Microstructure, mechanical properties, and damping capacity of high-Zn-content Al–Zn–Mg alloys with Sc and Zr additions

Abstract

In this study, Al–15Zn–0.5 Mg–Sc–Zr alloys with different Sc and Zr contents were fabricated by casting, rolling, solution treatment, and aging at low and high temperatures. Primary and precipitated Al3(Sc,Zr) and Al3Zr phases could promote grain refinement in the high-Zn-content Al alloys more effectively than the Al3Sc phase, and the composition characteristics of high Zn and low Mg contents led to the Al–15Zn–0.5 Mg–Sc–Zr alloys exhibiting high thermal stability of η′ phases during aging at high temperature and long time. The Al3Sc and Al3(Sc,Zr) phases could promote the formation of fine η phases in the Al–15Zn–0.5 Mg–Sc–Zr alloys, but the Al3Zr phase could not. Finer grains and second phases led to the Al–15Zn–0.5 Mg–Sc–Zr alloys with Zr single addition and Sc, Zr collaborative additions exhibiting better mechanical properties than the alloy with Sc single addition. Meanwhile, the damping capacities of the Al–15Zn–0.5 Mg–Sc–Zr alloys with high-temperature aging were higher than those of the same alloys with aging at a low temperature due to their less numbers of dislocation pinning points and higher interface slipping ability.