MULTI-PRINCIPAL ELEMENT ALLOY FILLER MATERIALS

Info

Publication number: 20240150873
Type: Application
Filed: Mar 23, 2023
Publication Date: May 9, 2024
Inventors: Zhenzhen YU (Golden, CO), Benjamin T. SCHNEIDERMAN (Golden, CO), Minrui GAO (Golden, CO)
Application Number: 18/188,920

Abstract

An example MPEA filler includes manganese at about 10 atomic percent to about 60 atomic percent, iron at about 0 atomic percent to about 35 atomic percent, cobalt at about 0 atomic percent to about 35 atomic percent, nickel at about 0 atomic percent to about 35 atomic percent, and copper at about 0 atomic percent to about 35 atomic percent.

Description

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Patent Application No. 63/323,368 filed on Mar. 24, 2022, the disclosure of which is incorporated herein, in its entirety, by this reference.

BACKGROUND

Ni-base superalloy components may be damaged during service in high-temperature applications (e.g. gas turbine engines) and braze repair using filler alloys is often the most feasible and cost-effective means of returning them to service. One group of existing filler alloys for the repair of cracked Ni-base superalloys components include a high content of noble metals. However, such filler alloys possess high raw material costs due to the presence of noble metals which prevent wide spread use of such filler alloys. Another group of filler alloys for the repair of cracked Ni-based superalloys include at least one of boron, silicon, or phosphorus as melting-point depressants. However, the filler alloys including at least one of boron, silicon, or phosphorus frequently introduce brittle boride phases, silicide phases, or other undesirable phases to the repaired region that shorten subsequent product lifetime.

SUMMARY

Embodiments are directed to multi-principal element alloy (“MPCA”) filler materials. In an embodiment, a multi-principal element alloy (“MPEA”) filler material is disclosed. The MPEA filler material includes manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material, iron at 0 atomic percent to about 3 atomic percent of the MPEA filler material, cobalt at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, and copper at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material.

In an embodiment, a MPEA filler material is disclosed. The MPEA filler material includes manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material, iron at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, cobalt at greater than 0 atomic percent to about 19 atomic percent of the MPEA filler material, nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, and copper at greater than 0 at. % to about 35 atomic percent of the MPEA filler material.

In an embodiment, a braze joint is disclosed. The braze joint includes at least one substrate at least partially defining a gap. The braze joint also includes a MPEA filler material. In an example, the MPEA filler material includes manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material, iron at 0 atomic percent to about 3 atomic percent of the MPEA filler material, cobalt at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, and copper at greater than 0 at. % to about 35 atomic percent of the MPEA filler material. In an example, the MPEA filler material includes manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material, iron at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, cobalt at greater than 0 atomic percent to about 19 atomic percent of the MPEA filler material, nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material, and copper at greater than 0 at. % to about 35 atomic percent of the MPEA filler material.

In an embodiment, a method of determining materials for a MPEA filler material is disclosed. The method includes using a parameter-based filtration series modelled to screen a plurality of distinct MPEA systems and selecting the MPEA systems which fit one or more desired parametric requirements. The method also includes screening compositions within a particular selected MPEA system and selecting one or more compositions that are predicted to display desirable solidification behavior for brazing. The desirable attributes of the solidification behavior include at least one of a selected melting point or a selected solidification temperature range. The method also includes predicting interactions between the MPEA filler material and a substrate for at least some of the selected compositions through construction of isopleth phase diagrams.

Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the present disclosure, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings.

FIG. 1A is a set of schematic illustrations of the stages in a practical transient liquid phase (TLP) bonding process.

FIG. 1B is a set of schematic illustrations of the stages of the bonding process with the MPEA filler.

FIG. 2 is a flow chart of the method 200, according to an embodiment.

FIG. 3A illustrates curves resulting from the Scheil simulation of the MnFeCoNiCu system compositions.

FIG. 3B is a histogram of the approximate liquid temperatures for 280 of the MnFeCoNiCu system compositions.

FIG. 3C illustrates the output of the Scheil simulation of five of the MnFeCoNiCu system compositions.

FIGS. 4A and 4B illustrate isopleths for Mn₃₅Fe₅Co₂₀Ni₂₀Cu₂₀.

