RAPID SOLIDIFIED DUCTILE Cu-Al-Mn RIBBON FOR ELASTOCALORIC APPLICATIONS

Abstract

A ribbon of elastocaloric material is provided. The ribbon is made from copper alloyed with aluminum and manganese. The ribbon has a length, a width, and a thickness. The length is a longest dimension of the ribbon, and the width is perpendicular to the length. The thickness is perpendicular to both the length and the width, and the thickness is 0.1 mm or less. Further, in a room temperature ambient environment, the ribbon increases in temperature by at least 4 C. upon application of 6% of tensile strain and cools by at least 4 C. when the tensile strain is unloaded.

Claims

1. A ribbon of elastocaloric material, comprising: copper alloyed with aluminum and manganese; wherein the ribbon comprises a length, a width, and a thickness, the length being a longest dimension of the ribbon, the width being perpendicular to the length, and the thickness being perpendicular to both the length and the width, the thickness being 0.1 mm or less; and wherein, in a room temperature ambient environment, the ribbon increases in temperature by at least 4 C. upon application of 6% of tensile strain and cools by at least 4 C. when the tensile strain is unloaded.

2. The ribbon of elastocaloric material of claim 1, wherein a microstructure of the ribbon is oligocrystalline comprising columnar grains extending across a thickness of the ribbon separated by intergrain nodes and wherein the columnar grains each comprise a width, the width being at least twice the thickness.

3. The ribbon of elastocaloric material of claim 2, wherein the ribbon exhibits an induced magnetic moment of at least 1 emu/g in an applied magnetic field of 30 kOe.

4. The ribbon of elastocaloric material of claim 2, wherein the ribbon exhibits a latent heat of martensitic transformation of at least 5.0 J/g.

5. The ribbon of elastocaloric material of claim 2, comprising an elastic modulus of at least 10 GPa.

6. The ribbon of elastocaloric material of claim 2, comprising a yield strength (.sub.0.2) of at least 50 MPa.

7. The ribbon of elastocaloric material of claim 2, comprising a critical transformation stress of at least 50 MPa.

8. The ribbon of elastocaloric material of claim 2, comprising an ultimate tensile strength of at least 200 MPa.

9. The ribbon of elastocaloric material of claim 2, comprising a total strain before failure of at least 5%.

10. The ribbon of elastocaloric material of claim 1, wherein a microstructure of the ribbon comprises columnar grains extending across a thickness of the ribbon and wherein the columnar grains each comprise a width, the width being more than the thickness.

11. The ribbon of elastocaloric material of claim 1, wherein the copper alloyed with aluminum and manganese comprises a formula of Cu.sub.72Al.sub.xMn.sub.y, where x=175, and y=115.

12. The ribbon of elastocaloric material of claim 1, wherein the copper alloyed with aluminum and manganese further comprises up to 5 at % of a metal selected from a group consisting of Ni, Ag, Au, Zn, Sn, Ti, Cr, Fe, Co, Si, and combinations thereof.

13. A cloth comprising at least one ribbon of elastocaloric material according to claim 1.

14. A method of preparing a ribbon elastocaloric material, the method comprising: directing a stream of the elastocaloric material in a molten form onto an outer surface of a rotating wheel, the elastocaloric material comprising copper alloyed with aluminum and manganese; cooling the stream of elastocaloric material on the outer surface of the rotating wheel to form the ribbon; and removing the ribbon from the outer surface of the rotating wheel; wherein the ribbon comprises a thickness as measured perpendicular to the outer surface, the thickness being 0.1 mm or less.

15. The method of claim 14, further comprising annealing the ribbon at a temperature in a range from 600 C. to 1100 C. for a time in a range from 5 minutes to 10 hours.

16. The method of claim 14, further comprising aging the ribbon at a temperature in a range from 50 C. to 500 C. for a time in a range from 1 minutes to 2 hours.

17. The method of claim 16, wherein, after aging, the ribbon comprises an oligocrystalline microstructure having columnar grains extending across the thickness of the ribbon, wherein the columnar grains are separated by intergrain nodes and wherein the columnar grains each comprise a grain width, the grain width being at least twice the thickness.

