FORMATION OF SECOND PHASE PARTICLES IN ALUMINUM-COPPER ALLOY FILMS

The formation of second phase particles in Al plus 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 degree C or 6 h at 130 degree C are necessary to produced G. P. zones THETA prime particles are nucleated after approximately 100 h at 120 degree C without formation of THETA double prime . The stable THETA -Al//2Cu precipitate was found at temperatures as low as 150 degree 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 THETA -CuAl//2.