DETAILED DESCRIPTION

Embodiments are directed to multi-principal element alloy (“MPEA”) filler materials. An example MPEA filler includes manganese at about 10 atomic percent to about 60 atomic percent, iron at about 0 atomic percent to about 35 atomic percent, cobalt at about 0 atomic percent to about 35 atomic percent, nickel at about 0 atomic percent to about 35 atomic percent, and copper at about 0 atomic percent to about 35 atomic percent.

The MPEA filler material may be used to form a braze joint in a substrate (e.g., a superalloy). For example, the substrate may at least partially define a gap (e.g., crack). The MPEA filler material may be at least partially disposed in the gap and then heated to a temperature that is above the melting point of the MPEA filler material and below the melting temperature of the substrate. Heating the MPEA filler material may cause the MPEA filler material to be brazed to the substrate and one or more elements of the MPEA filler material may diffuse into the substrate and one or more elements of the substrate may diffuse into the MPEA filler material. Unlike some conventional filler materials, the MPEA filler material may prevent or at least inhibit the formation of brittle phases after the MPEA filter material is brazed to the substrate. For instance, brazing the MPEA filler material to the substrate may not form or may form negligible quantities of brittle silicides and borides.

As previously discussed, the MPEA filler material includes manganese. The manganese may form about 10 atomic percent to about 60 atomic percent of the MPEA filler material, such as about 10 atomic percent to about 15 atomic percent, about 12.5 atomic percent to about 17.5 atomic percent, about 15 atomic percent to about 20 atomic percent, about 17.5 atomic percent to about 22.5 atomic percent, about 20 atomic percent to about 25 atomic percent, about 22.5 atomic percent to about 27.5 atomic percent, about 25 atomic percent to about 30 atomic percent, about 27.5 atomic percent to about 32.5 atomic percent, about 30 atomic percent to about 35 atomic percent, about 32.5 atomic percent to about 37.5 atomic percent, about 35 atomic percent to about 40 atomic percent, about 37.5 atomic percent to about 42.5 atomic percent, about 40 atomic percent to about 45 atomic percent, about 42.5 atomic percent to about 47.5 atomic percent, about 45 atomic percent to about 50 atomic percent, about 47.5 atomic percent to about 52.5 atomic percent, about 50 atomic percent to about 55 atomic percent, about 52.5 atomic percent to about 57.5 atomic percent, or about 55 atomic percent to about 60 atomic percent. The atomic percent of manganese in the MPEA filler material may be selected based on a number of factors. In an example, the atomic percent of manganese in the MPEA filler material may be selected based on the desired melting temperature (i.e., at least one of the liquidus or solidus temperature) of the MPEA filler material since, generally, increasing the atomic percent of manganese in the MPEA filler material decreases the melting temperature of the MPEA filler material and vice versa. The desired melting temperature is generally selected to be less than the melting temperature of the substrate to which the MPEA filler material is configured to be bonded thereby allowing the MPEA filler material to be brazed to the substrate without melting the substrate. It is noted that, as discussed in more detail below, iron, cobalt, and copper also affect the melting temperature of the MPEA filler material and, as such, the atomic percent of manganese in the MPEA filler material may be selected based on the atomic percent of iron, cobalt, and copper in the MPEA filler material. In an example, the atomic percent of manganese in the MPEA filler material may be selected based on the desired flow characteristics of the MPEA filler material since manganese has a significant effect on the flow characteristics of the melted MPEA filter material. In an example, the atomic percent of the manganese in the MPEA filler material may be selected to cause the formation of favorable pore morphology after brazing the MPEA filler material to the substrate. It has been found that manganese may be lost due to the formation of manganese and manganese oxide vapors while brazing the MPEA filler material to the substrate and manganese diffuses quicker into the substrate than the other elements of the MPEA filler material. The loss of manganese due to the formation of vapors and diffusion may cause the formation of unfavorable pores. However, increasing the atomic percent of manganese in the MPEA filler material to be greater than 40 atomic percent may provide a buffer in composition, allowing for some loss due to vaporization and diffusion without deleterious effects. In an example, the atomic percent of manganese in the MPEA filler material may be selected based on manufacturing limitations since, generally, increasing the atomic percent of manganese in the MPEA filler material may increase the difficulty in forming the MPEA filler material.

