Microstructure and Mechanical Properties of Ultra-high Strength Al-7.88Zn-2.05Mg-1.70Cu-0.19Er Aluminum Alloy Thin Strip

The microstructure, mechanical properties, and corrosion resistance of ultra-high strength cold-rolled thin strips of Al-7.88Zn-2.05Mg-1.70Cu-0.19Er alloy were investigated. Results reveal that the excellent comprehensive properties of the cold-rolled thin strips with 0.5 mm in thickness are achieved after solid solution treatment of 475 degrees C/1 h/water quenching and double aging treatment of 120 degrees C/6 h+150 degrees C/24 h. The hardness, ultimate tensile strength, yield strength, and elongation of the thin strips are 1859.1 MPa, 669.4 MPa, 624.1 MPa, and 11.2%, respectively. The mechanical properties of double-aged strip are comparable to those of alloy after peak-aging treatment. The electrical conductivity, exfoliation corrosion rating, and stress corrosion cracking sensitivity of the thin strip are 35.5%IACS, EA, and 4.07%, respectively. The fine spherical Al-3(Er, Zr) and eta' phases are uniformly distributed in the Al matrix, and most precipitates are coherent with Al matrix lattice. The tiny discontinuous grain boundary precipitate eta phase mainly causes the lower stress corrosion sensitivity of the studied alloy.