Microalloying addition plays a significant role in controlling the characteristics of precipitates in Al alloys.This study investigates the effects of Ag and Sc microalloying addition on the thermal stability of Al–Z...Microalloying addition plays a significant role in controlling the characteristics of precipitates in Al alloys.This study investigates the effects of Ag and Sc microalloying addition on the thermal stability of Al–Zn–Mg–Cu alloys,via differential scanning calorimetry,transmission electron microscopy,and atom-probe tomography.The results demonstrate that Ag and Sc additions increase the number density ofη-MgZn_(2) type nano-precipitates(formed during heat treatment)by forming direct(Mg–Ag phase,prototype of precipitate)or indirect precursors(Al_(2) Sc phase,constituent of precipitate)for the precipitate.In addition,the Ag and Sc elements can effectively prevent the coarsening ofηprecipitates and facilitate the high-density distribution of fineηprecipitates,during the over-aging period,improving the thermal stability of the Al–Zn–Mg–Cu alloys.The thermal stability is particularly improved by Ag addition because Ag atoms directly prevent the coarsening ofηprecipitates by hindering Zn diffusion into the precipitate.On the contrary,Sc addition indirectly prevents the coarsening ofηprecipitates by depleting the solute species from the Al matrix,enabling abundant precipitates limited growth.Thus Ag addition improves precipitation strengthening by preventing the coarsening of precipitates during over-aging.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.NRF-2021M3H4A1A04091999).
文摘Microalloying addition plays a significant role in controlling the characteristics of precipitates in Al alloys.This study investigates the effects of Ag and Sc microalloying addition on the thermal stability of Al–Zn–Mg–Cu alloys,via differential scanning calorimetry,transmission electron microscopy,and atom-probe tomography.The results demonstrate that Ag and Sc additions increase the number density ofη-MgZn_(2) type nano-precipitates(formed during heat treatment)by forming direct(Mg–Ag phase,prototype of precipitate)or indirect precursors(Al_(2) Sc phase,constituent of precipitate)for the precipitate.In addition,the Ag and Sc elements can effectively prevent the coarsening ofηprecipitates and facilitate the high-density distribution of fineηprecipitates,during the over-aging period,improving the thermal stability of the Al–Zn–Mg–Cu alloys.The thermal stability is particularly improved by Ag addition because Ag atoms directly prevent the coarsening ofηprecipitates by hindering Zn diffusion into the precipitate.On the contrary,Sc addition indirectly prevents the coarsening ofηprecipitates by depleting the solute species from the Al matrix,enabling abundant precipitates limited growth.Thus Ag addition improves precipitation strengthening by preventing the coarsening of precipitates during over-aging.