As previously discussed, the MPEA filler material includes iron. The iron may form about 0 atomic percent to about 35 atomic percent of the MPEA filler material, such as 0 atomic percent to about 1 atomic percent, greater than 0 atomic percent to about 2 atomic percent, about 1 atomic percent to about 3 atomic percent, about 2 atomic percent to about 4 atomic percent, about 3 atomic percent to about 5 atomic percent, about 4 atomic percent to about 6 atomic percent, about 5 atomic percent to about 7.5 atomic percent, about 7 atomic percent to about 10 atomic percent, about 7.5 atomic percent to about 12.5 atomic percent, about 10 atomic percent to about 15 atomic percent, about 12.5 atomic percent to about 17.5 atomic percent, about 15 atomic percent to about 20 atomic percent, about 17.5 atomic percent to about 22.5 atomic percent, about 20 atomic percent to about 25 atomic percent, about 22.5 atomic percent to about 27.5 atomic percent, about 25 atomic percent to about 30 atomic percent, about 27.5 atomic percent to about 32.5 atomic percent, or about 30 atomic percent to about 35 atomic percent. The atomic percent of iron in the MPEA filler material may be selected based on a number of factors. In an example, as previously discussed, the atomic percent of iron in the MPEA filler material may be selected based on the desired melting temperature of the MPEA filler material since, generally, increasing the atomic percent of iron in the MPEA filler material increases the melting temperature of the MPEA filler material and vice versa. It has been found that, generally, iron has little to no effect on the melting temperature of the MPEA filler material when the atomic percent of iron in the MPEA filler material is less than 3 atomic percent. As such, in some embodiments, the atomic percent of iron in the MPEA filler material is selected to be less than 3 atomic percent which allows greater flexibility in selecting the atomic percent of the other elements in the MPEA filler material. In an example, the atomic percent of iron in the MPEA filler material may be selected to prevent the formation of brittle phases after brazing the MPEA filler material to the substrate. It has been found that iron, along with cobalt, may segregate into dendritic structures. During brazing, when the substrate includes chromium, chromium generally preferentially segregates into the dendritic structures of the MPEA filler material and does not form a brittle phase. As such, the atomic percent of iron in the MPEA filler material may be selected based on the amount of cobalt in the MPEA filler material, whether the substrate includes chromium, and the desired about of dendritic structures formed in the MPEA filler material.

As previously discussed, the MPEA filler material includes cobalt. The cobalt may form about 0 atomic percent to about 35 atomic percent of the MPEA filler material, such as 0 atomic percent to about 2.5 atomic percent, greater than 0 atomic percent to about 5 atomic percent, about 2.5 atomic percent to about 7.5 atomic percent, about 5 atomic percent to about 10 atomic percent, about 7.5 atomic percent to about 12.5 atomic percent, about 10 atomic percent to about 15 atomic percent, about 12.5 atomic percent to about 16 atomic percent, about 15 atomic percent to about 17 atomic percent, about 16 atomic percent to about 18 atomic percent, about 17 atomic percent to about 19 atomic percent, about 18 atomic percent to about 20 atomic percent, about 19 atomic percent to about 22.5 atomic percent, about 20 atomic percent to about 25 atomic percent, about 22.5 atomic percent to about 27.5 atomic percent, about 25 atomic percent to about 30 atomic percent, about 27.5 atomic percent to about 32.5 atomic percent, or about 30 atomic percent to about 35 atomic percent. The atomic percent of cobalt in the MPEA filler material may be selected based on a number of factors. In an example, as previously discussed, the atomic percent of cobalt in the MPEA filler material may be selected based on the desired melting temperature of the MPEA filler material since, generally, increasing the atomic percent of cobalt in the MPEA filler material increases the melting temperature of the MPEA filler material and vice versa. Generally, it has been found that keeping the atomic percent of cobalt below 19 atomic percent (e.g., 15 atomic percent to 19 atomic percent) prevents the cobalt from increasing the melting temperature too much without having to increase the quantity of manganese in the MPEA filler material to the extent that the manufacturability of the MPEA filler material is adversely affected or having to increase the quantity of copper in the MPEA filler material to the extent that copper is likely to form a secondary phase in the MPEA filler material.

