Effect of Rare-Earth Elements on the Structures and Mechanical Properties of Mg--8Li Alloys

The effect of rare earth element (RE) (Ce, La, Nd) on the structure and mechanical properties of Mg--8 mass% Li ( alpha + beta ) alloys has been investigated. RE formed intermetallic compounds with magnesium (Mg sub 17 La sub 2 , Mg sub 17 Ce sub 2 , Mg sub 12 Ce, Mg sub 3 Nd). Below 90% rolling reduction, Mg--Li--RE ternary alloys showed work hardening behavior which is similar to that of Mg--Li binary alloy, while > 90% rolling reduction they exhibited the work softening probably due to recovery. Isochronal annealing < 373K softened cold-rolled Mg--Li--RE alloys. On the other hand, the recrystallization temperature was raised by the addition of RE. Age-hardening due to the precipitation of alpha phase in beta phase was observed in all alloys. Overaging was recognized in Mg--Li binary alloy, but not in Mg--Li--RE ternary alloys. The results suggest that RE addition improves the thermal stability of precipitates, resulting in the improvement of elevated temperature strength through aging treatment. The addition of RE tended to increase the tensile strength, but to decrease the elongation.