Back to results
US 4,304,613 AGranted
TiNi Base alloy shape memory enhancement through thermal and mechanical processing
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsFrederick E. Wang, William J. Buehler
Life of this patent
Estimating the term…
Abstract
A process for improving the shape change memory properties of a titanium-kel base alloy by (1) heat treating the alloy to convert the TiNi phase to CsCl (B2)-type crystal structure, (2) cold working the alloy to increase the micro-twining, and finally (3) thermal cycling the alloy through the transition temperature range (TTR) while a load is applied in order to improve the orientation of the micro-twins.
Claims24
A process for improving the shape change memory properties of a titanium-nickel base alloy comprising the following steps in order:
- (1) forming a favorable atomic-order in the alloy by
- (a) heating the alloy at a temperature in the range of from just above 700.degree. C. to 800.degree. C. until the TiNi phase has stabilized into disordered body centered cubic (A2) crystal structure;
- (b) slowly cooling the alloy to a temperature in the range of from 600.degree. C. to 700.degree. C.;
- and
- (c) annealing the alloy in the temperature range of from 600.degree. C. to 700.degree. C. until the TiNi phase has been substantially converted from disordered body centered cubic (A2) crystal structure to CsCl(B2)-type crystal structure;
- and then
- (d) slowly cooling the alloy to a temperature in the range of from 450.degree. C. to 550.degree. C.;
- (2) refining the micro-twinning of the alloy crystal structure by
- (a) cold working the alloy in the temperature range of from room temperature to less than 600.degree. C.;
- and then
- (b) annealing the alloy in the temperature range of from 500.degree. C. to less than 600.degree. C.;
- and
- (3) orienting the micro-twins by
- (a) cooling the alloy to a temperature below the shape transition temperature range;
- (b) placing a sufficient load on the alloy to cause from a 5 to less than 8 percent strain in the alloy;
- (c) heating the alloy while still under load to a temperature above the shape transition temperature range;
- (d) cooling the alloy while still under load to a temperature below the shape transition temperature range;
- (e) increasing the load back up to the load applied in substep (3)(b);
- (f) heating the alloy while still under load to a temperature above the shape transition temperature range;
- and
- (g) repeating substeps (3)(d), 3(e), and (3)(f) until the desired degree of micro-twin orientation has been achieved.
18 more elements
Dependencies are inferred from the claim text.