As previously discussed, the MPEA filler material includes nickel. The nickel may form about 0 atomic percent to about 35 atomic percent of the MPEA filler material, such as 0 atomic percent to about 2.5 atomic percent, greater than 0 atomic percent to about 5 atomic percent, about 2.5 atomic percent to about 7.5 atomic percent, about 5 atomic percent to about 10 atomic percent, about 7.5 atomic percent to about 12.5 atomic percent, about 10 atomic percent to about 15 atomic percent, about 12.5 atomic percent to about 16 atomic percent, about 15 atomic percent to about 17 atomic percent, about 16 atomic percent to about 18 atomic percent, about 17 atomic percent to about 19 atomic percent, about 18 atomic percent to about 20 atomic percent, about 19 atomic percent to about 22.5 atomic percent, about 20 atomic percent to about 25 atomic percent, about 22.5 atomic percent to about 27.5 atomic percent, about 25 atomic percent to about 30 atomic percent, about 27.5 atomic percent to about 32.5 atomic percent, or about 30 atomic percent to about 35 atomic percent. Nickel has significantly less effect on the melting temperature of the MPEA filler material than manganese, iron, and cobalt. However, nickel helps facilitate bonding of the MPEA filler material to the substrate since the substrate may include nickel. For example, the presence of nickel in the MPEA filler material facilitates accommodation of elements from the substrate, such as nickel and chromium, into the MPEA filler material. However, increasing the atomic percent of nickel in the MPEA filler material may dilute the strengthening effect offered by severe lattice distortion in the MPEA filler material. Furthermore, the inventors have found that there is likely to already be a significant influx of nickel from the substrate if the substrate contains nickel, requiring the nickel content of the MPEA filler material itself be kept low enough to prevent excessive dilution in nickel. Generally, the atomic percent of nickel in the MPEA filler material is selected to be less than 19 atomic percent to prevent these issues though, depending on the composition of the MPEA filler material and the substrate, the atomic percent of nickel in the MPEA filler material may be greater than 19 atomic percent.

As previously discussed, the MPEA filler material includes copper. The copper may form about 0 atomic percent to about 35 atomic percent of the MPEA filler material, such as 0 atomic percent to about 2.5 atomic percent, greater than 0 atomic percent to about 5 atomic percent, about 2.5 atomic percent to about 7.5 atomic percent, about 5 atomic percent to about 10 atomic percent, about 7.5 atomic percent to about 12.5 atomic percent, about 11 atomic percent to about 13 atomic percent, about 12 atomic percent to about 14 atomic percent, about 13 atomic percent to about 15 atomic percent, about 14 atomic percent to about 16 atomic percent, about 15 atomic percent to about 17 atomic percent, about 16 atomic percent to about 18 atomic percent, about 17 atomic percent to about 19 atomic percent, about 18 atomic percent to about 20 atomic percent, about 19 atomic percent to about 21 atomic percent, about 20 atomic percent to about 25 atomic percent, about 22.5 atomic percent to about 27.5 atomic percent, about 25 atomic percent to about 30 atomic percent, about 27.5 atomic percent to about 32.5 atomic percent, or about 30 atomic percent to about 35 atomic percent. The atomic percent of copper in the MPEA filler material may be selected based on a number of factors. In an example, as previously discussed, the atomic percent of copper in the MPEA filler material may be selected based on the desired melting temperature of the MPEA filler material since, generally, increasing the atomic percent of copper in the MPEA filler material decreases the melting temperature of the MPEA filler material and vice versa. Also, it has been found that increasing the atomic percent of copper in the MPEA filler material increases the likelihood that the MPEA filler material forms a potentially detrimental secondary phase. As such, the atomic percent of copper in the MPEA filler material may be selected based on balancing the need to decrease the melting temperature of the MPEA filler material while preventing the formation of secondary phases. It has been found that maintaining the atomic percent of copper between about 13 atomic percent and 18 atomic percent, in most instances, is sufficient to prevent the formation of secondary phases while also sufficiently suppressing the melting temperature of the MPEA filler material.

