper describes a method for casting binary and ternary aluminum-3% lithium ingots. The alloys were cast using conventional techniques in an open atmosphere under salt flux. The melting procedure and casting technique are highlighted and the intricate characteristics of the castings are discussed. The mechanical properties of the heat treated and aged castings are also examined so as to provide a basis for understanding the quality of the cast ingots.