# US 9,752,219 B2 · Self-adaptive, ultra-low elastic modulus shape memory alloys

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- Number: US 9,752,219 B2
- Document ID: US9752219B2
- Status: Granted
- Kind: B2
- Application number: 14/442,494
- Filed: 2013-11-15
- Published: 2016-09-29
- Granted: 2017-09-05
- Earliest claimed: 2012-11-16
- Assignees: The Texas A&M University System
- Applicants: The Texas A&M University System
- Inventors: Ji Ma; Ibrahim Karaman
- Web page: https://patentgrep.com/patent/US9752219B2

## CPC

- C22F 1/006: {Resulting in heat recoverable alloys with a memory effect}
- A61L 27/06: Titanium or titanium alloys
- A61L 31/022: {Metals or alloys}
- C22C 1/02: by melting {(C22C1/1036 takes precedence)}
- C22C 14/00: Alloys based on titanium
- C22F 1/183: {of titanium or alloys based thereon}
- A61L 2400/16: Materials with shape-memory or superelastic properties
- A61L 2430/02: for reconstruction of bones; weight-bearing implants
- A61L 2430/12: for dental implants or prostheses
- A61L 2430/24: for joint reconstruction
- A61L 2430/38: for reconstruction of the spine, vertebrae or intervertebral discs
- C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00)
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

Methods of manufacturing biocompatible, corrosion resistant, self-adaptive, shape-memory titanium-based alloys by using specific ranges of elements in the alloy. Subsequent to melting, the alloy may undergo heat treating, thermo-mechanically processing, and training. Subsequent to training, the alloy has an ultra-low elastic modulus and exhibits self-adaptive, superelastic behavior.

## Claims

### Claim 1

A method of making a shape-memory alloy comprising:
(a) melting titanium (Ti) and niobium (Nb) to form an alloy:
(b) heat treating the alloy formed in (a);
(c) thermo-mechanically processing the alloy: and
(d) training the alloy via a plurality of deformation cycles to reduce an effective modulus of elasticit of the alloy below 30.0 GPa wherein (d) occurs after (c), and wherein (d) comprises cyclically subjecting the alloy to a 1-3% strain at a temperature between about 20° C. (68° F.) and about 50° C. (122° F.).

### Claim 2 (depends on 1)

The method of claim 1, wherein the atomic % of Nb in the alloy is between about 23 at. % and about 26 at. %.

### Claim 3 (depends on 1)

The method of claim 1, wherein (c) comprises at least one of hot-working, warm extrusion, cold extrusion, rolling, swaging, equal channel angular pressing, and wire drawing, or combinations thereof.

### Claim 4 (depends on 3)

The method of claim 3, wherein the (c) comprises subjecting the alloy to a strain greater than 10% of the Von mises equivalent strain.

### Claim 5 (depends on 3)

The method of claim 3, further comprising heat treating the alloy after (c) using a plurality of heat treat cycles, wherein each heat treat cycle of the plurality of heat treat cycles comprises: maintaining the alloy at a temperature between about 300° C. and about 600° C. for 5 minutes to 60 minutes followed by a water quench.

### Claim 6 (depends on 1)

The method of claim 1, wherein (b) comprises maintaining the alloy at a temperature between 850° C.-1100° C. before (c).

### Claim 7 (depends on 6)

The method of claim 6, wherein (b) comprises heat treating the alloy for at least 30 minutes.

### Claim 8 (depends on 1)

The method of claim 1, wherein (b) further comprises water quenching the alloy after heat treating the alloy.

### Claim 9 (depends on 1)

The method of claim 1, wherein (d) comprises cyclically subjecting the alloy to strains larger than 0.5% strain in the austenite phase at a temperature below 150° C.

### Claim 10

A method of manufacturing a corrosion resistant, shape-memory alloy comprising:
(a) melting titanium (Ti) and nickel (Ni) to form the alloy;
(b) heat treating the alloy using a first heat treat process;
(c) thermo-mechanically processing the alloy; and
(d) training the alloy via a plurality of deformation cycles to obtain an effective modulus of elasticity less than 40 GPa.

### Claim 11 (depends on 10)

The method of claim 10, wherein the atomic % of Ni is between about 49.5 at. % and about 55 at. %.

### Claim 12 (depends on 10)

The method of claim 10, wherein (c) comprises at least one of hot deformation, warm deformation, or cold deformation.

### Claim 13 (depends on 12)

The method of claim 12, wherein the at least one of hot, warm, or cold deformation comprises rolling, swaging, equal channel angular pressing, and wire drawing, or combinations thereof.

### Claim 14 (depends on 12)

The method of claim 12, wherein the cold deformation comprises applying a strain to the alloy greater than 10% of Von mises equivalent strain.

### Claim 15 (depends on 10)

The method of claim 10, wherein (b) comprises maintaining the alloy at a temperature between about 800° C. and about 1000° C. before (c).

### Claim 16 (depends on 10)

The method of claim 10, wherein (b) is performed for at least 30 minutes.

### Claim 17 (depends on 10)

The method of claim 10, wherein (b) is performed for 1 to 24 hrs.

### Claim 18 (depends on 10)

The method of claim 10, wherein (b) is performed for 24 to 72 hrs.

### Claim 19 (depends on 10)

The method of claim 10, further comprising water quenching the alloy after (c).

### Claim 20 (depends on 10)

The method of claim 10, wherein the hot deformation process comprises applying a strain to the alloy greater than 50% of Von mises equivalent strain.

### Claim 21 (depends on 10)

The method of claim 10, further comprising heat treating the alloy using a second heat treatment process after (c), wherein the second heat treatment process comprises maintaining the alloy at a temperature of 200° C. to 500 ° C. for 30 minutes to 100 hours.

### Claim 22 (depends on 10)

The method of claim 10, wherein (d) comprises cyclically loading the alloy to 1-5% strain at a temperature between about 20° C. and about 50° C.

### Claim 23 (depends on 22)

The method of claim 22, wherein the loading and unloading of the cyclical loading is performed 100-10000 times.

### Claim 24 (depends on 10)

The method of claim 10, wherein (d) comprises cyclically loading the alloy to strains larger than 0.5% strain in the austenite phase at a temperature below 150° C.

### Claim 25

A method of manufacturing a corrosion resistant, shape-memory alloy comprising:
(a) melting titanium (Ti) and nickel (Ni) to form the alloy;
(b) heat treating the alloy using a first heat treat process;
(c) thermo-mechanically processing the alloy; and
(d) training the alloy, to obtain an effective modulus of elasticity less than 40 GPa, wherein training the alloy comprises cyclically loading the alloy to 1-5% strain at a temperature between about 20° C. and about 50° C.

### Claim 26 (depends on 25)

The method of claim 25, wherein the loading and unloading of the cyclical loading is performed 100-10000 times.

### Claim 27 (depends on 25)

The method of claim 25, wherein (d) comprises cyclically loading the alloy to strains larger than 0.5% strain in the austenite phase at a temperature below 150° C.

### Claim 28

A method of making a shape-memory alloy comprising:
(a) melting titanium (Ti) and niobium (Nb) to form an alloy;
(b) heat treating the alloy formed in (a);
(c) thermo-mechanically processing the alloy; and
(d) training the alloy, wherein, subsequent to training, the alloy has an effective modulus of elasticity less than 30.0 GPa, wherein training the alloy occurs after (c), and wherein training the alloy comprises cyclically subjecting the alloy to a 1-3% strain at a temperature between about 20° C. (68° F.) and about 50° C. (122° F.).