• Bajtošová, Lucia
• Šíma, Vladimír
• Mára, Vladimír
• Procházka, Ivan
• Očenášek, Vladivoj
• Leibner, Michal
• Zikmund, Sebastien
• Kodetová, Veronika
• Kudrnová, Hana
• Cieslar, Miroslav
• Vlach, Martin
• Čížek, Jakub

Abstract

<jats:p>The commercial Al–Zn–Mg–Cu-based alloys (7xxx series) are widely used in metalworking, automotive and aircraft industries as well as in aeronautical applications. The positive effect of the Sc,Zr-addition on mechanical properties of laboratory Al-based alloys is generally known. The microstructure, mechanical and thermal properties of the conventionally cast, heat-treated and cold-rolled Al–Zn–Mg–Cu (–Sc–Zr) alloys during isochronal annealing and natural ageing were studied. Microstructure observation by scanning electron microscopy and transmission electron microscopy proved the Zn,Mg,Cu-containing eutectic phase at grain boundaries. The distinct changes in microhardness curves as well as in a heat flow of the alloys studied are mainly caused by dissolution of the clusters/Guinier-Preston (GP) zones and precipitation of particles from the Al–Zn–Mg–Cu system. An easier diffusion of Zn, Mg and Cu atoms along dislocations in the cold-rolled alloys is responsible for the precipitation of the Zn,Mg,Cu-containing particles at lower temperatures compared to the cast alloys. Microhardness values of the heat-treated alloys increase immediately from the beginning of natural ageing due to the formation of the clusters/GP zones. Addition of Sc and Zr elements results in a higher hardness above ~ 270 °C due to a strengthening by coherent secondary Al<jats:sub>3</jats:sub>(Sc,Zr) particles with a good thermal stability. Sc,Zr-addition has probably no influence on the evolution of the solute clusters/GP zones.</jats:p>

Topics

• impedance spectroscopy
• cluster
• grain
• Cu-containing
• phase
• scanning electron microscopy
• aluminium
• hardness
• transmission electron microscopy
• dislocation
• precipitation
• aging
• annealing