18. The method of claim 16, wherein the ribbon exhibits an induced magnetic moment of at least 1 emu/g in an applied magnetic field of 30 kOe.

19. The method of claim 16, wherein the ribbon exhibits a latent heat of martensitic transformation of at least 5.0 J/g.

20. The method of claim 16, wherein the ribbon comprises an elastic modulus of at least 10 GPa.

21. The method of claim 16, wherein the ribbon comprises a yield strength (.sub.0.2) of at least 50 MPa.

22. The method of claim 16, wherein the ribbon comprises a critical transformation stress of at least 50 MPa.

23. The method of claim 16, wherein the ribbon comprises an ultimate tensile strength of at least 200 MPa.

24. The method of claim 16, wherein the ribbon comprises a total strain before failure of at least 5%.

25. The method of claim 14, wherein the copper alloyed with aluminum and manganese comprises a formula of Cu.sub.72Al.sub.xMn.sub.y, where x=175, and y=115.

26. The method of claim 14, wherein the copper alloyed with aluminum and manganese further comprises up to 5 at % of a metal selected from a group consisting of Ni, Ag, Au, Zn, Sn, Ti, Cr, Fe, Co, Si, and combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee.

[0037] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0038] FIG. 1 is a schematic representation of a melt-spinning apparatus for melt- spinning a ribbon of CuAlMn elastocaloric material, according to an exemplary embodiment;

[0039] FIG. 2 is a photograph of melt-spun CuAlMn ribbon with an inset photograph of the ribbon wound onto a cylinder, according to an exemplary embodiment;

[0040] FIG. 3 is a longitudinal cross-sectional SEM image of the CuAlMn ribbon, showing columnar grains across the thickness, in the as-spun state, according to an exemplary embodiment;

[0041] FIG. 4 is a longitudinal cross-sectional SEM image of the CuAlMn ribbon, showing a bamboo grain structure, in the heat-treated state, according to an exemplary embodiment;

[0042] FIG. 5 is a stress-strain diagram for ribbons in the as-spun state and in an aged state, according to exemplary embodiments;

[0043] FIG. 6 is a graph of the induced magnetic moment in the CuAlMn ribbon as a function of applied magnetic field for ribbons in various stages of aging treatment, according to exemplary embodiments;

[0044] FIG. 7 are DSC curves for CuAlMn ribbon samples showing martensitic transformation characteristics based on different heat treatments, according to exemplary embodiments;

[0045] FIG. 8 depicts DSC curves for the CuAlMn ribbon having been spun, annealed and aged for 5 minutes, demonstrating the reversibility of the martensitic transformation through 6 heating and cooling cycles, according to an exemplary embodiment;

[0046] FIGS. 9-11 depict thermal imaging pictures of a CuAlMn ribbon before loading (FIG. 9), after loading (FIG. 10), and upon unloading (FIG. 11), demonstrating the elastocaloric effect, according to an exemplary embodiment;

[0047] FIG. 12 depicts a plot of temperature change as a function of tensile strain for loading and unloading of the CuAlMn ribbon, according to an exemplary embodiment;

[0048] FIG. 13 depicts a cloth, in particular a woven cloth, including a CuAlMn ribbon among yarns of other fibers, according to an exemplary embodiment; and

[0049] FIG. 14 is a graph representing the range of reported values of endothermic latent heat during the martensite to austenite transition, L.sub.M.fwdarw.A, for typical elastocaloric materials.

[0050] While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0051] CuAlMn alloys display martensitic transformation over a wide range of temperatures. In addition to low cost, this alloy is known for its low transformation stress with reasonable latent heat favoring elastocaloric applications. However, the ductility of CuAlMn can be limited owing to ordering and intergranular fracture. Through rapid solidification by melt spinning, Applicant has demonstrated that CuAlMn ribbon can be made highly ductile (greater than 8% tensile strain in the as-spun state and 10% tensile strain after heat treatment). The ductility of the melt-spun ribbon is related to the suppression of L2.sub.1 ordering that is characterized through magnetic property measurement. Heat treatment of the ribbon promotes bamboo grain formation, and the latent heat is increased to 6.4 J/g. Under tensile conditions, embodiments of the presently disclosed CuAlMn ribbon exhibited about 4 C. temperature change (4.4 C. on heating and 4.2 C. on cooling) from 6.3% strain. These and other aspects and advantages of the disclosed elastocaloric CuAlMn ribbon will be described more fully in relation to the embodiments presented below and in the figures. These embodiments are presented by way of illustration and not limitation.