The MPEA filler material may include one or more additional materials. Examples of additional materials that may be included in the MPEA filler material include, but are not limited to, aluminum, titanium, and niobium. In an embodiment, each additional material may form about 1 atomic percent to about 5 atomic percent of the MPEA filler material, such as about 1 atomic percent to about 3 atomic percent, about 2 atomic percent to about 4 atomic percent, or about 3 atomic percent to about 5 atomic percent. The additional material may affect at least one of the melting temperature of the MPEA filler material, prevent or inhibit loss of manganese, prevent or inhibit oxidation of the MPEA filler material, improve bonding between the MPEA filler material and the substrate, improve the mechanical properties of the MPEA filler material, or inhibit the formation of secondary phases.

The MPEA filler material may include at least one of one or more oxides or one or more carbides, as a result of metallic elements reacting with oxygen or carbon within the MPEA filler material. Generally, it is desirable to limit the quantity of oxides and carbides in the MPEA filler material since the oxides and carbides prevent the MPEA filler material from exhibiting a single phase. However, the MPEA filler material may have oxides and carbides due to impurities present in the starting material, impurities introduced during manufacturing of the MPEA filler material, and due to the MPEA filler material being exposed to the environment. To limit the effect that the oxides and carbides have on the MPEA filler material, the atomic percent of each of oxygen and carbon are selected to be about 1 atomic percent or less and, more preferably, about 0.5 atomic percent or less. It is noted that one or more exterior surface of the MPEA filler material may need to be removed (e.g., grinded) periodically to remove a surface oxide layer to keep the oxygen in the MPEA filler material below about 1 atomic percent.

In an embodiment, the MPEA filler material is substantially free of silicon, boron, and phosphorus which prevents the formation of brittle phases (e.g., silicides and borides) in the MPEA filler material or after the MPEA filler material is brazed to the substrate. However, it is noted that the MPEA filler material may include negligible amounts of at least one of silicon, boron, or phosphorus since, for example, silicon, boron, or phosphorus may be present as impurities in the base materials used to form the MPEA filler material or may be introduced into the MPEA filler material during manufacture of the MPEA filler material (e.g., removing oxides from the MPEA filler material using silicon carbide grinding pads may introduce silicon into the MPEA filler material). The MPEA filler material is considered to have negligible amounts of silicon, boron, or phosphorus when the MPEA filler material includes, at most 1 atomic percent and, more preferably at most 0.5 atomic percent or at most 0.1 atomic percent of each of silicon, boron, and phosphorus. When the quantities of silicon, boron, or phosphorus are below 1 atomic percent and, more preferably at most 0.5 atomic percent or at most 0.1 atomic percent no significant secondary phases containing silicon, boron, or phosphorus have been detected in the MPEA filler material or in the braze joint formed with the MPEA filler material.

The MPEA filler material may include one or more impurities therein. As previously discussed, the impurities may include silicon, boron, phosphorus, oxygen, and carbon. The impurities may also include aluminum, titanium, nitrogen, magnesium, sulfur, chlorine, calcium, chromium, zinc, gallium, germanium, arsenic, molybdenum, niobium, gold, silver, palladium, indium, tin, tungsten, platinum, lead, any other element, or combinations thereof. Each of the impurities may be present in the MPEA filler material at about 1 atomic percent or less, such as about 0.75 atomic percent or less, about 0.5 atomic percent or less, about 0.4 atomic percent or less, about 0.3 atomic percent or less, about 0.2 atomic percent or less, about 0.15 atomic percent or less, about 0.1 atomic percent or less, or about 0.05 atomic percent or less to minimize the effect that each impurity has on the properties of the MPEA filler material. Collectively, the impurities may be present in the MPEA filler material at about 5 atomic percent or less, about 4.5 atomic percent or less, about 4 atomic percent or less, about 3.5 atomic percent or less, about 3 atomic percent or less, about 2.5 atomic percent or less, about 2 atomic percent or less, about 1.75 atomic percent or less, about 1.5 atomic percent or less, about 1.25 atomic percent or less, about 1 atomic percent or less, about 0.8 atomic percent or less, about 0.6 atomic percent or less, or about 0.5 atomic percent or less to minimize the effect that the collective impurities have on the properties of the MPEA filler material.

