NICKEL-IRON-ALUMINUM-CHROMIUM BASED ALLOYS, AND PRODUCTS MADE THEREFROM

Abstract

The present disclosure relates to new nickel-iron-aluminum-chromium based alloys. Generally, the new alloys contain 20-40 at. % Ni, 15-40 at. % Fe, 5-20 at % Al, and 5-26 at. % Cr, the balance being optional incidental elements and unavoidable impurities. Generally, methods for producing the new alloys include one or more of heating a mixture above its liquidus temperature, then cooling the mixture below its solidus temperature, optionally hot and/or cold working the solid material into a final product form, then heating and quenching the solid material, and precipitation hardening the solid material.

Claims

1. A method comprising: (a) heating a mixture above its liquidus temperature, wherein the mixture comprises: (i) 20-40 at. % Ni; (ii) 15-40 at. % Fe; (iii) 5-20 at % Al; and (iv) 5-26 at. % Cr; (b) cooling the mixture below its solidus temperature, thereby forming a solid material having a mixed fcc+bcc crystalline structure, wherein the mixture includes a sufficient amount of the Ni, the Fe, the Al and the Cr to realize the mixed fcc+bcc crystalline structure; (c) optionally hot and/or cold working the solid material into a final product form; (d) heating the solid material, thereby dissolving at least some second phase particles within the solid material; (e) quenching the solid material; and (f) precipitation hardening the solid material, thereby forming precipitates within the mixed fcc+bcc crystalline structure of the solid material.

2. The method of claim 1, wherein the mixture comprises 60-77 at. % Ni+Fe.

3. The method of claim 2, wherein the mixture comprises 23-40 at. % Al+Cr.

4. The method of claim 3, wherein the mixture includes 27.5-40 at. % Ni.

5. The method of claim 4, wherein the mixture includes 25-40 at. % Fe.

6. The method of claim 5, wherein the mixture includes at least 12 at. % Cr.

7. The method of claim 6, wherein the mixture includes not greater than 16 at. % Al.

8. The method of claim 1, wherein the balance of the solid material is optional incidental elements and unavoidable impurities, wherein the optional incidental elements comprise: up to 15 at. %, in total, of one or more of cobalt (Co), copper (Cu), molybdenum (Mo), manganese (Mn), and tungsten (W); up to 10 at. %, in total, of one or more of niobium (Nb), tantalum (Ta), and titanium (Ti); up to 10 at. % carbon (C); up to 5 at. % of silicon (Si); up to 5 at. %, in total, of one or more of vanadium (V) and hafnium (Hf); up to 2 at. %, in total, of one or more of boron (B) and zirconium (Zr); up to 1 at. %, in total, of magnesium (Mg), calcium (Ca), cerium (Ce) and lanthanum (La); up to 1 at. % of nitrogen (N); and up to 10 vol. % of at least one ceramic material.

9. The method of claim 8, wherein the mixture includes at least 0.5 at. % Ti.

10. The method of claim 9, wherein a combined amount of Al plus Ti in the mixture is not greater than 20 at. %.

11. The method of claim 1, wherein the solid material comprises an alloy matrix and wherein the alloy matrix comprises at least 3.0 vol. % of fcc crystalline structures.

12. The method of claim 11, wherein the cooling the mixture below its solidus temperature step comprises first forming fcc crystalline structures from the mixture and then forming bcc crystalline structures.

13. The method of claim 12, wherein the solid material comprises dendritic fcc crystalline structures.

14. The method of claim 1, wherein the heating step (a) comprises selectively heating a portion of a powder comprising the mixture via a laser, thereby forming a molten pool having at least Ni, Fe, Al, and Cr therein; and wherein the cooling step (b) comprises cooling the molten pool at a cooling rate of at least 1000 C. per second.

15. The method of claim 1, wherein step (c) is completed and the method includes hot and/or cold working the solid material into the final product form; wherein the heating step (d) comprises heating the final product form, thereby dissolving at least some second phase particles within the final product form; wherein the quenching step (e) comprises quenching the final product form; and wherein the precipitating hardening step (f) comprises precipitation hardening the final product form, thereby forming precipitates within the mixed fcc+bcc crystalline structure of the final product form.

