# US 2019/0161832 A1 · Shape Memory Alloy Wire With Controlled Energy Damping

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- Number: US 2019/0161832 A1
- Document ID: US20190161832A1
- Status: Published application
- Kind: A1
- Application number: 16/259,137
- Filed: 2019-01-28
- Published: 2019-05-30
- Earliest claimed: 2016-05-13
- Assignees: Massachusetts Institute of Technology
- Applicants: Massachusetts Institute of Technology
- Inventors: Christopher Schuh; Stian Melhus Ueland
- Web page: https://patentgrep.com/patent/US20190161832A1

## CPC

- C22C 9/04: with zinc as the next major constituent
- C22C 9/01: with aluminium as the next major constituent
- C22F 1/08: of copper or alloys based thereon
- C25F 3/22: of heavy metals
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- 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)
- C25F: PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR

## Abstract

There is provided a shape memory alloy wire with a length of polycrystalline shape memory alloy having an alloy composition including at least one member selected from the group consisting of Cu in at least 10 wt. %, Fe in at least 5 wt. %, Au in at least 5 wt. %, Ag in at least 5 wt. %, Al in at least 5 wt. %, In in at least 5 wt. %, Mn in at least 5 wt. %, Zn in at least 5 wt. % and Co in at least 5 wt. %, and having a martensite crystal structure consisting of one of 2H, 18R1, M18R, and 6R. The length of polycrystalline shape memory alloy has a cross sectional wire diameter greater than 1 micron and less than 500 microns, an oligocrystalline morphology including polycrystalline grains that span the wire diameter and a wire surface with a surface roughness that is no greater than about 100 nanometers.

## Claims

### Claim 1

A shape memory alloy wire comprising:
a length of a polycrystalline shape memory alloy having an alloy composition including at least one member selected from the group consisting of Cu in at least about 10 wt. %, Fe in at least about 5 wt. %, Au in at least about 5 wt. %, Ag in at least about 5 wt. %, Al in at least about 5 wt. %, In in at least about wt. %, Mn in at least about 5 wt. %, Zn in at least about 5 wt. % and Co in at least about 5 wt. %, the shape memory alloy composition having a martensite crystal structure consisting of one of 2H, 18R1, M18R, and 6R;
the length of a polycrystalline shape memory alloy having a cross sectional wire diameter greater than about 1 micron and less than about 500 microns;
the length of a polycrystalline shape memory alloy having an oligocrystalline morphology including polycrystalline shape memory alloy grains that span the cross sectional wire diameter; and
the length of a polycrystalline shape memory alloy having a wire surface with a surface roughness no greater than about 100 nanometers.

### Claim 2 (depends on 1)

The shape memory alloy wire of claim 1 wherein the cross sectional wire diameter has an extent that causes energy dissipation by the shape memory alloy wire during a martensitic phase transformation to be dominated by surface roughness of the oligocrystalline shape memory alloy wire.

### Claim 3 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy wire cross sectional diameter is less than about 250 microns.

### Claim 4 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy wire cross sectional diameter is less than about 100 microns.

### Claim 5 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy wire cross sectional diameter is greater than about 10 microns.

### Claim 6 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy wire cross sectional diameter is greater than about 100 microns.

### Claim 7 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy composition comprises Cu—Zn—Al.

### Claim 8 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy composition comprises Cu-14Al-4Ni (wt. %).

### Claim 9 (depends on 1)

The shape memory alloy wire of claim 1 wherein the shape memory alloy cross sectional wire diameter is greater than about 20 microns and less than about 250 microns.

### Claim 10 (depends on 1)

The shape memory alloy wire of claim 1 wherein the length of polycrystalline shape memory alloy has a surface roughness characterized by an arithmetic average surface roughness, Ra, no greater than about 80 nanometers.