NANOPOROUS ALLOYS

Abstract

The disclosure relates to nanoporous alloys, and methods to prepare them.

Description

BACKGROUND

Nanoporous metallic materials offer a high surface-area-to-volume ratio, low specific weight, and very high strength. However, they remain brittle at the macroscopic scale. The brittleness of nanoporous metallic materials is currently a huge hurdle to their development and deployment but may be partially suppressed using high-entropy alloys, which may increase the strength of the weakest ligaments.

Nanoporous metallic materials have been successfully synthesized by dealloying, including nanoporous-Cu materials from Cu_xMn_1-x[Hay⁰⁶, Min⁹⁴] and Cu_xZn_1-x[Pic⁶⁷, Pry⁸⁴] precursors, nanoporous-Au materials from Au—Ag alloys [Bie⁰⁵, For⁸⁰, For⁸¹, Hod⁰⁹, Sun^08a], nanoporous-Cu materials from Ni_xCu_1-x[Sun⁰⁴], and nanoporous-Pt systems from Pt_0.25Cu_0.75 [Pug⁰³]. Depending on the initial alloy composition, dealloying rate, type of electrolyte, and annealing process, this technique can tailor the ligament pore size [Sek⁰⁷, Sek⁰⁸]. Although the dealloying process can induce crack formation in nanoporous metallic materials, the process has been greatly improved to minimize crack formation using gentle dealloying [Jin09] or stepped potential techniques [Sun^08b]. More recently, two techniques have been developed to further improve the stability of nanoporous structures: (i) the vapor-phase dealloying method used to fabricate nanoporous-Co materials from Co₅Zn₂₁ by utilizing the vapor pressure difference between Co and Zn; this process selectively removes Zn, which has a higher partial vapor pressure than Co [Lu¹⁸]; and (ii) the liquid metal dealloying and the electrochemical dealloying methods, both based on the control of microstructure and morphology through the relative magnitudes of interfacial/surface diffusion and dissolution rates [McC¹⁸].

A problem of nanoporous metallic materials seems to come not from microscopic brittleness but rather from the macroscopic network of the structure. When one ligament experiences a catastrophic failure, the adjacent ligaments are mechanically weakened by increasing their stress, and trigger a failure cascade of ligaments. It is then important to reduce the stress by suppressing the crack nucleation sites. Some experiments attribute the brittleness to stress-corrosion cracking [Fri⁹⁶, Kel⁹¹, Sie⁸⁵], tensile stress during dealloying [Liu⁰⁶, Par⁶, Sen⁰⁶] surface segregation during annealing [Mei⁸⁸], void-like defects that can be observed along the original GBs [Bie⁰⁷], and dangling ligaments [Jin¹⁸].

Nanoporous high entropy alloys (Al_4.7Cr_41.1Fe_27.1Co_20.2Ni_6.8 (at %) and Ta_19.1Mo_20.5Nb_22.9V₃₀Ni_7.5 (at %) have already been fabricated to study their catalytic performance [Kim¹⁹, Oku²⁰]. However, the ligament size was in the range of 30-70 nm. The mechanical properties of nanoporous high entropy alloys have been studied [Zhang, K], [Zhang, K]. Their remarkable properties will depend on the fabrication process and the ligament size:

Thus, despite advances in nanoporous alloy research, there is still a scarcity of materials that have very high strength, minimal ligament sizes, and minimized cracking, e.g., crack nucleation. These needs and other needs are met in whole or in part by the present disclosure.

SUMMARY

The disclosure, in one aspect, includes a nanoporous alloy prepared by a process comprising: (i) admixing at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu), with a sacrificial element selected from the group consisting of lead (Pb), tin (Sn), magnesium (Mg), and bismuth (Bi);

• • wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;
  • wherein each of the at least three different elements independently has an average particle size of from 10 nm to 500 nm as measured by dynamic light scattering;
  • (ii) heating the resulting admixture to an elevated temperature of from about 800° C. to about 2500° C. at atmospheric pressure for a period of time to provide a precursor alloy; and
  • (iii) dealloying the precursor alloy to remove the sacrificial element to provide a nanoporous alloy wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a bulk alloy comprising the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

The disclosure also includes a nanoporous alloy prepared by a process comprising: (i) admixing at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu); wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0; wherein each of the at least three different elements independently has an average particle size of from 10 nm to 500 nm as measured by dynamic light scattering;

• • (ii) heating the resulting admixture to an elevated temperature of from about 800° C. to about 2500° C. at atmospheric pressure to provide a precursor alloy;
  • (iii) admixing the precursor alloy at atmospheric pressure and temperature with a sacrificial element in a liquid state, wherein the sacrificial element is selected from the group consisting of lead (Pb), tin (Sn), magnesium (Mg), and bismuth (Bi), to produce a second admixture; and
  • (iv) dealloying the second admixture to remove the sacrificial element to provide a nanoporous alloy wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a bulk alloy comprising the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure

The disclosure also includes a continuous nanoporous alloy comprising at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu); wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0; wherein the continuous nanoporous alloy comprises an average ligament size of about 3 nm to about 100 nm when measured by SEM, TEM, and/or small angle neutron scattering

and wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a reference specific strength of a bulk alloy comprising the same at least three different elements in the same molar equivalents except without the continuous nanoporous structure.

