Microstructure, mechanical properties and corrrosion behavior of Al-Zn-Mg-Cu wire under different annealing conditions

Abstract

Al-Zn-Mg-Cu aluminum alloy wires were annealed at 404 °C and then cooled at 10–100 °C/h. On the basis of the cooling speed of 10 °C/h, a second stage of 232 °C annealing was added and held for 4–8 h. The differences in grain organization, grain boundary precipitation phase, electrical conductivity, mechanical properties and intergranular corrosion properties of Al-Zn-Mg-Cu aluminum alloy wires with different annealing processes were comparatively investigated by using electron backscatter diffraction (EBSD) technique, transmission electron microscope (TEM), electronic tensile tester, conductivity meter. It is found that the grain size of Al-Zn-Mg-Cu wire after different annealing processes has not grown significantly, and the grain orientation has not changed obviously. As the cooling speed decreased from 100 °C/h to 10 °C/h, the precipitated η phase continued to merge and grow, from chain distribution to independent distribution, and the Cu element in η phase increase. The Cu content of η phase increases to 14.7 wt% by adding a second annealing stage. The conductivity of the alloy increases to 48.6 %IACS and the tensile strength is reduced to 168 MPa. In addition, the maximum corrosion depth of the alloy is reduced to 16 μm. It shows good mechanical properties and excellent corrosion resistance.

Keywords

• Al-Zn-Mg-Cu aluminum alloy
• Wire material
• Annealing
• Grain structure
• Intergranular corrosion
• Mechanical properties