AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Paper TF-MoA2
Structure and Properties of Exothermic Metal Multilayers

Monday, November 15, 2004, 2:20 pm, Room 303C

Session: Mechanical Properties of Thin Films
Presenter: D.P. Adams, Sandia National Laboratories
Authors: D.P. Adams, Sandia National Laboratories
C. Tigges, Sandia National Laboratories
M.A. Rodriguez, Sandia National Laboratories
T. Buccheit, Sandia National Laboratories
Correspondent: Click to Email
Multilayer thin films composed of reactive material pairs are currently of interest for brazing, joining and other applications. As shown extensively by Weihs et.al. several thin film material systems can be stimulated such that a rapid, self-propagating reaction occurs within a multilayer. These layers have great potential for joining, because they act as a localized, short-lived heat source. In this talk, we evaluate the properties and microstructure of two multilayer systems, Co/Al and Pt/Al, which have vastly different heats of formation. Each material system was deposited by magnetron sputtering to thicknesses in excess of 1 micron having different designs. Propagation velocities were measured by high-speed photography for both material systems, and speeds are shown to depend on bilayer thickness, premixed volume, heat of formation and substrate thermal properties. Critical thicknesses required for propagation (when attached to substrates) have been identified and are described through comparison with analytical models. Secondly, we discuss the microstructure and mechanical properties of reacted films. New (previously not reported) phases have been found after exhibiting a self-propagating exothermic reaction. For example, rhombohedral AlPt has been produced in reacted Al/Pt multilayers. We currently attribute this to the rapid quench rate following reaction to high combustion temperatures. The mechanical properties (hardness, toughness) of reacted films are also investigated, because these are critical to future applications. Attempts are made to relate these properties to reacted film microstructure.