DEVELOPMENT OF ULTRA LIGHT MAGNESIUM LITHIUM ALLOYS

Magnesium-lithium alloys are among the lowest density metallic materia ls. Addition of lithium, with a relative density of 0.53, in magnesium reduces the density of the alloy significantly. Furthermore, addition of nearly 11 wt.% lithium converts hexagonal close packed structure o f pure magnesium to a body centered cubic lattice, markedly improving formability of the alloy. The development of these alloys, however, ha d been hampered dud to the high reactivity of lithium and magnesium in the molten state and also, due to poor creep resistance and instabili ty of mechanical properties at room temperature. In an attempt to indi genize these ultra light alloys for possible applications in Indian sa tellite programme, detailed research work was initiated in DMRL. The d ifficulties associated with producing sound cast ingots have been over come by controlling melting and casting parameters of these alloys. Ex tensive work has been done on structure-property correlation of alloys with varying lithium content and minor alloying additions. Based on t hese work, advanced magnesium-lithium alloys have been developed with improved tensile properties, room temperature :stability and creep res istance. Wrought products (plates/sheets) of magnesium-lithium alloy h ave been supplied to ISAC, Bangalore and are being used in their INSAT -2 programme. This paper describes the systematic studies carried out in the laboratory to indigenize these ultra light alloys.