Lightweight metals: high-strength 7-series aluminium alloys

Lightweight metals: high-strength 7-series aluminium alloys

Today we are going to give a brief introduction to the basics of high-strength 7-series aluminium alloys. This will involve some knowledge of optimised alloys, microstructures and heat treatment processes.

High-strength 7-series aluminium alloys (Al-Zn-Mg-Cu system) are a major structural material in aerospace because of their low density and high strength. With the recent demand for lighter vehicles, more and more car companies are using it to reduce weight, with electric vehicles being particularly prominent. For example, the body of the Azera vehicle uses approximately 97% aluminium alloy, including the 7003 high-strength aluminium alloy developed by Novelis, for safety and weight reduction purposes. 7-series high-strength aluminium alloys are becoming one of the hot spots in the development of lightweight structural materials around the world. By optimising the alloy composition, using advanced billet making methods, forming, processing and heat treatment processes, researchers are developing higher strength aluminium alloys with improved performance. It has high strength (yield strength above 600 MPa), high toughness and corrosion resistance, and lower cost.

In the mid-20th century, 7075 and B95 high-strength aluminium alloys were developed in the USA and the former Soviet Union respectively by adding Mn, Cr and Ti to Al-Zn-Mg-Cu alloys to improve the stress corrosion resistance of SCC, and in 1972 Alcoa developed 7050 aluminium alloy by reducing the content of Fe and Si impurities and replacing Cr with Zr. After the 1970s, developed countries concentrated on Research in two areas.

1, the development of heat treatments, such as the Alcoa 7150-T77 alloy in the late 1980s.

2, the development of rapid solidification/powder metallurgy RS/PM processes, such as the development of high tensile strength 700 MPa aluminium alloys in Japan in '92.