NASA Tech Briefs Archive

Extruding Tb/Dy for Magnetostrictive Actuators

Extrusion would yield the required crystal orientation and would be suited to mass production.

NASA's Jet Propulsion Laboratory, Pasadena, California

A process that is undergoing development would be used to mass-produce textured polycrystalline rods of a terbium/dysprosium alloy for cryogenic magnetostrictive actuators. The rolling-and-heat-treatment process described in the preceding article yields a high degree of crystal orientation, but is suitable for small batches only. The developmental process is expected to be inexpensive to provide greater uniformity in larger batches in a mass-production setting.

The process exploits an established coextrusion technique in which a tube is filled with a material, then the tube and its contents are redrawn to a smaller diameter. The uniform stretch of the tube and its contents yields a high degree of orientation of crystals along the axis of the tube.

First, the unoriented polycrystalline Tb/Dy is encased in a tube of 316L stainless steel. Then the filled tube is drawn through a die sized to increase the length of the tube by a factor of 4. Finally, the tube is split to remove the polycrystalline Tb/Dy rod. The degree of parallel alignment and long-axis orientation of the crystals in the drawn rod is sufficient for an effective magnetostrictive actuator.

This work was done by Robert Chave, Jennifer Dooley, Brent Fultz, and Marius Birsan of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at under the Materials category.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

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