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The aging feature of Al-Li-Cu-Mg-Zr alloy containing Sc
Authors:Tan Cheng-yu  Zheng Zi-qiao  Xia Chang-qing and Liang Ying
Affiliation:(1) Department of Materials Science and Engineering, Central South University of Technology, 410083 Changsha, China
Abstract:The aging behaviors of Al-1.42% Li-2.41% Cu-0.93% Mg-0.073% Zr-0.17% Sc (mass fraction, the same below) alloy at room temperature, 160 °C, and 160°C after 8% pre-deformation were studied respectively by hardness measurement. The microstructure of the alloy in various aging conditions was observed by TEM. The results show that the main precipitations of the alloy in quenching condition are the particles containing Sc and Zr which have certain coherent relation with the matrix. Addition of Sc in Al-Li-Cu-Mg-Zr alloy will be favorable to promoting precipitation. The particles can serve as preferred nucleation sites for δ′ phases which accelerate the aging hardening rate at initial aging. The main hardening phases of the alloy aged at 160 °C are δ′ and δ′/β′ composite precipitates. The size of the composite precipitates is very small (nanometer size). The composite precipitates will preclude efficiently the formation concentrative slip location and will improve the mechanical properties of the alloy. S′ phase will occur in the alloy aged at 160 °C after 8% pre-deformation. It is found that 8% pre-deformation has no obvious influence on the precipitation of the composite phase. Foundation item: The Key Program of the 9th Five-year Plan of China (No. 95-YS-001) Biography of the first author: TAN Cheng-yu, associate professor, born in 1963, majoring in materials and their suface performances.
Keywords:Al-Li alloy  aging behavior  composite phase
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