System and method of making single-crystal structures through free-form fabrication techniques

A method of growing a bulk, single-crystal structure using free-form fabrication, comprising:

• (a) providing a substrate having a desired grain that is designated by a grain selector;
• (b) placing feedstock on the substrate and heating the substrate and, thereby, the feedstock, to a desired temperature;
• (c) applying a scanning beam to an upper surface of the feedstock to further heat an entire upper surface of the feedstock to a temperature that exceeds the desired temperature;
• (d) applying the scanning beam to an upper portion of the feedstock simultaneously with step (c) to melt a portion of the upper surface of the feedstock to form a build;
• (e) moving the scanning beam across the entire upper surface of the feedstock to maintain the entire upper surface at a constant temperature such that a two-dimensional thermal gradient is formed in a build direction;
• (f) nucleating and maintaining a solid single crystal in the build based on the desired grain of step (a) as the melted portion of the build solidifies, with higher temperatures of the build near a melting temperature of the feedstock promoting crystal growth in one orientation during a deposition process, rather than promoting additional nucleation, as a grain of the single crystal grows toward the heat of the scanning beam;
• and
• (g) fabricating a solid three-dimensional structure from the build on top of and upward from the substrate.