16. The method of claim 15, wherein the forming precipitates comprises forming at least 0.5 vol. % of the precipitates within the mixed fcc+bcc crystalline structure of the final product form.

17. The method of claim 16, wherein the precipitates comprise at least one of L1.sub.2, L2.sub.1, B2, Laves, delta, and D0.sub.22.

18. The method of claim 16, wherein the forming precipitates comprise forming at least one of L1.sub.2, L2.sub.1, B2, delta, and D0.sub.22, and wherein the final product form is essentially free of Laves precipitates.

19. The method of claim 1, wherein the mixture comprises 20-40 at. % Ni, 20-40 at. % Fe, 5-16 at % Al, 8-26 at. % Cr, and 0.5-10 at. % Ti.

20. The method of claim 1, wherein the mixture comprises 20-40 at. % Ni, 20-35 at. % Fe, 6-14 at % Al, and 18-22 at. % Cr, and 1.0-7.0 at. % Ti.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG. 1 is a schematic illustration of bcc, fcc, and hcp unit cells.

[0081] FIG. 2 is a schematic illustration of a B2 unit cell, wherein X and Y are different elements within the unit cell.

[0082] FIG. 3 is a flow chart of one embodiment of a method to produce a new material.

[0083] FIG. 4 is a flow chart of one embodiment of a method to obtain a wrought product.

[0084] FIG. 5 is an SEM micrograph of Alloy 2 from Example 1 showing a crack.

[0085] FIG. 6 is an SEM micrograph at 500 magnification of Sample A-14 from Example 2; the microstructure shows a predominantly bcc crystalline structure.

[0086] FIG. 7 is an SEM micrograph at 10,000 magnification of Sample A-15 from Example 2; the microstructure shows a mixed fcc+bcc crystalline structure.

[0087] FIG. 8 is an SEM micrograph at 10,000 magnification of Sample A-16 from Example 2; the microstructure shows fcc crystalline structures within the bcc crystalline structures.

[0088] FIG. 9a is an SEM micrograph at 500 magnification of Sample A-17 from Example 2; the microstructure shows a predominantly bcc crystalline structure.

[0089] FIG. 9b is a portion of FIG. 9a at 8,000 magnification; fcc crystalline structures are located along the boundaries of the bcc crystalline structures.

[0090] FIG. 10 is an SEM micrograph at 5,000 magnification of Sample A-18 from Example 2; the microstructure shows fcc crystalline structures located along the boundaries of the bcc crystalline structures, and fcc crystalline structures within the bcc crystalline structures, and generally equiaxed crystalline structures (grains).

[0091] FIG. 11 is an SEM micrograph at 5,000 magnification of Sample A-19 from Example 2; the microstructure shows fcc crystalline structures located along the boundaries of the bcc crystalline structures, and fcc crystalline structures within the bcc crystalline structures, and generally equiaxed crystalline structures (grains).

[0092] FIG. 12a is an SEM micrograph at 500 magnification of Sample A-20 from Example 2; the microstructure shows a mixed fcc+bcc crystalline structure.

[0093] FIG. 12b is a portion of FIG. 12a at 10,000 magnification.

[0094] FIG. 13a is an SEM micrograph at 500 magnification of Sample A-21 from Example 2; the microstructure shows a mixed fcc+bcc crystalline structure.

[0095] FIG. 13b is a portion of FIG. 13a at 10,000 magnification.

[0096] FIG. 14 illustrates the matrix vol. % of fcc crystalline structures versus the solidification rate for as-solidified Alloy A from Example 2.

[0097] FIG. 15 illustrates the matrix vol. % of fcc crystalline structures versus the solidification rate for as-solidified Alloy 6 from Example 1.

DETAILED DESCRIPTION

Examples

Example 1

[0098] Seventeen experimental alloys were produced having the nominal compositions given in Table 1A, below. Furthermore, densities of the alloys measured by Archimedes method are given in Table 1A, below.

