Hardening behavior of Al-0.25Sc and Al-0.25Sc-0.12Zr alloys during isothermal annealing.

The hardening behavior of Al-0.25Sc and Al-0.25–0.12 (wt.%) alloys during isothermal annealing were studied by transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), and hardness measurements. The results show that Sc-containing aluminum alloy contained fine dispersion of spherical secondary Al 3 Sc particles, which developed during the annealing process. Al 3 (Sc, Zr) precipitates in the Al-0.25Sc-0.12Zr alloys are core-shell structure. Different isothermal annealing temperatures can lead to different strengthening effects on the alloys. Al-0.25Sc and Al-0.25Sc-0.12Zr alloys both exhibit obvious annealing hardening behavior, and the ternary Al-0.25Sc-0.12Zr alloy shows better thermal stability than Al-0.25Sc alloy. • The diffusion rate of Sc atoms is inhibited by Zr atoms, which can prevent the coarsening of Al 3 (Sc, Zr). • The hardness decrease in Al–Sc alloy is mainly caused by the coarsening of Al 3 Sc particle. • The radius of the Al 3 (Sc,Zr) particles can maintain their value when annealed at higher temperature (>340 °C) for longer time (∼24 h). [ABSTRACT FROM AUTHOR]