Effect of small content Cu on microstructure and properties of spray deposited Al-Li alloy

Al-Li alloy containing high content of Li and its modified alloy with 0.5% Cu are prepared by spray deposited processing, and then extruded and aged. Microstructure and tensile properties at room temperature are determined for the two alloys at different conditions. The results show that spray deposited Al-3.8Li-l.0Mg-0.4Ge-0.2Zr alloy possess a fine equiaxed microstructure and precipitates Al₄Li₉ and δ-AlLi phases. Large amounts of δ′-AlLi phases are formed after aging. The addition of 0.5% Cu to the alloy leads to an improvement of 30-48 MPa and 44 MPa for yield strength and ultimate tensile strength respectively. The reason of improvement is due to the solid-solution strengthening effect of Cu and the decrease of the solid solubility of Li in the matrix leading to the higher volume fraction of δ′ phases.