[0052] Embodiments of the present disclosure relate to a ribbon 100 of an elastocaloric material. In one or more embodiments, the elastocaloric material comprises copper (Cu), aluminum (Al), and manganese (Mn). In one or more embodiments, the elastocaloric material has the formula of Cu.sub.72Al.sub.xMn.sub.y, where x=115, and y=175. Minor alloying elements may also be added to the material system, such as Ni, Ag, Au, Zn, Sn, Ti, Cr, Fe, Co, and Si in a combined amount of up to 5 at %.

[0053] As shown in FIG. 1, the ribbon 100 is produced using a melt-spinning apparatus 110. The apparatus 110 includes a crucible 120 that contains an elastocaloric material feedstock 130. Disposed around the crucible 120 is a heating element 140, such as an inductive heating element, among other possibilities. The heating element 140 is configured to melt the elastocaloric material feedstock 130, and the molten elastocaloric material feedstock 130 is forced through a nozzle 150 of the crucible 120 as a stream 160 of molten elastocaloric material. In one or more embodiments, the molten elastocaloric material feedstock 130 is forced through the nozzle 150 using pressurized gas, such as an inert gas (e.g., argon).

[0054] The stream 160 is directed onto a spinning wheel 170. As shown in FIG. 1, the wheel is depicted as rotating, which allows the stream 160 to contact an uncovered surface of the wheel 170. In this way, the surface of the wheel 170 immediately cools the stream 160 of molten elastocaloric material to produce the solidified ribbon 100 of elastocaloric material. To facilitate cooling, in one or more embodiments, the wheel 170 is cooled with a fluid, such as water. In one or more embodiments, the wheel 170 is rotated at a speed of at least 3 m/s (tangential speed), in particular at a speed of at least 10 m/s (tangential speed). The degree of cooling is dependent, at least in part, on the length of time that the stream/ribbon 160/100 is in contact with the outer surface of the wheel 170. In one or more embodiments, the ribbon of elastocaloric material is in contact with the outer surface of the rotating wheel 170 over an arcuate distance (D) of at least 25 mm. In one or more embodiments, the rotating wheel has a diameter of about 250 mm or more. In one or more embodiments, the ribbon 100 of elastocaloric material is in contact with the rotating wheel 170 for at least 5 of rotation (as denoted by rotation angle in FIG. 1). Advantageously, the molten elastocaloric material cools at a rate on the order of 10.sup.6 C./s, which allows the elastocaloric material to substantially or fully suppress the ordering transition A2-B2-L2.sub.1 and refines the microstructure to contribute to well-balanced strength and ductility.

[0055] In one or more embodiments, the melt-spun ribbon 100 of clastocaloric material is further annealed. In one or more such embodiments, the annealing takes place at a temperature in a range from 600 C. to 1100 C. for a time of 5 minutes to 10 hours. Further, in one or more embodiments, the annealed ribbon 100 is quenched, e.g., in brine ice water. In one or more embodiments, the melt-spun and annealed ribbon 100 of elastocaloric material is aged. In one or more such embodiments, the aging is performed at a temperature in a range of 50 C. to 500 C. for a time of 1 minute to 2 hours. Further, in one or more embodiments, the aging may be performed in air. As will be discussed more fully below, the aging process may be used to tune certain properties of the melt-spun ribbon 100, such as its magnetic properties.

