MECHANICAL AND CORROSION PROPERTIES FOR VARIOUS HIGH ENTROPY ALLOY COMPOSITIONS

Abstract

A high entropy alloy composition and methods of manufacturing such composition are provided. In one embodiment, the composition includes iron (Fe) in a range of 0-30% by weight, nickel (Ni) in a range of 20-55% by weight, cobalt (Co) in a range of 5-45% by weight, chromium (Cr) in a range of 0-40% by weight, aluminum (Al) in a range of 0-20% by weight, manganese (Mn) in a range of 0-5% by weight, and niobium in a range of 0-10% by weight.

Claims

1. A high entropy alloy, comprising: about 0-30% iron, by weight; about 20-55% nickel, by weight; about 0-60% cobalt, by weight; about 0-20% chromium, by weight; about 0-20% aluminum, by weight; about 0-5% manganese, by weight; and about 0-10% niobium, by weight.

2. The alloy of claim 1, wherein the aluminum has a purity of 99.99%.

3. The alloy of claim 1, wherein the cobalt has a purity of 99.95%.

4. The alloy of claim 1, wherein the chromium has a purity of 99.5%.

5. The alloy of claim 1, wherein the iron has a purity of 99.99%.

6. The alloy of claim 1, wherein the nickel has a purity of 99.98%.

7. The alloy of claim 1, wherein the nickel has a purity of 99.95%.

8. The alloy of claim 1, wherein the niobium has a purity of 99.9%.

9. A high entropy alloy, comprising: about 0-25% iron, by atomic ratio; about 30-60% nickel, by atomic ratio; about 5-45% cobalt, by atomic ratio; about 0-40% chromium, by atomic ratio; about 0-20% aluminum, by atomic ratio; about 0-10% manganese, by atomic ratio; and about 0-10% niobium, by atomic ratio.

10. The alloy of claim 9, wherein the aluminum has a purity of 99.99%.

11. The alloy of claim 9, wherein the cobalt has a purity of 99.95%.

12. The alloy of claim 9, wherein the chromium has a purity of 99.5%.

13. The alloy of claim 9, wherein the iron has a purity of 99.99%.

14. The alloy of claim 9, wherein the nickel has a purity of 99.98%.

15. The alloy of claim 9, wherein the nickel has a purity of 99.95%.

16. The alloy of claim 9, wherein the niobium has a purity of 99.9%.

17. A method for thermomechanical treatment of a high entropy alloy, comprising at least one of: annealing the high entropy alloy at temperatures from 1000 C. to 1200 C. in an inert atmosphere; air cooling the high entropy alloy to room temperature; cold rolling of the high entropy alloy for a range from 40-90% reduction; aging of the high entropy alloy at temperatures ranging from 600 C. to 950 C.; and quenching the high entropy alloy to room temperature.

18. The method of claim 17, wherein the aging is done for 1 hour under mixed gas comprised of 2% hydrogen and 98% argon.

19. The method of claim 17, wherein the annealing takes place in a tube furnace under mixed gas comprised of 2% hydrogen and 98% argon.

20. The method of claim 17, wherein the annealing takes place for up to 2 hours.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0011] Features and advantages of the present disclosure, including a high entropy alloy composition and methods of manufacturing such composition described herein may be better understood by reference to the accompanying drawings in which:

[0012] FIG. 1 is a table including composition ranges of a targeted HEA by weight percentage, according to an embodiment of the present disclosure.

[0013] FIG. 2 is a table including composition ranges of a targeted HEA by atomic ratio, according to an embodiment of the present disclosure.

[0014] FIG. 3 is a table including exact compositions of various HEAs, according to an embodiment of the present disclosure.

[0015] FIG. 4 includes various graphs outlining the stress versus strain of various HEAs known in the prior art.

[0016] FIG. 5 includes a graph of stress versus strain for various embodiments of the present disclosure at different thermomechanical treatments compared with stainless steel 316 and Inconel 718.

[0017] FIG. 6 includes various graphs outlining the stress versus strain of various HEAs known in the prior art that utilize elements different from those in the present disclosure.

[0018] The reader will appreciate the foregoing details, as with others, upon considering the following detailed description of certain non-limiting embodiments of the present disclosure.

DETAILED DESCRIPTION

[0019] The present disclosure is generally related to a high entropy alloy composition and methods of manufacturing such composition.

[0020] The ranges of embodiments for a high entropy alloy compositions by weight percentage are shown in FIG. 1. In these embodiments, iron (Fe) is included in a range of 0-30% by weight, nickel (Ni) is included in a range of 20-55% by weight, cobalt (Co) is included in a range of 5-45% by weight, chromium (Cr) is included in a range of 0-40% by weight, aluminum (Al) is included in a range of 0-20% by weight, manganese (Mn) is included in a range of 0-5% by weight, and niobium is included in a range of 0-10% by weight.

[0021] FIG. 2 illustrates another embodiment of high entropy alloy compositions by atomic percentage. In these embodiments, iron (Fe) is included in a range of 0-25% by atomic ratio, nickel (Ni) is included in a range of 30-60% by atomic ratio, cobalt (Co) is included in a range of 5-45% by atomic ratio, chromium (Cr) is included in a range of 0-40% by atomic ratio, aluminum (Al) is included in a range of 0-20% by atomic ratio, manganese (Mn) is included in a range of 0-10% by atomic ratio, and niobium is included in a range of 0-10% by atomic ratio. Various specific ratios of compositions of HEAs included within the present disclosure are shown in FIG. 3.

