Microstructure characteristics of an ultra-high strength extruded Al-4.7Cu-1Li-0.5Mg-0.1Zr-1Zn alloy during heat treatment

In this work, a novel Al-4.7Cu-1Li-0.5Mg-0.1Zr-1Zn alloy was designed with the purpose of developing ultra-high strength and low-cost Al-Cu-Li alloy. The mechanical properties and microstructure evolution of the studied alloy under T6, T8, and two-stage aged conditions were investigated. The alloy showed a non-recrystallization feature during solution treatment. A strong < 111 > fiber texture was presented in the as-quenched alloy. The yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of the alloy was largely depended on the aging process parameters. A good combination of ultra-high strength (YS = 731 MPa, UTS = 753 MPa) and ductility (EL = 5.5%) were obtained in the T8 treated specimen (pre-stretched by 3% and aged at 150 degrees C for 32 h). The pre-strain prior to artificial aging and aging temperature significantly affect the distribution, density, and size of precipitates. Strengthening mechanism of the alloy was discussed in detail. The strong < 111 > texture preserved in the as-quenched alloy and the finely dispersed T-1 (Al2CuLi) phases distributed in the T8 treated specimens could account for the ultra-high strength of the present alloy. (C) 2019 Elsevier B.V. All rights reserved.