Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc alloys.However,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many cases.Here,using atomic-scale transmission electron microscopy and atomic-resolution spec-troscopy,we have revealed the microstructural differences between two age-hardened Al-0.5Mg-0.4Si(wt.％)alloys with and without Sc-addition.The first significant effect of Sc-addition on the precipitation microstructure of the Al-Mg-Si-Sc alloy is that Sc-atoms may distribute at the β"-precipitate/Al-matrix interface and therefore accelerate aging kinetics at the initial stage of hardening.The second significant effect of Sc-addition is that in the transition from the β"-hardened peak-age stage to the β'-hardened late stage,Sc-atoms can greatly improve the stability of transitional β"/B'/β''composite precipitates by entering the B'-substructures and/or locating at the precipitate/Al interfaces.As such Sc-atoms effectively suppress β"to β''transformation and cross-sectional coarsening of both β"and composite precipitates,leading to much finer precipitate needles with smaller diameter but much larger length,as compared with those precipitate needles formed in the alloy without Sc-addition.Hence,the alloy with Sc-addition exhibits a much better thermal stability than that without Sc.

S.B.Wang;C.F.Pan;B.Wei;X.Zheng;Y.X.Lai;J.H.Chen

Key Laboratory of LCR Materials and Devices of Yunnan Province,National Center for International Research on Photoelectric and Energy Materials,School of Materials and Energy,Yunnan University,Kunming 650091,China;Collaborative Innovation Center of Renewable Energy Materials and Department of Physics,Guangxi University,Nanning 530004,China;Center for High-Resolution Electron Microscopy,College of Materials Science and Engineering,Hunan University,Changsha 410082,China

材料科学技术（英文版）

[1]S.B.Wang;C.F.Pan;B.Wei;X.Zheng;Y.X.Lai;J.H.Chen-.Nano-phase transformation of composite precipitates in multicomponent Al-Mg-Si(-Sc)alloys)[J].材料科学技术（英文版）,2022(15):216-226

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