Phase stability in Al/Ti multilayers

Structural stabilities in thin-film Al/Ti multilayers have been studied usi ng transmission electron microscopy. It is shown that models based on inter face-induced modifications to bulk stacking fault energies, and/or coherenc y-strain energy may not be used to explain the various phase transitions ob served. Rather, phase stability may be rationalized by reference to a new m odel based on classical thermodynamics, involving the competition between b ulk and interfacial energies. Thus, these phase transitions are shown to be driven by reductions in the overall interfacial energies. A biphase diagra m (reciprocal of bilayer thickness vs composition) has been developed for t he multilayers produced by magnetron sputtering. The influence of impuritie s possibly introduced during thin-foil preparation is considered and ration alized by reference to the biphase diagram for this system. (C) 1999 Publis hed by Elsevier Science Ltd. On behalf of Acta Metallurgica. All rights res erved.