[0056] In one or more embodiments, the ribbon 100 exhibits an ultimate tensile strength of at least 200 MPa, in particular at least 300 MPa, and most particularly up to about 350 MPa. In one or more embodiments, the ribbon 100 exhibits a yield strength (60.2) of at least 50 MPa, in particular at least 100 MPa. In one or more embodiments, the ribbon 100 exhibits a critical transformation stress of at least 50 MPa. In one or more embodiments, the ribbon 100 exhibits an elastic modulus of at least 10 GPa, in particular at least 11 GPa. In one or more embodiments, the ribbon 100 exhibits a tensile ductility (i.e., total tensile strain before failure) of at least 5%, in particular at least 8%, and most particularly up to about 15%. The ribbon 100 exhibits mechanical properties far exceeding the properties reported in the literature for CuAlMn alloys (typically 100-200 MPa yield strength and less than 10% tensile strain).

[0057] In one or more embodiments, the ribbon 100 exhibits an oligocrystalline, or bamboo, microstructure in which narrow crystalline nodes separate wide columnar, internodal crystal grains. Such structure can be seen and will be more fully described below in relation to FIG. 4. In one or more other embodiments, the ribbon 100 exhibits a microstructure containing columnar grains in which a width of the grains (dimension extending into the depth of the ribbon) is more than the height (in the thickness direction) of the columnar crystal as can be seen and will be more fully described below in relation to FIG. 3.

[0058] In one or more embodiments, the ribbons 100 produced via melt-spinning have a thickness (dimension of ribbon 100 perpendicular to the outer surface of the wheel 170) of 0.1 mm or less, in particular in a range from 0.01 mm to 0.1 mm. The thickness of the ribbon 100 can be controlled, e.g., based on the speed of the spinning wheel 170 and the rate of flow of the stream 160 of molten elastocaloric material. In one or more embodiments, the ribbons 100 have a width in a range from 0.1 mm to 300 mm. Commercially, melt-spun ribbons 100 are typically produced having widths of about 50 mm or about 250 mm. Further, in one or more embodiments, the ribbons 100 may be melt-spun to lengths up to 1000 m. While not particularly limited, the ribbons 100 typically have a length of at least 10 m when produced via melt-spinning.

[0059] In one or more embodiments, the ribbon 100 produced via melt-spinning, after having been annealed, quenched, and aged, exhibits an induced magnetic moment of at least 1 emu/g, in particular at least 3 emu/g, and most particularly at least 5 emu/g, in an applied field of 30 kOe.

[0060] In one or more embodiments, the ribbon 100 produced via melt-spinning exhibits a latent heat for martensitic transformation of at least 5 J/g, in particular at least 6 J/g. In one or more embodiments, the ribbon 100 exhibits a thermal hysteresis for austenite finishing temperature (Af)-martensite finishing temperature (Mf) in a range of about 1 C. to about 100 C., in particular about 55 C. Further, in one or more embodiments, the ribbon 100 produced via melt-spinning exhibits a change in temperature of at least 4 C. when loaded to or unloaded from a tensile strain of about 6%.

Experimental Example

[0061] An ingot of Cu.sub.72Al.sub.17Mn.sub.11 (nominal composition in at. %) was prepared by arc melting of elemental Cu, Al, Mn chunks (>99.9%) acquired from the Materials Preparation Center at Ames National Laboratory. The alloy ingot was melt spun to ribbons using a custom-built melt spinner with a vacuum chamber partially filled with of ultra-high purity helium. The melt spinner included a quartz crucible nozzle having a diameter of 0.81 mm. Further, the melt spinner melt shot temperature was 1150 C., and the overheat pressure was 120 Torr. The copper wheel had a diameter of 25 cm, a width of 2.5 cm, and rotated at a speed of 30 m/s. The melt-spun strip was annealed in a helium-filled quartz ampule at 900 C. for 2 hours, followed by quenching in brine ice water. The melt-spun and annealed ribbon was subsequently aged at 200 C. in air.

Microstructure

[0062] FIG. 2 is a photograph of a collection of ribbons after the melt-spinning process. The ribbon has a width of 1 mm and a thickness of 20-30 m, controlled mainly by nozzle size and wheel speed. The ribbon is continuous (tens of meters long) with excellent surface quality, and as shown in the inset of FIG. 2, the ribbon can be wound onto a cylinder.

