Abstract: In the preparation process of 7X50 aluminum alloy wire, intermediate annealing-cold drawing-cold heading and other intermediate processes are required. After single-stage annealing, the wire often occurs natural aging and strength increases, which seriously affects the re-drawing forming. The microstructure and properties of the single-stage and double-stage intermediate annealed 7X50 aluminum alloy wires were analyzed by means of optical microscope, transmission electron microscope and electronic tensile testing machine. The results show that partial recrystallization occurs after single-stage annealing at 404 ℃ for 2 h, and the strength decreases from 235 MPa(before annealing) to 188 MPa, and increases to 244 MPa after placing for 270 d because of obvious natural aging effect. After double-stage annealing at 404 ℃ for 2 h and 233 ℃ for 4 h, partial recrystallization occurs and the strength decreases to 173 MPa, and no obvious natural aging hardening effect occurs during the 270 d placing. The second stage 233 ℃×4 h annealing holding process promotes the precipitation and growth of AlZnMgCu phases and Mg, Zn phases, which consumes a large amount of Zn, Mg elements, effectively eliminates the natural aging hardening effect during the process of placing.

Key words: 7X50 aluminum alloy wire, annealing, recrystallization, natural aging