抄録
The growth, reversion and critical nucleus size of G.P. [I] zones in Al–Cu alloys have been investigated by using the stress orienting effect combined with two step aging. Growth and reversion of the zones have been detected by the length change measurement. The critical temperatures of the complete reversion of G.P. [I] zones have been determined through the morphological change induced by free aging after stress aging; below the critical temperature, the structure demonstrated by G.P. [II] or θ′ follows the stress orienting effect on G.P. [I]. The critical nucleus size of G.P. [I] zones has been estimated to be ∼1.0 nm, corresponding to 6∼8 copper atoms in it.
