Formation of second phase particles in aluminum-copper alloy films

The formation of second phase particles in Al+3% Cu alloy films was examined in order to find differences of the precipitation in thin films from that occurring in bulk alloys. Compared to bulk alloys in the thin film material the formation of Guinier-Preston zones is retarded. In well quenched thin films 60 h at 100°C or 6 h at 130°C are necessary to produce G.P. zones. θ′ particles are nucleated after approximately 100 h at 120°C without formation of θ″. The stable θ-Al2Cu precipitate was found at temperatures as low as 150°C on the film surface. The results show that excess vacancies cannot be retained in thin films and that the film surfaces provide preferential nucleation sites for the equilibrium precipitate θ-CuAl2. © 1972.