[0063] Cross-sectional microstructures (along the ribbon length direction) of the ribbons were analyzed using Scanning Electron Microscope (SEM) (Teneo, FEI Inc) equipped with Energy Dispersive X-ray Spectroscopy (EDS) detector. The ribbons were mounted on their side and polished and etched with 5% nital prior to imaging. FIG. 3 depicts the as-spun ribbon, which exhibits a columnar grain microstructure with the grains aligned substantially parallel to the thickness direction (T). Such columnar gain microstructure is commonly observed in melt-spun ribbons as it follows the heat extraction from the wheel side to the free side of the ribbon. However, the as-spun ribbon does not show any stress-induced martensitic (SIM) transformation at room temperature, presumably because of the large quench in vacancy density and unstable martensite formation (see discussion below relative to the DSC analysis). To facilitate SIM, the ribbon was annealed and aged. The heat treatment resulted in significant recrystallization, grain growth, and the formation of oligocrystalline grains as shown in FIG. 4. The height of the grains extends to the ribbon's full thickness (T), while the length (L) of the grains is about 3-4 times the ribbon's thickness (T). In this way, the grains of the ribbon highly resemble the cellular structure seen in bamboo in which nodes separate internodal grains. EDS confirmed the composition of the ribbons, and it matched the nominal composition.

Tensile Properties

[0064] Tensile tests were conducted using a universal testing machine (Zwick/Roell, zwickiLine) equipped with a laser extensometer using a strain rate of 110.sup.3 s.sup.1 on a single ribbon. Each of the samples tested was pre-loaded at 50 MPa. The as-spun ribbon exhibited a yield strength (YS) of about 400 MPa, and tensile ductility of at least 8% as in FIG. 5. Failure of the as-spun ribbon was likely due to defects in the ribbon.

[0065] FIG. 5 demonstrates that the SIM transformation has been activated for the ribbon after heat treatment for the Aged_1 and Aged_2 ribbon samples. The Aged_1 sample was strained to fracture, and the Aged_2 sample loaded to 5% strain and unloaded. The stress for SIM transformation, which depends on austenite finishing temperature according to the Clausius-Clapeyron relation, for the ribbon is approximately 120 MPa matching what is typically reported for this alloy composition.

[0066] Due to the pre-load applied to the ribbon necessary for accurate laser strain measurement, quantifying the recoverable strain for the Aged_2 sample is difficult. Still, the recoverable strain is at least 4% out of the 5% total strain applied to the Aged_2 sample. As can be seen with respect to the Aged_1 sample, after the stress plateau for the SIM, there is some work hardening before the ribbon fractures. Because of the superelastic strain accommodated by the martensitic reorientation, the Aged_1 sample showed much higher tensile strain (10%) before failure than for the as-spun sample. The order-disorder transition between A2-B2-L2.sub.1 in Cu.sub.72Al.sub.17Mnn is known to significantly affect the ductility of the alloy. Thus, by suppressing the ordering transition, the ductility is improved.

Magnetic Properties

[0067] The magnetic moment of the ribbon was measured with Vibrating Sample Magnetometer (VSM) (Versalab, Quantum Design, Inc.). The L2.sub.1 (Cu.sub.2AlMn) phase is a Heusler compound with unique ferromagnetic properties while the other two phases (A2 and B2) are paramagnetic. VSM measurement characterizing the magnetic properties is, therefore, instrumental for evaluating the ordering degree. FIG. 6 depicts the magnetic moment induced in ribbon strips based on applied magnetic field for ribbon strips annealed at high temperature, water quenched, and aged for 0 minutes/hours (as-spun), 1 minute, 5 minutes, 30 minutes, 3 hours, 6 hours, 12 hours, and 24 hours. From FIG. 6, it can be seen that the as-spun ribbon is paramagnetic, confirming the disordered structure. Aging treatment between 1 minute to 30 minutes decreases the magnetic susceptibility of the paramagnetic alloy. Paramagnetic L2.sub.1 is known to form before the ferromagnetic L2.sub.1 forms the disordered structure. Therefore, paramagnetic L2.sub.1 likely formed in the samples that were aged under 30 minutes. From FIG. 6, it can be seen that the paramagnetic L2.sub.1 phase has a smaller magnetic susceptibility than its parent disordered phase. The magnetic susceptibility surpasses the as-quenched ribbon after 3 hours of 200 C. aging, and the ribbons become highly ferromagnetic after aging for 6 hours suggesting strong ferromagnetic L2.sub.1 order.

