Abstract
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.
基金项目
国家自然科学基金(52061003)
国家自然科学基金(U20A20274)
国家自然科学基金(51661003)
广西自然科学基金(2018GXNSFAA050012)
Science and Technology Major Project of Guangxi(AA17204036-1)
Guangxi Key Laboratory of Processing for Non-ferrous Metallic and Featured Materials(GXYSYF1803)
维普
万方数据