[0022] The HEA compositions as shown in FIGS. 1-3 exhibit mechanical and corrosion properties significantly outperforming conventional alloys (e.g., stainless steel, nickel super alloys, titanium alloys) and exceeding the properties of previously reported HEAs. Thus far, almost all existing research on the mechanical behavior of HEAs composed of nickel, iron, aluminum, chromium, and cobalt elements have either high tensile strength and relatively low ductility or high ductility and relatively low tensile strength, an example of some of the highest reported trends is shown in FIG. 4.

[0023] In addition, as presented, most reported, previously known HEA compositions have equimolar ratios for most of the elements, and studies focus on altering the amount of one or two elements (ex: AlCoCrFeNi.sub.2.1 have aluminum, cobalt, chromium, and iron in the same ratios, while nickel has higher amount). The present disclosure, however, is based on optimized percentages of every single element (ex: Fe.sub.5Ni.sub.50Co.sub.10Cr.sub.25Al.sub.10), which resulted in producing a combination of high tensile strength and high ductility (up to 70%, which has not been reported yet in these elements), as shown in FIG. 5. FIG. 5 illustrates a tensile stress-strain curve of the various disclosed HEA compositions at different thermomechanical treatments as compared with stainless steel 316 and Inconel 718.

[0024] Moreover, some other studies on HEAs with different elements reported a relatively good combination of tensile strength and ductility, but have utilized costly elements such as molybdenum, zirconium, hafnium, tantalum, and tungsten, however, the reported data, such as that shown in FIG. 6, is lower when compared to the present disclosure.

[0025] In addition to the produced combination of high ductility and tensile strength, the present disclosure has exceptional corrosion resistance properties unknown in the prior art. Even though only a few reports on the corrosion behavior of HEAs are available, most reveal a corrosion rate ranging between 0.31-1000 mpy in 3.5 wt % NaCl solution. The present disclosure, astonishingly, has shown an extremely slow corrosion rate of about 1010-6 mpy (indicating that the material barely corrodes at all), which is thus superior to all previously reported corrosion behaviors.

[0026] The resulting HEAs own a combination of high-yield tensile strength (1000-1800 MPa) and high ductility (up to 70%). Moreover, a corrosion resistance of up to 10-6 mpy was recorded. These extraordinary properties, which have never been observed in any commercial alloy generally, or HEAs specifically, are promising for enhancing fuel efficiency and reducing environmental burdens. Applications for these HEAs include military, aerospace, industry, automobiles, construction, transportation, packaging, and architectural infrastructure.

[0027] To manufacture an HEA, raw elements must be obtained. In one such embodiments, the starting materials may be an aluminum slug having a purity of 99.99%, a cobalt slug having a purity of 99.95%, chromium chips having a purity of 99.5%, iron pieces having a purity of 99.99%, a nickel slug having a purity of 99.98%, nickel wire having a purity of 99.95%, and niobium pieces having a purity of 99.9%. The aluminum slug may be obtained from Alfa Aesar and have dimensions of 3.1753.175 mm. The cobalt slug may be obtained from Beantown Chemical and have dimensions of 3.1753.175 mm. The chromium chips may be obtained from Sigma-Aldrich and be 2 mm thick. The iron pieces may be obtained from Beantown Chemical and have dimensions of 3.2-6.4 mm. The nickel slug may be obtained from Nanoshell and have dimensions of 3.1756.35 mm. The nickel wire may be obtained from Beantown Chemical and have dimensions of 12 mm. The niobium pieces may be obtained from ESPI Metals and have dimensions of 3.2-6.4 mm. It will be appreciated that the amounts, purities, dimensions, and sources of the materials obtained may differ in other embodiments.

[0028] To manufacture the HEA compositions, the high-purity elements are weighted according to the specified compositions under ultra-high purity argon atmosphere (where O.sub.2<0.5 ppm) of an mBRAUN-LABstar glovebox. The elements are then placed inside the copper stage of the arc melting device such as one provided by Edmund Buhler GmbH, MAM1, and arranged according to their melting point. The sample chamber is evacuated and refilled with argon three times in order to ensure an oxygen-free atmosphere. After refilling the chamber with argon (pressure of 0.7 bars), a titanium piece is melted a couple of times to reduce the effect of humidity and possible oxidation. The weighted composition is arc melted and the current was increased to 5 A until all the elements combined together. The casted alloy is then flipped and remelted multiple times to ensure homogeneous mixing. The final ingot is annealed at 1000 C. via a tube furnace (such as GSL-1500X-RTP50) under mixed gas (2% hydrogen, 98% argon), then air cooled.

[0029] Further treatments are then carried out based on the desired strength-ductility-corrosion resistance properties. Post-treatments include cold rolling (from 50%-90% reduction), and aging at different temperatures [e.g., 600, 700, 800, 900, 950, 1000 C.] for 1 hour under mixed gas (2% hydrogen, 98% argon).

[0030] Optimized thermomechanical treatments may also be performed on the high entropy alloy. These thermomechanical treatments are different per composition and may include any of the following: annealing of the HEA at temperatures from 1000 C. to 1200 C. in an inert atmosphere for up to 2 hours; air cooling the HEA to room temperature; cold rolling of the HEA for a range from 40% to 90% reduction; aging of the HEA at temperatures ranging from 600 C. to 950 C. for one hour; and quenching the HEA to room temperature. Some compositions may require a second aging step at 700 C.-800 C. for a range of aging time of 6-8 hours.

[0031] Additionally, the composition of the HEA may be changed by changing the processing conditions (such as temperature of annealing, cooling rate) or post-processing treatments (aging temperatures, rolling temperature, further treatments, precipitation hardening processes, etc.). Altering the techniques used to prepare the HEA may also alter the HEA composition. This may include using ball milling or laser cladding materials. It will be appreciated that the methods for manufacturing and thermomechanical treatments listed in the present disclosure are purely exemplary and other methods for manufacturing and thermomechanical treatments may exist.

[0032] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.