Precipitation hardening and intergranular corrosion behavior of novel Al-Mg-Zn(-Cu) alloys

High-performance aluminum alloys are desired for applications that require lightweight materials, but it is challenging to overcome the tradeoff between their strength and intergranular corrosion resistance. To overcome this tradeoff, we have prepared novel Al-Mg-Zn (-Cu) alloys with highly Zn content combined with Cu addition. The alloys with a (Zn + Cu)/Mg ratio below 1.5 are different from traditional 2000, 5000 and 7000 series aluminium alloys. The results show that the number density and lattice spacing of intragranular precipitates increase, while the precipitate sizes decreases with the increase of (Zn + Cu)/Mg ratio, which is the reason for the increase of the alloy strength. Meanwhile, the intergranular corrosion resistance of the alloys is also enhanced by decreasing the potential between grain boundary precipitates and the Al matrix, especially in alloys with high (Zn + Cu)/Mg ratios. These results provide a new method for obtaining high-strength and corrosion-resistant aluminum alloys. (c) 2020 Elsevier B.V. All rights reserved.

Automated summary

The research found that by increasing the zinc and copper content in Al-Mg-Zn(-Cu) alloys, the strength and corrosion resistance of the alloy can be improved. The density and lattice spacing of intragranular precipitates increase while precipitate sizes decrease, resulting in increased strength. Additionally, enhancing the intergranular corrosion resistance can be achieved by reducing the potential between grain boundary precipitates and the Al matrix.