The effect of the content (0.1 and 0.5wt%) of rare earth el. ement Y on cast microstructure, aging precipitation behaviour, age-hardening response, oxidation resistance, and tensile properties at ambient and elevated temperatures for Al-Li-Cu-Mg-Zr alloy has been studied in this paper. Experimental results show that an addition of Y can refine the grain size; obviously accelerate the age-hardening process at 463K; result in the aging peak occuring early and abtain higher hardness at low temperature. During aging, the nucleation of δ'-phase and homogeneous distribution of S'-phase are promoted by the addition of Y. The recrystallization of the alloy is restrained because of the increase of β'-phase caused by Y addition. Tensile tests at ambient temperature indicate that higher ductility can be obtained by 0.1wt% Y addition and the strength does not reduce, whereas, the alloy containing 0.5wt% Y exhibits higher strength, and its ductulity does not decrease. The alloys with 0.1 or 0.5wt% Y show shear-type transgranular fracture with dimples after solution treatment. The fracture mode is a mixture of ductile intergranular and transgranular fracture inpeak-aged condition, however, when 0.5wt% Y is added, the fracture of the alloy remains shear-type transgranular. As the test temperature increases, the tensile strength of the alloys decreases with dimples after solution treatment. The fracture mode is a mixture of ductile intergranular and transgranular fracture inpeak-aged condition, however, when 0.5wt% Y is added, the fracture of the alloy remains shear-type transgranular. As the test temperature increases, the tensile strength of the alloys decreases with improvement of elongation, the alloys exhibit ductile dimple failure mode at 573K. Addition of 0.1wt% Y to the alloy leads to a significant improvement tensile properties at elevated temperature. Moreover, Y addition improves the oxidation resistance of the alloys. In the present paper, the mechenism of the effect of Y on precipitation and growth of strengthing phase as well as the relation between microstructure and properties of alloys has also been discussed.
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