Exploration of Phase Dissolution during Solution Treatment for a New Al-3.86Cu-0.89Li-0.38Mg-0.28Ag Alloy

Abstract

The dissolution of the second phase during solution treatment was of great importance for achieving preferential properties via aging treatment for Aluminum-Lithium (Al-Li) alloys. The microstructure characteristics of an extruded Al-Li alloy and its second phase dissolution during solution treatment were studied, while related electrical conductivity and tensile properties after ageing were tested for verification. The results indicated that as the alloy solution was treated from 500°C to 520°C with a soaking time of 1.5h, the Cu-rich phase dissolved into the matrix continuously. The statistics of remained phase area fraction ascertained no obvious decrement from 510°C to 520°C and only Fe-containing phase with large size was detected. Meanwhile, tensile properties under the same aging regime declared a higher strength was obtained at 510°C. As the solution time varied from 0.5h to 5h at 510°C, the Cu-rich phase was detected in a soaking time of 0.5h while disappeared after 1.5h and only the Fe-containing phase was observed. Correspondingly, electrical conductivity exhibited a moderate growth while tensile strength obviously increased from 0.5h to 1.5h and then maintained a platform, which revealed a preferential solution regime of 510°C/1.5h. This gives a reference for the second phase dissolution during solution treatments and furtherly obtaining preferential solution regimes.