In a non-limiting aspect, scanning electron microscopy (SEM) or transmission electron microscopy (TEM). TEM can be utilized to visualize the material and measure the ligament size directly. This requires careful sample preparation to obtain high-quality images and accurate measurements. It is important to note that the resolution of the microscope used can affect the accuracy of the measurements, and it can be necessary to use advanced imaging techniques, such as high-resolution TEM or scanning transmission electron microscopy (STEM), to obtain more precise measurements.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects of the present disclosure will be readily appreciated upon review of the detailed description of its various aspects, described below, when taken in conjunction with the accompanying drawings.

FIG. 1 is the weight-normalized Young's modulus and yield strength for different classes of materials including bulk materials and nanoporous materials¹⁵. The red circle denotes the general phase space occupied by single-component nanoporous materials based on available data. The red box represents the nanoporous HEA Al_0.1CoCrFeNi and the blue box represents the nanoporous HEA NbMoTaW, highlighting their distinctive values in specific strength and specific modulus.

FIGS. 2A-2E are the simulation boxes of the HEA Al_0.1CoCrFeNi systems for (FIG. 2A) single crystalline, (FIG. 2B) 30 nm polycrystalline, and nanoporous Al_0.1CoCrFeNi with relative densities of 28.7 (FIG. 2E), 47.8 (FIG. 2D), and 67.2% (FIG. 2C).

FIGS. 3A-3D are the stress-strain behavior of the studied HEA systems: (FIG. 3A) Compression vs tension stress-strain curves obtained from nanoporous Al_0.1CoCrFeNi samples at 600 K compared to fully dense SC and NC (20 nm) test samples; (FIG. 3B) Effect of ligament diameter and density of nanoporous Al_0.1CoCrFeNi samples on compressive stress-strain behavior, (FIG. 3C) Effect of temperature on compression behavior of Al_0.1CoCrFeNi, (FIG. 3D) Comparison of compression behavior of Al_0.1CoCrFeNi and NbMoTaW at 600 K.

FIGS. 4A-4L are the snapshots of the fracture process of a 4.29 nm ligament from a nanoporous Al_0.1CoCrFeNi HEA sample (28.9% relative density) under tensile testing: (FIGS. 4A,4B,4C) surface solid mesh outlining the atomic surface, (FIGS. 4D,4E,4F) dislocations (marked in red) in the ligament, (FIGS. 4G,4G,4I) twin boundaries, and (FIGS. 4J,4K,4L) stacking faults. The strain values represented in the first, second, and third column are 22.5%, 26.25%, and 31.25%, respectively.

FIGS. 5A-5D are the representative fracture process of the 28.0% relative density nanoporous NbMoTaW with 3.83 nm ligaments under tensile stress. The small spheres represent surface atoms and the larger spheres in the interior represent atoms in a defect structure. The strain values are 14% (FIG. 5A), 15% (FIG. 5B), 18% (FIG. 5C), and 20% (FIG. 5D).

FIGS. 6A-6F are the dislocation (left) and stacking fault densities (right) vs strain for various Al_0.1CoCrFeNi systems: (FIGS. 6A,B) defect density vs. compressive strain for NC and NP Al_0.1CoCrFeNi systems at 600 K; (FIGS. 6C,D) defect density vs. strain for compression at 600 K and 1273 K; (FIGS. 6E,F) defect density vs. strain for compression and tension at 600 K.

FIG. 7 is the potential energy landscape in units of eV per unit length of a/2<111>{110}edge dislocation in NbMoTaW and W. It is analyzed in both single crystal and 5 nm ligament diameter configurations.

FIG. 8 Stress vs. Relative Density of different nanoporous materials. These include nanoporous Al_0.1CoCrFeNi, NbMoTaW, Au 5,62-64, Cu 65, Pt 66,67, Ag 68, Ni 74, TiO₂69, Au/Ag 70, Cu/Zr 71, and W 61.

FIGS. 9A-9F are the stress strain curves of Al_0.1CoCrFeNi systems under compression at (FIG. 9A) 298 K, (FIG. 9B) 600 K, (FIG. 9C) 1273 K and tension at (FIG. 9D) 298 K, (FIG. 9E) 600 K, (FIG. 9F) 1273 K. NC represent nanocrystalline systems.

FIGS. 10A-10F are stress strain curves of NbMoTaW systems under compression at (FIG. 10A) 298 K, (FIG. 10B) 600 K, (FIG. 10C) 1273 K and tension at (FIG. 10D) 298 K, (FIG. 10E) 600 K, (FIG. 10F) 1273 K. NC represents nanocrystalline systems.

FIGS. 11A-11D are the dislocation concentration vs strain at 600 K (FIG. 11A)/1273 K (FIG. 11B) and stacking fault concentration vs. strain at 600 K (FIG. 11C)/1273 K (FIG. 11D) for the Al_0.1CoCrFeNi HEA systems under compression. Nanocrystalline systems are shown as dashed curves.

FIGS. 12A-12D are the dislocation concentration vs strain at 600 K (FIG. 12A)/1273 K (FIG. 12B) and stacking fault concentration vs. strain at 600 K (FIG. 12C)/1273 K (FIG. 12D) for the Al_0.1CoCrFeNi HEA systems under tension. Nanocrystalline systems are shown as dashed curves. Note the different scale of the 1273 K plots.

