Effects of temperature and strain rate during hot rolling on microstructure and tensile properties of high-strength Al–Zn–Mg–Cu alloy

Abstract

The effects of temperature and strain rate during hot rolling on the microstructure and tensile properties of high-strength Al–Zn–Mg–Cu alloy were investigated. Hot rolling was performed with controlled temperature (300°C, 350°C, 400°C) and strain rate (0.3/s, 2.0/s). Hot-rolled samples were prepared by solution heat treatment followed by T6 aging treatment. With the increase of the Z parameter calculated from the temperature and strain rate during hot rolling, the 0.2% proof stress after T6 treatment increased by up to 20 MPa at the surface region of the rolled sheets and by up to 8 MPa at the center region. This is because the average subgrain diameter became smaller as the Z parameter increased. In addition, the 0.2% proof stress of the center region of the rolled sheets was about 70 MPa higher than that of the surface region. At the center region, the orientation densities of Brass texture ({011}〈211〉), S texture ({123}〈634〉), and Cu texture ({112}〈111〉) were higher than that of the surface region. Therefore, the Taylor factor was higher at the center region than the surface region, and as a result, the 0.2% proof stress of the center region became high.