TABLE-US-00001 TABLE 1A Nominal Compositions of Example 1 Alloys (in at. %) Alloy Density No. Ni Fe Cr Al Ti Nb B C Hf Zr (g/cm.sup.3) 1 Bal. 32 20 14 1 7.3 2 Bal. 32 20 13 1 1 7.4 3 Bal. 30 20 7.5 7.5 7.5 4 Bal. 32 20 9 1 3 7.6 5 Bal. 28 18 12 3 1 7.6* 6 Bal. 28 18 12 3 1 0.05 0.2 7.6* 7 Bal. 30 20 7.5 7.5 0.05 0.21 7.4 8 Bal. 30 20 7.5 7.5 0.05 0.21 0.15 0.06 7.4* 9 Bal. 30 20 14 1 7.3 10 Bal. 30 20 11 4 7.4 11 Bal. 30 20 6 6 7.6 12 Bal. 30 20 9 9 7.6 13 Bal. 32 20 13 1 1 0.05 0.21 0.15 0.06 7.3 14 Bal. 32.7 20 14 7.4* 15 Bal. 32.7 19.9 14 0.9 7.3* 16 Bal. 31.8 19.3 13.6 4.2 7.2* 17 Bal. 29.8 18.1 12.7 11.8 6.8* *Estimated based on alloy of similar composition. **Bal. = the balance of the alloy was nickel.

[0099] Some of the experimental alloys were cast as rectangular ingots (0.5 inch0.5 inch3 inches) for tensile property evaluation. The ingots were cut into cylindrical specimens of 1.5 inches in length and 0.2 inch in diameter using electrical discharge machining. The cylindrical specimens were then lathed into standard testing blanks, each having a larger cylindrical shoulder at each end and a smaller cylindrical gage section in between the shoulders. Some of the testing blanks were heat treated prior to tensile testing as described in Tables 1B and 1C, below.

Room Temperature Tensile Properties

[0100] The room temperature tensile properties (tensile yield strength (TYS), ultimate tensile strength (UTS), elongation, and specific yield strength) of some experimental alloys were evaluated in the as-cast condition, while others were evaluated after thermal processing. The evaluation was performed in the longitudinal direction and in accordance with ASTM E8 (rev. #8M-16A). Results from the evaluation are given in Table 1B, below.

TABLE-US-00002 TABLE 1B Room Temperature Tensile Testing Results Specific Yield Alloy Thermal TYS UTS Elongation Strength No. Treatment (if any) (ksi) (ksi) (%) (ksi*in.sup.3/lbs) 1 Type 1 152 207 13 576 9 Type 2 108 179 13.3 405 10 Type 2 143 188 4.4 533 3 Type 2 173 194 2.2 640 11 Type 2 164 178 2.2 607 1 N/A - As-cast 113 186 20 428 3 N/A - As-cast 128 151 2.2 472 9 N/A - As-cast 92 171 18.9 342 10 N/A - As-cast 97 170 16.7 362 11 N/A - As-cast 120 167 13.3 441

Elevated Temperature Tensile Properties

[0101] The elevated temperature (650 C.) tensile properties of some experimental alloys were evaluated after thermal treatment. The evaluation was performed in the longitudinal direction, and in accordance with ASTM E21-09. Results from the evaluation are given in Table 1C, below.

TABLE-US-00003 TABLE 1C Elevated Temperature (650 C.) Tensile Testing Results Specific Yield Alloy Thermal TYS UTS Elongation Strength No. Treatment (ksi) (ksi) (%) (ksi*in.sup.3/lbs) 2 Type 1 106 138 36 396 3 Type 2 140 169 20 517 4 Type 1 122 161 25 444 5 Type 2 130 164 25 473 9 Type 2 69 99 31 260 10 Type 2 105 137 30 393