FIG. 13 is the display of defect pileup in the joints of the NP Al_0.1CoCrFeNi. The image on the left shows the surface of the NP system and the image on the right displays the defects inside the ligament that shows twin boundaries and stacking faults with different colored planes. This is the 28.9% relative density 4.23 nm ligament size nanoporous Al_0.1CoCrFeNi under tensile stress at 1273 K.

FIGS. 14A-14B are the Defect Concentration vs. Strain curves for the NbMoTaW nanoporous systems that focus on dislocations at 600 K (solid line) and 1273 K (dashed line) for compression (FIG. 14A) and tension (FIG. 14B).

FIGS. 15A-15C are the internal stress of 5 nm ligament (FIG. 15A) and bulk (FIG. 15B) NbMoTaW with the heat map legend (FIG. 15C). 400 bins in the x and y direction are used to calculate the averaged stress in the z direction.

FIGS. 16A-16H are the fracture process of the 28.0% relative density 4.79 nm ligament size nanoporous NbMoTaW HEA under tensile testing. This shows the surface solid mesh outlining the atomic surface and dislocations colored red in the ligament. The strain values represented are (FIGS. 16A,B) 13.00%, (FIGS. 16C,D) 15.00%, (FIGS. 16E,F) 18.00%, and (FIGS. 16G,H) 20.00%, respectively.

FIGS. 17A-17C are simulation boxes showing the 67.2% relative density 7.33 nm Al_0.1CoCrFeNi nanoporous system under compression at 298 K. The red boxes show the locations of pore sites being reduced and ligaments connecting with strains of 0% (FIG. 17A)/25% (FIG. 17B)/50% (FIG. 17C).

FIGS. 18A-18D are surface energy vs strain of nanoporous Al_0.1CoCrFeNi for compression at 600 K (FIG. 18A)/1273 K (FIG. 18B) and tension at 600 K (FIG. 18C)/1273 K (FIG. 18D). (FIG. 18A) Only compression results 600 K, (FIG. 18B) Compression vs tension results at 600 K for SC, NC20, 28.9 den, 47.8 den, 67.2 den, (FIG. 18C) Effect of temperature between 600 and 1273 K, (FIG. 18D) different HEA systems at 600 K.

Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or can be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

DETAILED DESCRIPTION

In an aspect, single phase alloys, e.g., single phase high-entropy alloys, may have structural properties with very high strength and ductility as well as good fracture toughness. Such high-entropy alloys exhibit good corrosion and fatigue resistance. Due to the high ductility of high-entropy alloys, an aspect of the disclosure may be that nanoporous high entropy alloys outperform or surpass current nanoporous metallic materials.

As disclosed in FIG. 1, in an aspect of the disclosure, molecular dynamic simulations may validate these properties for certain alloy mixtures [Wor²²]. The specific modulus of the simulated nanoporous high entropy alloy (Al_0.1CoCrFeNi) having ligament sizes lower than 15 nm is found to be 2-3 times the value compared to single element nanoporous metallic materials, while its specific strength is found to be 5-10 times greater, reaching values that correspond with bulk metals that have the highest specific strength.

Also as disclosed in FIG. 1, the specific modulus of the simulated nanoporous high entropy alloy (NbmoTaW) having ligament sizes lower than 15 nm is found to be 2-3 times the value compared to single element nanoporous metallic materials, while its specific strength is found to be 5-10 times greater, reaching values that correspond with bulk metals that have the highest specific strength.

In an aspect, these materials can comprise 3, or 4, or 5 elements in an equimolar ratio [Yeh⁰⁴]. In an aspect, the materials can comprise at least 3 elements in a near equimolar ratio, and the mol fraction of each element lying in the range 0.05 to 0.35 (5-35%) [Tas¹³, Wan¹⁴].

In an aspect, among all the classes of high-entropy alloys, complex, concentrated alloys, and other multi-principal element alloys, high entropy alloys comprising 3d transition metals, e.g., those derived from superalloys and stainless steels, are disclosed. The principal elements are Co, Cr, Fe, and Ni, with optional addition of elements such as Al, Cu, and Mn is common. The equimolar and non-equimolar amounts of these elements have been investigated and the alloys mainly exhibit a single Face-Centered Cubic phase due to the low mixing enthalpy of the different constituents and the high atomic fraction of Face Centered Cubic stabilizing elements, namely, Co, Cu, Mn, and Ni [Can¹⁴, Cho⁰⁹, Cui¹¹, Gal¹³, Kao⁰⁹, Li⁰⁹, Li¹⁰, Lin¹¹, Luc¹³, Wan¹²].

In an aspect, the addition of Al above 10 atom % in a CoCrFeNi system can form a multi-principal element alloy with a duplex Face Centered Cubic and Body Centered Cubic structure.

