24-10-2012, 10:38 AM
Evaporative Deposition of Aluminum Coatings and Shapes with Grain Size Control
ABSTRACT
The direct deposition of coatings with variable cross-section profiles presents a challenge for the use of physical vapor
deposition technology. Coatings with constant and variable cross-section profiles are of interest for advancing the evaluation
of material behavior under extreme loading conditions, as for example under high strain rate. The synthesis of a variable
cross-section profile by design in the as-deposited condition requires process innovation. It is demonstrated that a thickness
gradient in cross-section can be produced when the substrate is exposed to a highly collimated evaporation source. The
exposure is governed using a variable position shutter as driven by a computer-controlled stepper motor. An example is shown
for aluminum deposition in which the coating thickness varies linearly from one plateau to another forming a wedge shape.
To deposit a controlled grain size in coatings as these wedge shapes, first requires an understanding of the affect of time at
temperature. An examination of aluminum coatings with constant cross-section reveals that ideal-grain growth behavior is
observed from the micron-to-millimeter scale for depositions at temperatures in excess of half the melt point.