The influence of the mischmetal RE with two contents (0.82 wt.-% and 1.49 wt.-%) has been studied on the aging hardening behavior, the microstructure and the tensile properties of Al-2.3Li-2.6Cu-0.16Zr alloys at room and elevated temperature. It was indicated that the aging process was accelerated but the hardness at the peak point and the over-aged condition was decreased with RE addition after the study of the aging hardening behaviour at 160 ℃, 190 ℃ and 220 ℃ respectively. TEM analysis showed that the precipitation and promote growth of T_1 phase (Al_2CuLi) within the grains was increased and the volume fraction of T_1 decreased, on which the effect of RE was discussed. However, there was no influence of RE on the precipitation and promote growth of δ' phase. The RE-contained alloys have a slight increase in strength and a slight decrease in plastics at the peak aging state. The overweight RE content has no effect on the plastics but decreases the strength. The SEM observation shows that the tensile fracture surface will change from the transgranular with delamination first to the transgranular with intergranular then to the transgranular completely as the increasing RE content. The dependence of the tensile properties of the alloy with RE on temperature is almost the same as that without RE. The elongation ratio is inhanced obviously with RE content above 220 ℃, which is considered mainly by the scattered T_1 phase in the RE-contained alloys.
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