Abstract: The formation and the coarse of δ′ phase in 1420 Al- Li alloy treated by retrogression and reaging were investigated by means of smal l angle X-ray scattering (SAXS) technique. It was found that there existed atr ansition zone between δ′ phase and matrix for 5 h reaging treatment, and the transition zone disappeared for 48 h reaging, then the coarsening of δ′ particl es was caused by their swallowing up each other.

Key words: Al-Li alloy, δ′ phase, transition zone