Solidification Rate Evaluations

[0102] The experimental alloys were solidified by two methods that realize solidification rates on the order of 1,000,000 C./s and 10,000-100,000 C./s. Following solidification, the tendency for the material to crack at the employed solidification rate was evaluated in the as-solidified condition. The tendency for the material to crack was evaluated by (1) visual inspection (e.g., with the human eye) and/or (2) micrograph inspection. In this regard, the experimental alloys were evaluated on a qualitative pass/fail rating, where a pass rating indicates the as-solidified material was free of cracks and a fail rating indicates the material contained at least one crack. The as-solidified materials were first analyzed by visual inspection. If it was apparent from visual inspection that the solidified material contained cracks, the alloy was given a rating of fail. If the material appeared to have no cracks by visual inspection, appropriate micrographs were taken and analyzed to make the determination. Results from the solidification evaluations are given in Table 1D, below. An example micrograph of Alloy 2, having been solidified at approximately at 1,000,000 C./s is given in FIG. 5. As illustrated in FIG. 5, a crack near the surface of the material can be seen at 1,000 magnification. An example micrograph of Alloy 1 having been solidified at approximately 10,000 C./s is given in FIG. 10. As illustrated in FIG. 10, the material is free of cracks.

TABLE-US-00004 TABLE 1D Solidification Experiment Cracking Evaluation Results Alloy Solidification No. 1,000,000 C./s 10,000-100,000 C./s Pathway 1 Fail Pass near-eutectic* 2 Fail Fail near eutectic* 3 Pass Pass fcc-first 4 Pass Pass fcc-first 5 Pass Pass fcc-first 6 Pass Pass fcc-first 7 Pass Pass fcc-first 8 Pass Pass fcc-first 9 Pass Pass fcc-first 10 Pass Pass fcc-first 11 Pass Pass fcc-first 12 Pass Pass fcc-first 13 Fail Fail near eutectic* 14 N/A N/A N/A 15 Pass Pass fcc-first 16 Pass Pass bcc-first 17 Fail Fail bcc-first *Near-eutectic solidification pathway reflects a solidification pathway where fcc and bcc generally form concomitantly (i.e., neither an fcc-first or bcc-first solidification pathway).

Example 2

Tensile Properties Evaluation

[0103] Three additional experimental alloys were cast as ingots (0.5 inch0.5 inch3 inch). The nominal compositions of the three additional experimental alloys are given in Table 2A, below. Alloy A has the same nominal composition as Alloy 1 of Example 1, above. Alloy B is a prior art alloy from Dong, Y., Gao, X., Lu, Y., Wang, I., & Li, T. (2016). A multi-component AlCrFe2Ni2 alloy with excellent mechanical properties. Materials Letters, 169, 62-64., and Alloy C is a prior art alloy from Dong, Y., Lu, Y., Kong, J., Zhang, J., & Li, T. (2013). Microstructure and mechanical properties of multi-component AlCrFeNiMox high-entropy alloys. Journal of Alloys and Compounds, 573, 96-101.

TABLE-US-00005 TABLE 2A Nominal Compositions of Experimental Alloys A, B, and C Alloy No. Ni Fe Cr Al Ti A 33 32 20 14 1 (Inv.) B 33.3 33.3 16.7 16.7 Trace (Prior Art) C 25 25 25 25 Trace (Prior Art)

[0104] Following casting, some ingots of Alloy A and B were cut in the longitudinal direction into rectangular samples (0.25 inch0.5 inch3 inches) in preparation for rolling. The samples were heated to 900 C. and hot rolled, in six passes, to a net relative reduction of approximately 55%. The wrought samples were examined for edge cracking. Alloy A appeared to be free of cracks, while Alloy B exhibited severe edge cracking. Alloy A was therefore in a condition for further testing, described below.

Wrought Samples

[0105] Four specimens (A-1 through A-4) from the Alloy A ingots were thermally treated, after which, room temperature tensile properties were measured in the longitudinal direction and in accordance with ASTM E8 (rev. #8M-16A). The results from the evaluation are given in Table 2B, below.

