Accession Number : ADA019045

Title :   The Influence of Surface Films on Mechanical Properties.

Descriptive Note : Technical rept.,

Corporate Author : VIRGINIA UNIV CHARLOTTESVILLE RESEARCH LABS FOR THE ENGINEERING SCIENCES

Personal Author(s) : Wilsdorf,H. G. F.

Report Date : DEC 1975

Pagination or Media Count : 28

Abstract : The variables that influence the mechanical behavior of metals covered with thin films have been enumerated. In particular, factors affecting dislocation glide in the surface region have been characterized in terms of image stresses taking into account both the free surface and the accommodation dislocation network at the substrate-film interface. A reduction of yield stress of 50% or more was measured on copper crystals electro-plated with 600 A films of nickel, gold or alpha-brass, all of which are epitaxial overgrowths. The complexity of the microstructure in the substrate-thin film composite has been described and the consequences on dislocation glide explored. An example of a system which exhibits an increase of the critical resolved yield stress, tau sub y, is given. Here, diffusion layers less than 1 micrometer thick caused tau sub y to increase by a factor of two, a consequence of the hindering of glide dislocations by accommodation dislocation networks.

Descriptors :   *Copper, *Coatings, *Yield strength, *Metal films, Mechanical properties, Thin films, Electrodeposition, Nickel, Gold, Brass, Defects(Materials), Interfaces, Diffusion, Epitaxial growth

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE