CONTROLLING STRENGTH AND TOUGHNESS OF MULTILAYER FILMS - A NEW MULTISCALAR APPROACH

Multiscalar films are produced in order to combine both toughness and strength into a multilayer film. These structures incorporate both a s trengthening phase and a toughening phase in a compositionally modulal ed microcomposite. The mechanical properties and microstructure for th ick (approximately 50 mum) Mo/W multiscalar films have been characteri zed. A detailed microstructural analysis (including transmission elect ron microscopy, scanning electron microscopy, and x-ray techniques) of Mo/W multiscalar films has shown that large single-crystal columns of Mo interspersed with epitaxial layers of W extend for the entire film thickness. The microstructure is a zone-II-type microstructure, yet t he temperatures during deposition are well below the lower limit (0.3 T/T(m)) previously reported for such microstructures. Hardness and ten sile tests have shown that a multiscalar approach is capable of tailor ing a desired strength and toughness into a multilayered film.