Microstructure and Properties of an Al-Zn-Mg-Cu Alloy Plate

Abstract

The inhomogeneous microstructure and properties at typical position of an Al-7.7Zn -1.7Mg-1.4Cu-0.11Zr alloy plate in T7651 condition have been investigated using OM, TEM and EBSD analysis, tensile properties testing, conductivity measurement and fracture toughness testing. The results indicate that there are obvious differences in grain morphology, quench-introduced precipitation and recrystallization degree in the two typical positions of near the surface layer (T/8 plane) and in the center (T/2 plane) along the thickness direction of the plate. There appear some amount of quench-introduced precipitates at the T/2 plane of the alloy plate, which improves the electrical conductivity. And there is a higher proportion of the recrystallization organization at the T/2 plane of the alloy plate, seriously affecting its elongation and fracture toughness. Due to without marked characteristic of rolling flow line, the strength at the T/8 plane of the alloy plate is lower. The properties at T/8 plane and at T/2 plane of the alloy plate exhibit a difference of 3~18%. Microstructure inhomogeneity of the alloy plate determines the uniformity of its properties.