Phase Transformation Characteristics

[0068] The phase transformation characteristics of the samples were measured by differential scanning calorimetry (DSC) (Netsch DSC 214 Polyma) on ribbon pieces from 150 to 150 C. with a heat/cool rate of 10 C./min. FIG. 7 shows the transformation characteristics for the ribbon sample after different heat treatments. The as-spun ribbon (AS curve) exhibits no martensitic transformation in the current measurement temperature range. As reported in the literature, a drop in martensite start (Ms) temperature can be significant when the cooling rate is 2500 C./s. This is because large amounts of clustered quench-in vacancies form during quenching, and they are pinned to partial dislocations hindering the nucleation of martensite. In contrast, the cooling rate of melt spinning is 10.sup.6 C./s, three orders of magnitude higher than 2500 C./s. Therefore, the suppression of Ms can be tremendous in the melt-spun ribbon. Subsequent 200 C. aging treatments without 900 C. annealing for the as-spun ribbon have minimum impact on the martensitic transition (AS_200C10min and AS_200C20h curves).

[0069] The effect of annealing and quenching on the ribbon is evident, and it brings the transition above 150 C. as shown on the DSC curve labeled as AS_ANQ in FIG. 7. Aging treatment at 200 C. for 1 minute decreases the quench-in vacancy densities and results in some increase in the transition temperature (AS_ANQ_1 m curve). An increase in the aging temperature from 1 minute to 5 minutes has resulted in a stabilized martensitic transformation near room temperature (AS_ANQ_5 m). The latent heat of the 200 C. 5-minute aged ribbon is 6.4 J/g. In comparison, the latent heat was reported to be 4.8 J/g on a single crystal Cu.sub.72Al.sub.17Mn.sub.11 alloy, and 6.4 J/g on a directional solidified Cu.sub.71.5Al.sub.17.5Mn.sub.11 alloy. This suggests columnar or bamboo grain may be responsible for higher latent heat. Aging at 200 C. for a longer time tends to decrease the latent heat because of ordered phase formation, as confirmed by the VSM measurement discussed above (see curves AS_ANQ_200C10m, AS_ANQ_200C30m, and AS_ANQ_60m). Once the ribbon becomes fully ordered with strong ferromagnetism (200 C., 6 h aging; AS_ANQ_200C6h curve), it does not show any martensite transformation. A second peak was observed above 100 C. for ribbon aged for longer than 10 minutes, which can be correlated to the Curie point for the ferromagnetic L2.sub.1 phase as reported for similar compositions.

[0070] The reversibility of the martensitic transformation was confirmed on the 200 C., 5 min aged ribbon as shown in FIG. 8. As can be seen there, the martensitic transition is mostly stabilized after the first heating and cooling cycle. There is still some shift in the transition temperatures in the subsequent cycles, but the magnitude of the shift decreased for each successive cycle. The thermal hysteresis, austenite finishing temperature (Af)martensite finishing temperature (Mf) is about 55 C. for this ribbon under the current heat treatment conditions.

Elastocaloric Properties

[0071] Temperature changes under tensile loading/unloading at ambient temperature were measured on a single aged ribbon using a custom-built device. In particular, the strain of the ribbon was measured with a displacement sensor at the grip, and the temperature of the ribbon was measured by an infrared camera (FLIR A8303sc) to determine the elastocaloric effect of the ribbon. The ribbon was sprayed with matte dark paint to enhance thermal emissivity for infrared thermography and pre-loaded into the tensile grip to ensure it is fully stretched before loading. FIG. 9 depicts a heat map of the pre-loaded ribbon as captured by the infrared camera. As can be seen, the temperature of much of the ribbon and its surroundings are substantially the same, in particular differing by less than about 1 C. (in the range of 21.0 C. to 21.8 C.).