The unique mechanical behavior of nanoporous metallic materials differs from their bulk counterparts due to the 3D porous structure. FIG. 1 displays the weight-normalized strength versus stiffness diagram for different materials [Gib⁹⁷], and nanoporous metallic materials lie outside the well-known regions of conventional materials. They are also stronger than bulk materials. One of the most popular nanoporous metallic materials studied so far is nanoporous-Au, because it is relatively easy to control pore size by annealing [Bie⁰⁵, Bie⁰⁶, Sek⁰⁷, Hod⁰⁷, Hod⁰⁹, Lee⁰⁷, Liu¹³, Mat⁰⁷, Sek⁰⁸, Vol⁰⁶]. Nanoporous-Pt and nanoporous-Cu have been studied extensively due to their outstanding mechanical properties [Ant⁰⁹, Hay⁰⁶, Yua¹⁴]. Nevertheless, most nanoporous metallic materials exhibit similar mechanical behavior and trends arise from these studies. The brittleness of nanoporous metallic materials is currently a huge hurdle to their development. Nanoporous high entropy alloys seem to suppress this brittleness.

In an aspect, these nanoporous alloys can comprise the properties of nanoindentation and micropillar compression. These can be used to measure mechanical properties (including yield strength and Young's modulus) in order to capture the behavior of the ligaments, while macroscopic tensile or compressive tests address the response of the nanoporous material as a whole [Bie⁰⁵, Bie⁰⁶, Hak⁰⁷, Lee⁰⁷, Vol⁰⁶]. In an aspect, the yield strength and/or the elastic modulus of nanoporous materials can be governed by their relative density and, for strength, their ligament size. As understood by a person of ordinary skill, the term relative density means the ratio of the volume of solid material to the total volume of the material.

In an aspect, strength increases dramatically with decreasing ligament size, due to mechanical size effects involving constrained dislocation motion in nanoscale ligament volumes [Hod⁰⁷]. While not constrained by any theory, the size effects due to ligaments are not reproduced by the Gibson and Ashby scaling relations, which do not consider the ligament size, but the introduction of a correction term does improve the predictive capability of such scaling relations [Bri¹⁵, Hod⁰⁷].

By contrast, increased stiffness of nanoporous metallic foams arises from surface stress and density increases, while larger bending stiffness arises from smaller ligament size [Mat⁰⁷]. In an aspect, the elastic properties of nanoporous metallic materials, however, do not evolve with the size effect. However, the crystal orientation of the ligament free surface suggests a small change [Zho^04a].

Fabrication: In an aspect, a liquid metal dealloying process can be employed to fabricate nanoporous high entropy alloys [McC¹⁶]. A liquid metal dealloying is selected based on the mixing enthalpy between the corrosive medium and the target high entropy alloy composition. Elements having a positive mixing enthalpy are immiscible in a liquid metal, while elements having a negative value of the mixing enthalpy dissolve during dealloying.

Thus, in an aspect, there are a large number of possible combinations between liquid metals and our nanoporous high entropy alloys. In an aspect, liquid magnesium (Mg). Liquid lead (Pb), liquid bismuth (Bi), and liquid tin (Sn) can be used. In an aspect, Al and Ni can partially dissolve out of the alloy while Co, Cr, and/or Fe can diffuse along the liquid/metal interface and reorganize into a bicontinous nanoporous structure. In this way, for example, nanoporous high entropy alloys Al_0.1CoCrFeNi (at %) can be fabricated from the high entropy alloy precursor Al_0.3(CoCrFe)₂₅Ni_74.7 (at %), which has a higher concentration of Ni and Al that will in part be washed out or removed. In an aspect, a precursor alloy could be Al_0.1CoCrFeNiPb (at %). Afterwards, Pb can be removed by a dealloying process.

In an aspect, the precursor alloys can be fabricated using ball milling of powders followed by a hot isostatic press or spark plasma sintering. Immediately after dealloying, the bicontinuous nanocomposite consisting of a sacrificial metal rich phase, e.g, a Mg-rich phase, and the morphology of a desired alloy, e.g., face-centered cubic, or body-centered cubic, structure of the desired high entropy alloy is formed. The Mg-rich phase is removed using an acidic aqueous solution, e.g, nitric acid, to leave the nanoporous alloy Al_0.1CoCrFeNi (at %).

In an aspect, the formation of point and extended defects during both the fabrication of the precursor and the dealloying process is minimized. A low defect concentration may reduce crack nucleation sites in the ligaments partially responsible for the often-found brittleness of nanoporous metallic materials. A thermal treatment can be applied to remove defects if necessary.

For the ligament size, diffusion of elements in high entropy alloys may be sluggish, preventing a strong coarsening of the ligaments. Thus, a slower diffusion is preferred.

In an aspect, the ligament size (in nanometers) can be about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11, about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, about 21, about 22, about 23, about 24, about 25, about 26, about 27, about 28, about 29, about 30, about 31, about 32, about 33, about 34, about 35, about 36, about 37, about 38, about 39, about 40, about 41, about 42, about 43, about 44, about 45, about 46, about 47, about 48, about 49, about 50 nm, about 51, about 52, about 53, about 54, about 55, about 56, about 57, about 58, about 59, about 60 nm, about 61, about 62, about 63, about 64, about 65, about 66, about 67, about 68, about 69, about 70 nm, about 71, about 72, about 73, about 74, about 75, about 76, about 77, about 78, about 79, about 80 nm, about 81, about 82, about 83, about 84, about 85, about 86, about 87, about 88, about 89, about 90 nm, about 91, about 92, about 93, about 94, about 95, about 96, about 97, about 98, about 99, or about 100 nm. In the foregoing array of numbers, the ligament size can be within a range from one value to another, e.g., from about 3 to about 14 nm. In an aspect, the ligament size is generally lower than about 15 nm.

