Abstract
Various techniques have been proposed and developed for aligning the whisker reinforcing phase of metal matrix composites. Most of these techniques involve multi-step alignment processes, and are not suitable for economical, continuous production of metal-whisker com posites.
A laboratory scale, prototype system for the continuous dielectro phoretic deposition and alignment of micron sized, ultra high strength whiskers has been designed, developed and tested. This process consists of the deposition of whiskers onto one of two electrodes placed in a suspension of the whiskers, when a voltage is applied between the electrodes. By employing a metal matrix foil as the deposition elec trode, this technique has demonstrated that the continuous production of metal-whisker combinations suitable for fabrication into advanced whisker reinforced composites is feasible.
The volumetric loading of the reinforcing whiskers on the metal foil can be controlled by varying such process parameters as voltage, foil speed, electrode separation and geometry, and the concentration of whiskers in the supporting media. A discussion of these alignment and deposition process variables is presented.
The metal foils containing the deposited, aligned whiskers are then sandwiched into a preform structure consisting of successive layers of metal foil and fibers. Consolidation of the stacked layers into a com posite is accomplished by hot pressing and diffusion bonding. Photo micrographs of the consolidated composite, showing alignment of the whiskers and the microscopic composite structure are shown and discussed for a range of whisker compositions. Preliminary mechanical properties data for selected composite compositions are presented and discussed.
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