TABLE-US-00006 TABLE 2B Wrought Room Temperature Tensile Properties of Alloy A Sample Thermal TYS UTS Elong. No. Treatment (ksi) (ksi) (%) A-1 Practice #1 124 169 17 A-2 Practice #2 161 196 10 A-3 Practice #3 142 182 8 A-4 Practice #4 108 158 21

Non-Wrought Samples

[0106] Four specimens (A-5 through A-8) from the Alloy A ingots and four specimens (C-1 through C-4) from the Alloy C ingots were thermally treated, after which room temperature tensile properties of heat treated samples were measured in accordance with ASTM E8 (rev. #8M-16A). Samples of Alloy C were thermally treated in an argon atmosphere to prevent oxidation. As illustrated in Table 2C, the samples of Alloy C failed before yielding. Thus, only the ultimate tensile strength was measured for the Alloy C samples, and no further samples were evaluated due to the poor ductility.

TABLE-US-00007 TABLE 2C As-Cast Room Temperature Tensile Properties of Alloy A and C Sample Thermal TYS UTS Elong. No. Treatment (ksi) (ksi) (%) A-5 Condition #1 69 153 28 A-6 Condition #2 96 154 12 A-7 Condition #3 116 179 11 A-8 Condition #4 156 212 14 C-1 Condition #5 116 0.0 C-2 Condition #5 100 0.0 C-3 Condition #5 85 0.0 C-4 Condition #5 103 0.0

[0107] Four additional specimens (A-8 through A-13) from the Alloy A ingots were prepared for tensile testing in the as-cast condition (i.e., without thermal treatment). Sample A-9 was evaluated at room temperature in the longitudinal direction and in accordance with ASTM E8 (rev. #8M-16A). Samples A-10 through A-13 were evaluated in the longitudinal direction at 500 C., 600 C., 650 C., and 700 C., and in accordance with ASTM E21-09. Results from the evaluations are given in Table 2D, below.

TABLE-US-00008 TABLE 2D Tensile Testing Results for As-Cast Alloy A at Various Temperatures Sample Temperature TYS UTS Elong. No. ( C.) (ksi) (ksi) (%) A-9 25 113 176 13 A-10 500 97 144 39 A-11 600 90 116 47 A-12 650 77 105 26 A-13 700 58 81 28

Solidification Rate Evaluations

[0108] As noted above, Alloy A was selected for a separate set of solidification rate evaluations. Samples of Alloy A were solidified at rates varying from about 10 C./s to about 1,000,000 C./s. Following solidification, and in some cases post-solidification thermal treatment, the samples were microstructurally characterized. Furthermore, hardness, room temperature tensile properties, and elevated temperature tensile properties (e.g., 450 C. and 650 C.) of the samples were evaluated. The samples conditions (e.g., as-solidified; thermally treated) are given in Table 2E, below.

Microstructural Characterization

[0109] Alloy A was subjected to solidification rates varying from about 10 C./s to about 1,000,000 C./s. Following solidification, and in some cases following post-solidification thermal treatment, appropriate micrographs were taken of the solidified materials. The solidification rate and conditions (e.g., thermal history or as-solidified) are given in Table 2E, below. Additionally, figure numbers of the micrographs are illustrated in FIGS. 6-13b, are given in Table 2E.

TABLE-US-00009 TABLE 2E Solidification Evaluation Sample Approximate Corresponding No. Solidification Rate Condition FIG(S). A-14 1,000,000 C./s As-solidified FIG. 6 A-15 1,000,000 C./s Solidified and then FIG. 7 thermally treated A-16 1,000,000 C./s Solidified and then FIG. 8 thermally treated A-17 10,000 C./s As-solidified FIGS. 9a to 1,000,000 C./s and 9b A-18 10,000 C./s As-solidified FIG. 10 A-19 1,000 C./s As-solidified FIG. 11 A-20 100 C./s Solidified and then FIGS. 12a thermally treated and 12b A-21 10 C./s-100 C./s As-solidified FIGS. 13a and 13b

[0110] The microstructures shown in FIGS. 6-13b were characterized using Electron Backscatter Diffraction (EBSD) to determine the volumetric percentage of matrix fcc and matrix bcc crystalline structures (i.e., phases other than fcc/bcc were not measured or characterized). Elemental compositions within the fcc and bcc crystalline structures were determined using Energy Dispersive X-Ray Spectroscopy (EDS). Results from the evaluations are given in Table 2F, below. The micrographs given in FIGS. 6-13b (listed above in Table 2E) were used for the microstructural characterization.