Alternatively, in an aspect, the process described in [Kim¹⁹] can be employed. An as-cast AICoCrFeNi exhibiting interconnected Al—Ni and Cr—Fe rich-phases obtained from spinodal phase separation will be treated by selectively dissolving the Al—Ni rich phase while retaining the Cr—Fe rich phase by passivation in an acid solution.

Alternatively, in an aspect, the process described in Y. Xia, et al., Acta Materialia 2022, 238, 118210 can be employed. The compositions described herein can be fabricated via dealloying methods, such as electrochemical dealloying (ECD), liquid-metal dealloying (LMD), and vapor phase dealloying (VPD). In general, ECD includes selective corrosion of a sacrificed compound by an electrode potential difference across a precursor alloy. LMD, in general, includes heating up a precursor alloy to remove a sacrificial compound. The sacrificial compound is selected to have a lower phase transitioning temperature than the compounds in the desired nanoporous alloy. VPD, in general, includes subjecting a precursor alloy to high temperatures in a vacuum thereby removing a sacrificial compound. The sacrificial compound is selected to have high vapor pressure. Under the high temperature and vacuum, the sacrificial compound volatizes while the desired nanoporous alloys remain.

Alternatively, or in combination with another method described herein, in an aspect, any process described in Z. Tang, et al., Nanomaterials and Nanotechnology 2016, 6, 35 and/or T. Deng, et al., Science Bulletin 2015, 60, 304-319 can be employed. These processes include opening or tuning methods. In general, opening methods are a type of drilling method and can include, for example, ion beam, e-beam, wet etching, and anodized alumina transferring. Tuning methods, in general, refine nanopore size to the desired diameter by adding or removing parts of the alloy or changing the morphology of the nanopores. Tuning methods can include deposition or thermal treatment.

Alternatively, in an aspect, any process described in L. E. Murr, Metallogr. Microstruct. Anal. 2018, 7, 103-132, C. Han, et al., Advanced Materials 2020, 32, and/or S. Das, et al., MRS Bull. 2016, 41, 729-741. can be employed. These processes include 3D manufacturing (3DM) or additive manufacturing (AM). 3DM/AM, in general, utilizes electron and/or laser beam melting of continuous wire or powder fed compounds onto a surface for layer-by-layer fabrication of the desired nanoporous alloy. 3DM/AM can include rapid prototyping or freeform fabrication technologies. For example, 3DM/AM can include vat polymerization, material jetting, binder jetting, material extrusion, sheet lamination, powder bed fusion (PBF), laser-engineered net shaping (LENS)/direct metal deposition (DMD), and laser melting. 3DM/AM can involve CAD (computer-aided design)—controlled powder injection. The process can include surrounding the actively forming nanoporous alloy by an inert gas shroud for oxidation reduction.

Microstructural and Mechanical Characterization

Transmission Electron Microscopy and Scanning Electron Microscopy

As-cast nanoporous high entropy microstructures of nanoporous high entropy alloys can be determined by a number of methods known to those of ordinary skill in the art. For example, X-ray diffraction can be utilized to identify the crystal structures of as-cast nanoporous high entropy alloys. Scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) can be used to analyze the morphological properties and chemical composition of the nanostructures. Electron backscatter diffraction (EBSD) in SEM can be used to reveal detailed microstructures such as the phase distribution, grain boundaries, number density and shape of precipitates (if they exist), segregation, etc. For (scanning) transmission electron microscopy (TEM and STEM) investigations, electron-transparent samples can be prepared using focused ion beam or electro-polishing combined with ion milling. Bright field TEM and selected area electron diffraction (SAED) can be used to determine microstructure, including crystallographic structures, dislocations, grain structures, and pore distributions. High resolution TEM and dark field STEM can be used to characterize detailed atomic structures and elemental information. Such inquiries are usable in an iterative process to produce nanoporous high entropy alloys with the desired nanostructures [Jen¹⁶, She¹³].

In an aspect, 3D electron tomography is used to dynamically study the interaction between the dislocation and the surface. The development of the 3D electron tomography in material sciences allows for the extraction of structural information in three dimensions. However, this technique is not without difficulties. For example, Robertson needed to use two sample holders, one dedicated to the tensile stress and another dedicated for the tomography [Kac^12a, Kac^12b, Liu¹¹]. With the combination of these two holders, they were able to visualize in three dimensions the dislocation motion in stainless steels using tensile test with focused ion beam micro sampling and then tilt-series observation of the sample area. Sato and co-workers developed a new sample holder capable of performing at the same time in-situ tensile stress combined with a 3D electron tomography [Sat¹⁵]. The applied strain rates range is in between 10⁻⁶s⁻¹ and 10⁻³ s⁻¹ and the high-tilt angle can reach+/−65°. The samples can be prepared using coarse grounding to a thickness below 100 microns and with various shapes, either spherical (diameter of 3 mm) or rectangular (1 mm by 3 mm) followed by standard electropolishing. Using a bright-field STEM technique images for tilt-angles ranging from −60° and +54° and can be made, and reconstructed.

Mechanical Properties

Since mechanical properties are strongly correlated to nanoporous high entropy alloy microstructures, it is important to characterize their microstructures before and after mechanical testing. Defects, such as segregation, non-uniform grain sizes, and the presence of non-equilibrium phases, can degrade the mechanical properties during the hot isostatic press process. A better balance of strength and ductility can be reached after thermal treatment. Therefore, application of thermal treatment as needed after the hot isostatic press process, to control the microstructures and to remove some defects is utilized. The detailed microstructural properties are evaluated using the above-mentioned characterization tools before and after thermal processing. These results provide optimized processing conditions for nanoporous high entropy alloys with superior mechanical properties.

The mechanical properties of nanoporous high entropy alloy samples are evaluated using nanoindentation and small-scale test techniques. Prior to dealloying and indentation testing, sample surfaces are carefully polished using a broad-beam ion mill (cross-section polisher from JEOL) in order to prepare smooth, flat surfaces that are free of mechanical sub-surface damage.

In an aspect, automated nanoindentation of nanoporous high entropy alloys is performed to generate statistically significant datasets and allow the determination of reliable mechanical property values, such as modulus and hardness. Nanoindentation is a compressive test however, strong correlation has been shown in nanoporous-Au between hardness and tensile testing of sub-millimeter bulk specimens [Bri¹⁵].

In an aspect, a microspecimen technique provides valuable mechanical test data for understanding materials behavior under various loads. The microspecimen system consists of a dogbone-shaped microspecimen and a load cell of 50 N sample grips (tension and compression modes). Strain is measured using a microscope coupled with a digital camera. Typical sample dimensions are overall length 5 mm, gage length on the order of 1-2 mm, and cross-sections that can range from 20×20 μm² up to 400×100 μm². The small size of samples can allow homogeneity of composition and structure within the studied section. The test system allows strain rates from 10⁻⁶-10⁻¹ s⁻¹. The strain is measured with a 2D full-field with a camera having the following characteristics: acquisition rates of 25 fps at 6.6 Mpixels, to roughly 200 fps at VGA resolution. Digital image correlation is used to understand the elastic and plastic behavior and the crack propagation for fracture toughness measurements.

Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described aspects are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described aspects are combinable and interchangeable with one another.

Many modifications and other aspects disclosed herein will come to mind to one skilled in the art to which the disclosed compositions and methods pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosures are not to be limited to the specific aspects disclosed and that modifications and other aspects are intended to be included within the scope of the appended claims. The skilled artisan will recognize many variants and adaptations of the aspects described herein. These variants and adaptations are intended to be included in the teachings of this disclosure and to be encompassed by the claims herein.

Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual aspects described and illustrated herein has discrete components and features which can be readily separated from or combined with the features of any of the other several aspects without departing from the scope or spirit of the present disclosure.

Any recited method can be carried out in the order of events recited or in any other order that is logically possible. That is, unless otherwise expressly stated, it is in no way intended that any method or aspect set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not specifically state in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including matters of logic with respect to arrangement of steps or operational flow, plain meaning derived from grammatical organization or punctuation, or the number or type of aspects described in the specification.

All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided herein can be different from the actual publication dates, which can require independent confirmation.

While aspects of the present disclosure can be described and claimed in a particular statutory class, such as the system statutory class, this is for convenience only and one of skill in the art will understand that each aspect of the present disclosure can be described and claimed in any statutory class.

It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the disclosed compositions and methods belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

A. DEFINITIONS

As used herein, “comprising” is to be interpreted as specifying the presence of the stated features, integers, steps, or components as referred to, but does not preclude the presence or addition of one or more features, integers, steps, or components, or groups thereof. Moreover, each of the terms “by”, “comprising,” “comprises”, “comprised of,” “including,” “includes,” “included,” “involving,” “involves,” “involved,” and “such as” are used in their open, non-limiting sense and may be used interchangeably. Further, the term “comprising” is intended to include examples and aspects encompassed by the terms “consisting essentially of” and “consisting of.” Similarly, the term “consisting essentially of” is intended to include examples encompassed by the term “consisting of.

It should be noted that ratios, concentrations, amounts, and other numerical data can be expressed herein in a range format. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms a further aspect. For example, if the value “about 10” is disclosed, then “10” is also disclosed.

When a range is expressed, a further aspect includes from the one particular value and/or to the other particular value. For example, where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure, e.g. the phrase “x to y” includes the range from ‘x’ to ‘y’ as well as the range greater than ‘x’ and less than ‘y’. The range can also be expressed as an upper limit, e.g. ‘about x, y, z, or less’ and should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘less than x’, less than y’, and ‘less than z’. Likewise, the phrase ‘about x, y, z, or greater’ should be interpreted to include the specific ranges of ‘about x’, ‘about y’, and ‘about z’ as well as the ranges of ‘greater than x’, greater than y’, and ‘greater than z’. In addition, the phrase “about ‘x’ to ‘y’”, where ‘x’ and ‘y’ are numerical values, includes “about ‘x’ to about ‘y’”.

It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a numerical range of “about 0.1% to 5%” should be interpreted to include not only the explicitly recited values of about 0.1% to about 5%, but also include individual values (e.g., about 1%, about 2%, about 3%, and about 4%) and the sub-ranges (e.g., about 0.5% to about 1.1%; about 5% to about 2.4%; about 0.5% to about 3.2%, and about 0.5% to about 4.4%, and other possible sub-ranges) within the indicated range.

As used herein, the terms “about,” “approximate,” “at or about,” and “substantially” mean that the amount or value in question can be the exact value or a value that provides equivalent results or effects as recited in the claims or taught herein. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art such that equivalent results or effects are obtained. In some circumstances, the value that provides equivalent results or effects cannot be reasonably determined. In such cases, it is generally understood, as used herein, that “about” and “at or about” mean the nominal value indicated ±10% variation unless otherwise indicated or inferred. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about,” “approximate,” or “at or about” whether or not expressly stated to be such. It is understood that where “about,” “approximate,” or “at or about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

Unless otherwise specified, temperatures referred to herein are based on atmospheric pressure (i.e. one atmosphere).

B. ASPECTS

The following listing of exemplary aspects supports and is supported by the disclosure provided herein.

Aspect 1. A nanoporous alloy prepared by a process comprising:

• • (i) admixing at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu), with a sacrificial element selected from the group consisting of lead (Pb), tin (Sn), magnesium (Mg), and bismuth (Bi);
  • wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;
  • wherein each of the at least three different elements independently has an average particle size of from 10 nm to 500 nm as measured by dynamic light scattering;
  • (ii) heating the resulting admixture to an elevated temperature of from about 800° C. to about 2500° C. at atmospheric pressure for a period of time to provide a precursor alloy; and
  • (iii) dealloying the precursor alloy to remove the sacrificial element to provide a nanoporous alloy wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a bulk alloy comprising the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 2. A nanoporous alloy prepared by a process comprising:

• • (i) admixing at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu);
  • wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;
  • wherein each of the at least three different elements independently has an average particle size of from 10 nm to 500 nm as measured by dynamic light scattering;
  • (ii) heating the resulting admixture to an elevated temperature of from about 800° C. to about 2500° C. at atmospheric pressure to provide a precursor alloy;
  • (iii) admixing the precursor alloy at atmospheric pressure and temperature with a sacrificial element in a liquid state, wherein the sacrificial element is selected from the group consisting of lead (Pb), tin (Sn), magnesium (Mg), and bismuth (Bi), to produce a second admixture; and
  • (iv) dealloying the second admixture to remove the sacrificial element to provide a nanoporous alloy wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a bulk alloy comprising the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure Aspect 3. The nanoporous alloy of aspect 1 wherein the dealloying comprises mixing the precursor alloy with an acidic liquid composition to remove substantially all the sacrificial element.

Aspect 4. The nanoporous alloy of aspect 1 wherein the dealloying comprises heating the precursor alloy to the sublimation temperature of the sacrificial element at atmospheric pressure or below atmospheric pressure.

Aspect 5. The nanoporous alloy of aspect 2 wherein the dealloying comprises mixing the second admixture with an acidic liquid composition to remove substantially all the sacrificial element.

Aspect 6. The nanoporous alloy of aspect 2 wherein the dealloying comprises heating the second admixture to the sublimation temperature of the sacrificial element at atmospheric pressure or below atmospheric pressure to remove substantially all the sacrificial element.

Aspect 7. The nanoporous alloy of any one of the foregoing aspects, wherein a specific modulus of the nanoporous alloy is from about 10⁻³ to about 10⁻² GPa/(kg/m³).

Aspect 8. The nanoporous alloy of any one of the foregoing aspects, wherein a specific strength of the alloy is from about 10⁻¹ to about 10⁰ MPa/(kg/m³).

Aspect 9. The nanoporous alloy of any one of the foregoing aspects, which comprises a face-centered cubic phase.

Aspect 10. The nanoporous alloy of any one of the foregoing aspects, which comprises a body-centered cubic phase.

Aspect 11. The nanoporous alloy of any one of the foregoing aspects, which comprises multiple phases.

Aspect 12. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 13. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 30% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 14. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 40% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 15. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 50% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 16. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 60% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 17. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 70% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 18. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 70% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 19. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 30% to 70% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 20. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 40% to 70% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 21. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 50% to 70% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 22. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 60% to 70% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 23. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 60% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 24. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 30% to 60% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 25. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 40% to 60% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 26. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 50% to 60% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 27. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 50% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 28. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 30% to 50% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 29. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 40% to 50% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 30. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 40% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 31. The nanoporous alloy of any one of the foregoing aspects, which has a relative density of from 20% to 30% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

Aspect 32. The nanoporous alloy of any one of the foregoing aspects, wherein one of the at least three elements are selected from the group consisting of aluminum, vanadium, and halfnium.

Aspect 33. The nanoporous alloy of any one of the foregoing aspects, wherein one of the at least three elements are selected from the group consisting of chromium, manganese, and niobium.

Aspect 34. The nanoporous alloy of any one of the foregoing aspects, wherein one of the at least three elements are selected from the group consisting of iron, molybdenum, tantalum, and copper.

Aspect 35. The nanoporous alloy of any one of the foregoing aspects, wherein one of the at least three elements are selected from the group consisting of cobalt, copper, tantalum, titanium, and nickel.

Aspect 36. The nanoporous alloy of any one of the foregoing aspects, wherein one of the at least three elements are selected from the group consisting of nickel, tungsten, zirconium, and zinc.