[0072] FIG. 10 shows that the ribbon becomes hotter than the surroundings when loaded. In particular, the thermal imaging of FIG. 10 shows that the ribbon, when loaded to a strain of 6.3%, heated to a temperature of about 25 C., whereas the surroundings remained at a temperature below about 22 C. FIG. 11 shows that the ribbon becomes cooler than the surroundings when unloaded (i.e., relaxed from the loaded state). The thermal imaging of FIG. 11 shows that the ribbon, when relaxed from the loaded state, cools to a temperature below 19 C. Thus, the ribbon clearly exhibits an elastocaloric effect from loading and unloading. Further, the inventors observed that the temperature changes in the loading and unloading states increased with higher strain. The highest temperature change recorded by the inventors on this ribbon was 4.4 C. on loading and 4.2 C. on unloading from a 6.3% strain before it fractures at 7%. Such temperature change is higher than the value (3.9 C.) reported on a single-crystalline Cu.sub.72Al.sub.17Mn.sub.11 alloy under compression. However, it is much lower than the adiabatic temperature change of 12.8 C. reported for a columnar-grained directional solidified Cu.sub.71.5Al.sub.17.5Mn.sub.11 alloy which was tensile strained (under a fast strain rate of 1.310.sup.1 s.sup.1) to 10%.

[0073] FIG. 12 provides a plot of the temperature change as a function of tensile strain. As can be seen, the temperature change increases with increasing tensile strain. In particular, the temperature change increases substantially linearly with increasing tensile strain for both loading and unloading.

[0074] The adiabatic limit for the temperature change T achievable is estimated by T =L/Cp, where L is the latent heat, and C.sub.p is the heat capacity. Using L=6.4 J/g from the DSC results discussed above and C.sub.p=0.44 J/g.Math. C. at 20 C. as determined by Physical Property Measurement System (PPMS, DynaCool, Quantum Design), the T is expected to be 14.5 C. This theoretical T is significantly higher than other elastocaloric materials except for NiTi.

[0075] In view of the theoretical limit of 14.5 C. for temperature change, the inventors surmise that the current tensile demonstrations only unleashed 30% of this potential for two reasons. First, the experimental setup had poor adiabatic conditions. Further, the strain rate (310.sup.2 s.sup.1) was not optimized, and the elastocaloric test is highly strain rate dependent, where a higher T is correlated with a higher strain rate. There may also be significant ambient heat loss due to the large surface area of the ribbon sample. Second, the ribbon may have some thickness variation and defects (though it can be optimized through melt spinning process control), which prevents sufficient strain loading for a complete transition. Further, the heat treatment of the ribbons used in the tensile and elastocaloric experiments was not optimized, and there could have been a large energy dissipation W due to the friction at the residual untransformed austenite/martensite interface. Using

[00001]$\begin{array}{cc}W=\left(\right)d/& \left(1\right)\end{array}$

where the density =7.4103 kg/m.sup.3, and the hysteresis loop area

[00002]$\left(\right)d=3.5$

10.sup.6 J/m.sup.3 according to FIG. 5, the dissipation heat W is calculated to be 473 J/kg.

[0076] This results in an irreversible temperature change because of heat dissipation T.sub.dis=0.54 C. according to the following equation, where Cp=0.44 J/g. C.

[00003]$T_{\mathrm{dis}}=W/2C_p$

[0077] This heat dissipation can be significant as it increases with larger strains, mainly due to the large hysteresis loop. The inventors expect that optimized heat treatment should minimize the stress-strain hysteresis and reduce the internal friction energy loss.

