The alloy microstructure was changed in the process of aging.After 700 ℃×2 h solution treatment

the microstructure of rolling specimens consists of α0 single phase with face-centered cubic crystal.The matrix α0 phase exhibits different phase decomposition depending on ageing time and constituents.At 2 hour aging

the matrix α0 phase exhibits a spinodal decomposition and transform into the α’0 modulation structure.The spinodal decomposition appears with the help of Cu atoms migration due to the generation of many vacancies from the quenching.Early stage of ageing at 400 ℃

the matrix α0 phase transform α’0 modulation structure.With increasing in the ageing time

the α’0 transform into AuCuI ordered phase

age-hardening appears.Finally

all the α’0 is changed into AuCuI ordered phase.