TABLE-US-00010 TABLE 2F Microstructural Analysis of fcc and bcc Crystalline Structures Elemental Composition Sample Matrix Vol. within Phase (at. %) No. Phase % of phase Al Cr Fe Ni Ti A-14 fcc 0 bcc 100 13.1 20.3 35.1 30.3 1.2 A-15 fcc 73 6.5 23.4 37.3 31.9 0.9 bcc 27 19.8 11.3 21.0 46.0 1.9 A-16 fcc 1 9.7 20.1 34.9 34.4 0.9 bcc 99 10.1 20.7 34.2 33.9 1.1 A-17 fcc 0 bcc 100 12.2 19.3 35.4 32.2 0.9 A-18 fcc 9 11.7 18.3 31.2 37.7 1.1 bcc 91 9.8 21.4 34.3 33.4 1.1 A-19 fcc 46 9.9 20.4 34.2 34.4 1.1 bcc 54 9.9 20.4 34.2 34.4 1.1 A-20 fcc Not 7.7 21.37 35.6 34.5 0.9 Measured bcc Not 11.4 21.3 32.1 34.1 1.1 Measured A-21 fcc 56 9.7 22.1 37.5 30.0 0.7 bcc 44 15.3 24.1 32.1 27.7 0.8

[0111] As illustrated in Table 2F, solidification rates on the order of 10,000 to 1,000,000 C./s realized low amounts (e.g., less than 5 vol. %) of the fcc phase in the as-solidified condition. A solidification rate on the order of 10,000 C./s realized a slight increase in the amount of fcc phase in the as-solidified condition at 8.55 vol. %. However, at a solidification rate of approximately 1,000 C., a large increase in the amount of fcc phase was realized in the as-solidified condition. These results are further illustrated in FIG. 14. Alloy A solidifies by a near-eutectic solidification pathway.

[0112] Alloy 6 from Example 1 was also evaluated, the results of which are given in Table 2G and FIG. 15. As illustrated, Alloy 6 realizes a microstructure having fcc as the predominant matrix phase over the solidification range of from 10-1,000,000 C./s. Thus, Alloy 6 realizes an fcc-first solidification pathway.

TABLE-US-00011 TABLE 2G Vol. % of Matrix fcc and bcc versus Solidification Rate for Example 1 Alloy 6 Approximate Solidification Rate Matrix Vol. % fcc 1000000 C./s 99 10,000-100,000 C./s 87 10 C./s 83

Hardness Evaluation

[0113] Specimens A-14 through A-21 were also subjected to hardness testing in accordance with ASTM E92. Results for the evaluations (given in Vickers Pyramid Numbers (HV)) are given in Table 2H, below. Values are an average of multiple specimens and corresponding uncertainties reflect a normally distributed, 95% confidence interval (i.e., 2-sigma).

TABLE-US-00012 TABLE 2H Hardness Evaluation Results Sample No. Hardness A-14 643 42 A-15 286 54 A-16 616 80 A-17 630 40 A-18 544 30 A-19 389 16 A-20 A-21 336 21

Tensile Properties Evaluation

[0114] Room temperature and elevated temperature tensile properties of samples A-18 through A-21 were tested, the results of which are given in Table 21, below. The sample conditions for the tensile property evaluations correspond to the conditions described in Table 2E. Room temperature tensile properties were evaluated in accordance with ASTM E8 (rev. #8M-16A) and elevated temperature tensile properties were evaluated in accordance with ASTM E21-09.

TABLE-US-00013 TABLE 2I Room Temperature and Elevated Temperature Tensile Properties Room Temp. 450 C. 650 C. Sample TYS UTS Elong. TYS UTS Elong. TYS UTS Elong. No. (ksi) (ksi) (%) (ksi) (ksi) (%) (ksi) (ksi) (%) A-18 183 240 3 144 205 49 52 101 67 A-19 142 205 16 A-20 158 218 7 122 165 11 75 114 18 A-21 113 186 20 97 144 39 77 105 26

[0115] While various embodiments of the new technology described herein have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the presently disclosed technology.