Flexibility and Softness Properties

[0078] In addition to space cooling application using its elastocaloric potential, the CuAlMn ribbon may also be used for shape memory smart cloth as it is highly flexible and soft. To quantify the softness of our ribbon, we compare the tensile stress-strain curve against that of the wool. The key quantifiable quantities are elastic modulus (E), yield strength (.sub.0.2), ultimate tensile strength (UTS), and total strain before failure (<>). The rapidly solidified ribbon is strong and tough. After aging, the CuAlMn metal ribbon is much more flexible (see FIG. 5, Aged_1 curve). It exhibits an elastic modulus (E) of 11.3 GPa, a yield strength (.sub.0.2) of around 115 MPa, an ultimate tensile strength (UTS) of 342 MPa, and a total strain before failure (<>) of 10.3%. As reported in the literature, wool fibers obtained from sheep show very similar behavior. The reported values for the wool are E=3.930.61 GPa, .sub.0.2 =142.830.3 MPa, and <>=25.911.4%. Table 1, below, provides a comparison of the tensile properties.

TABLE-US-00001 TABLE 1 Comparison of Tensile Properties of Aged CuAlMn ribbon with Wool Fiber Ultimate Total Strain Elastic Yield Tensile Prior to Modulus Strength Strength Failure (E) (.sub.0.2) (UTS) (<>) GPa MPa MPa % Aged 11.3 115 342 10.3 CuAlMn ribbon Wool fiber 3.93 0.61 142.8 30.3 N/A 25.9 11.4

[0079] In one or more embodiments, at least one CuAlMn elastocaloric ribbon is incorporated into a cloth. The cloth may be formed predominantly of or entirely of the CuAlMn elastocaloric ribbon. The cloth may include yarns of other materials, such as animal fibers (e.g., wool, alpaca, angora, mohair, cashmere, silk, etc.), plant fibers (e.g., cotton, linen, silk, bamboo, hemp, etc.), and/or synthetic fibers (e.g., nylon, acrylic, rayon, polyester, spandex, etc.). In one or more embodiments, the cloth is a woven cloth. In one or more such embodiments, ribbons of the CuAlMn elastocaloric material are woven together or with one or more of the yarns of other materials to form the woven cloth. In one or more embodiments, the cloth is non-woven, and the yarns of one or more of the other materials may be tangled, bonded, glued, or otherwise joined to form a fabric into which the CuAlMn is tangled, bonded, glued, sewn, or otherwise joined. In one or more embodiments, the cloth is a knit fabric, and ribbons of the CuAlMn elastocaloric material are knitted together or with the yarns of one or more of the other materials. In one or more embodiments, the cloth comprising the CuAlMn elastocaloric ribbon is at least one layer in a laminate structure.

[0080] FIG. 13 depicts an embodiment of a cloth 200, in particular a woven cloth, incorporating one or more ribbons 210 of the CuAlMn elastocaloric material among yarns 220 of other fibers. In one or more embodiments, the cloth 200 can be used to create clothing, blankets, coverings, shelters, medical supplies, sails, storage bags, upholstery, nets, filters, and geotextiles, amongst other possibilities. In one particular application, a cloth woven from ribbons of CuAlMn material can be used as an actively controlled filter in which the porosity is

[0081] Additionally, the CuAlMn ribbons can also be heat treated to render a range of different tensile properties (i.e., softness), as exemplified by the vastly different behavior between the As-spun curve and Aged_1 curve in FIG. 5.

[0082] In sum, the foregoing disclosure describes the melt spinning of strong and highly ductile continuous CuAlMn ribbons. The ribbon has a favorable columnar grain structure in the as-spun state and is transformed into a bamboo grain structure after heat treatment. The rapid solidification inherent to melt spinning suppressed the deleterious order-disordered transition responsible for the alloy's brittleness. The martensitic transformation is temporally suppressed in the melt-spun ribbon but can be reactivated by annealing and aging. Heat-treated ribbons exhibited the highest latent heat of 6.4 J/g of the ribbons produced, which is much higher than what is typically reported (4-5 J/g) for this alloy composition. Such latent heat is expected to deliver 14.5 C. temperature change under adiabatic conditions, optimal strain rate, and optimized heat treatment. Experimentally, the ribbon demonstrated (though under less than ideal adiabatic and non-optimized heat treatment conditions) a temperature change of 4.4 C. on loading and 4.2 C. on unloading, showing great potential for low-cost elastocaloric applications.

[0083] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0084] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0085] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.