Aspect 37. The nanoporous alloy of any one of the foregoing aspects, which has the following formula:

• • CrMnFeCoNi,
  • Body-centered cubic VNbMoTaW,
  • Body-centered cubic HfNbTaTiZr,
  • Face-centered cubic AlCoNiCuZn; or
  • AlxCrFeCoNiCu, wherein x is less than 1.

38. A continuous nanoporous alloy comprising at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu);

• • wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;
  • wherein the continuous nanoporous alloy comprises an average ligament size of about 3 nm to about 100 nm when measured by SEM, TEM, and/or small angle neutron scattering;
  • wherein the continuous nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a reference specific strength of a bulk alloy comprising the same at least three different elements in the same molar equivalents except without the continuous nanoporous structure.

From the foregoing, it will be seen that aspects herein are well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure.

While specific elements and steps are discussed in connection to one another, it is understood that any element and/or steps provided herein is contemplated as being combinable with any other elements and/or steps regardless of explicit provision of the same while still being within the scope provided herein.

It will be understood that certain features and subcombinations are of utility and can be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

Since many possible aspects can be made without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings and detailed description is to be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting. The skilled artisan will recognize many variants and adaptations of the aspects described herein. These variants and adaptations are intended to be included in the teachings of this disclosure and to be encompassed by the claims herein.

References are provided in Appendix 1.

The Reference [Wor²²] is incorporated herein and relied upon.

Claims

1. A nanoporous alloy prepared by a process comprising: (i) admixing at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu), with a sacrificial element selected from the group consisting of lead (Pb), tin (Sn), magnesium (Mg), and bismuth (Bi);wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;wherein each of the at least three different elements independently has an average particle size of from 10 nm to 500 nm as measured by dynamic light scattering;(ii) heating the resulting admixture to an elevated temperature of from about 800° C. to about 2500° C. at atmospheric pressure for a period of time to provide a precursor alloy; and(iii) dealloying the precursor alloy to remove the sacrificial element to provide a nanoporous alloy wherein the nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a bulk alloy comprising the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

2. The nanoporous alloy of claim 1 wherein the dealloying comprises mixing the precursor alloy with an acidic liquid composition to remove substantially all the sacrificial element.

3. The nanoporous alloy of claim 1 wherein the dealloying comprises heating the precursor alloy to the sublimation temperature of the sacrificial element at atmospheric pressure or below atmospheric pressure.

4. The nanoporous alloy of claim 1, wherein a specific modulus of the nanoporous alloy is from about 10−3 to about 10−2 GPa/(kg/m3).

5. The nanoporous alloy of claim 1, wherein a specific strength of the alloy is from about 10−1 to about 100 MPa/(kg/m3).

6. The nanoporous alloy of claim 1, which comprises a face-centered cubic phase.

7. The nanoporous alloy of claim 1, which comprises a body-centered cubic phase.

8. The nanoporous alloy of claim 1, which comprises multiple phases.

9. The nanoporous alloy of claim 1, which has a relative density of from 20% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

10. The nanoporous alloy of claim 1, which has a relative density of from 30% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

11. The nanoporous alloy of claim 1, which has a relative density of from 40% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

12. The nanoporous alloy of claim 1, which has a relative density of from 50% to 80% of a bulk alloy of the same at least three different elements and having the same molar equivalents as after the dealloying, except without the nanoporous structure.

13. The nanoporous alloy of claim 1, wherein one of the at least three elements are selected from the group consisting of aluminum, vanadium, and halfnium.

14. The nanoporous alloy of claim 1, wherein one of the at least three elements are selected from the group consisting of chromium, manganese, and niobium.

15. The nanoporous alloy of claim 1, wherein one of the at least three elements are selected from the group consisting of iron, molybdenum, tantalum, and copper.

16. The nanoporous alloy of claim 1, wherein one of the at least three elements are selected from the group consisting of cobalt, copper, tantalum, titanium, and nickel.

17. The nanoporous alloy of claim 1, wherein one of the at least three elements are selected from the group consisting of nickel, tungsten, zirconium, and zinc.

18. The nanoporous alloy of claim 1, which has the following formula: face-centered cubic (fcc) or body-centered cubic (bcc) Al0.1CoCrFeNi,fcc or bcc NbMoTaW,CrMnFeCoNi,bcc VNbMoTaW,bcc HfNbTaTiZr,fcc AlCoNiCuZn; orAlxCrFeCoNiCu, wherein x is less than 1.

19. A continuous nanoporous alloy comprising at least three different elements, wherein each of the at least three different elements are selected from the group consisting of aluminum (Al), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), vanadium (V), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), titanium (Ti), zirconium (Zr), zinc (Zn), halfnium (Hf), copper (Cu); wherein each of the at least three different elements is present in a molar equivalent from about 0.0 to about 1.0;wherein the continuous nanoporous alloy comprises an average ligament size of about 3 nm to about 100 nm when measured by SEM, TEM, and/or small angle neutron scattering;wherein the continuous nanoporous alloy has a specific strength that is from about 2× to about 10× greater than a reference specific strength of a bulk alloy comprising the same at least three different elements in the same molar equivalents except without the continuous nanoporous structure.