“…For AI-Zn binary alloys, it has been shown that the miscibility gap for GP zones (Gerold, 1961;Sato & Kojima, 1979;Satyanatayana, 1981) explains the reversion phenomena very well (Wendrock & LOftier, 1981;Okuda, Osamura, Hashizume & Amemiya, 1988;Truong, Wendrock & LOftier, 1991), although there are still arguments on the rate-determining process (Gerstenberg & Gerold, 1985). In previous investigations (Okuda, Osamura, Hashizume & Amemiya, 1988;Okuda, Osamura, Amemiya & Hashizume, 1989), we have examined the reversion processes of rather large (2.5-4.5 nm Guinier radius) GP zones in AI-Zn alloys and found that the reversion process is well understood as a dissolution process under a local metastable equilibrium.…”