Effect of Cr and Yb additions on microstructure and properties of low copper Al–Zn–Mg–Cu–Zr alloy

The effect of Cr and Yb additions on microstructure and properties of low copper Al–Zn–Mg–Cu–Zr alloy has been investigated. Additions of Cr and Yb to low copper Al–Zn–Mg–Cu–Zr alloy could form 10–20 nm spherical coherent dispersoids, which identified as Zn, Mg, Cu, Cr, Yb-containing Al3Zr with cubic L12 structure. The dispersoids remarkably inhibit recrystallization of Al matrix. The unrecrystallized Al–Zn–Mg–Cu–Zr–Cr–Yb alloy greatly enhanced mechanical properties and fracture toughness as well as the resistance for stress corrosion cracking, compared to Al–Zn–Mg–Cu–Zr alloy.

► Additions of Cr and Yb to low copper Al–Zn–Mg–Cu–Zr alloy could form coherent dispersoids.
► The dispersoids are identified as Zn, Mg, Cu, Cr, Yb-containing Al3Zr.
► The dispersoids remarkably inhibit recrystallization of Al matrix.
► The Al–Zn–Mg–Cu–Zr–Cr–Yb alloy greatly improves alloy properties.