It is noted that, generally, the compositions of the MPEA filler materials disclosed herein refers to the composition of the MPEA filler material before brazing the MPEA filler material to a substrate since brazing may change the composition of the MPEA filler material due to interactions with the substrate, evaporation, etc. However, in some embodiments, the compositions of the MPEA filler material disclosed herein may also refer to the composition of the MPEA filler material after brazing the MPEA filler material to the substrate since the composition of the MPEA filler material may still fall within the disclosed ranges even after changing the composition of the MPEA filler material during brazing.

The MPEA filler material may exhibit a relatively high configurational entropy, such as an entropy of about 10 J/mol*K to about 20 J/mol*K, such as about 10 J/mol*K to about 12 J/mol*K, about 11 J/mol*K to about 13 J/mol*K, about 12 J/mol*K to about 14 J/mol*K, about 13 J/mol*K to about 15 J/mol*K, about 14 J/mol*K to about 16 J/mol*K, about 15 J/mol*K to about 17 J/mol*K, about 16 J/mol*K to about 18 J/mol*K, about 17 J/mol*K to about 19 J/mol*K, or about 18 J/mol*K to about 20 J/mol*K. In a particular embodiment, the MPEA filler material may exhibit an entropy of about 12 J/mol*K to about 17.5 J/mol*K. The relatively high configurational entropy of the MPEA filler material may stabilize substantially only a single disordered solid solution phase in the MPEA filler material which, in turn, inhibits the formation of intermetallic compounds that would weaken the MPEA filler material. Further, the relatively high configurational entropy of the MPEA filler material may help stabilize the single disordered solid solution phase as the MPEA filler material is heated, such as during brazing, and also may prevent the formation of secondary phases that may weaken a braze joint formed with the MPEA filler material. It is noted that increasing the number of constituents in the MPEA filler material may also help stabilize the single disordered solid solution phase.

Unlike conventional alloys, the MPEA filler material may exhibit a fluctuation in potential energy between specific lattice sites thereof due to the fact that the combination of atoms neighboring a particular site can vary tremendously through the lattice. The potential energy fluctuations may cause certain atoms to become trapped at low lattice potential sites which, in turn, slows the diffusion kinetics through the MPEA filler material. The slowed diffusion kinetics of the MPEA filler material may limit the interdiffusion of atoms from the substrate which may prevent or at least inhibit the formation of secondary phases that may adversely affect the properties of the braze joints formed with the MPEA filler material. It is noted that the slowed diffusion kinetics of the MPEA filler material may only be present when the MPEA filler material is in a solid state and may not apply when the MPEA filler material is in a molten state.

The MPEA filler material may exhibit a severe lattice distortion without the application of any extrinsic strain. The severe lattice distortion may be quantified according to the average atomic size difference, which may be up to 6 percent of the mean atomic radius without promoting the formation of secondary phases which may adversely affect properties of the MPEA filler material. The severe lattice distortion may be caused by atomic size mismatch between neighboring atoms. The severe lattice distortion may cause the MPEA filler material to exhibit excellent solid solution strengthening behavior, particular at high temperatures, where the single-phase structure of the MPEA filler material remains stable. The solid solution strengthening behavior of the MPEA filler material may form high-strength braze joints with high temperature stability.

The MPEA filler material may exhibit a cocktail effect with regards to the melting temperature thereof. For example, the melting temperature of the MPEA filler material trends towards the weighted average of the properties of its constituents. This cocktail effect allows relative control of the melting temperature of the MPEA filler material by modifying the atomic percent of each element of the MPEA filler material. Controlling the melting temperature of the MPEA filler material allows the brazing temperature to be easily selected.

The MPEA filler material may exhibit a melting temperature that is about 950° C. or greater, about 1000° C. or greater, about 1050° C. or greater, about 1100° C. or greater, about 1150° C. or greater, about 1200° C. or greater, about 1250° C. or greater, about 1300° C. or greater, about 1350° C. or greater, or in ranges of about 950° C. to about 1050° C., about 1000° C. to about 1100° C., about 1050° C. to about 1150° C., about 1100° C. to about 1200° C., about 1150° C. to about 1250° C., about 1200° C. to about 1300° C., or about 1250° C. to about 1350° C. As previously discussed, the melting temperature of the MPEA filler material is selected to be less than the melting temperature of the substrate. For example, the melting temperature of the MPEA filler material may be selected to be less than the melting temperature of the substrate by about 50° C. or more, about 100° C. or more, about 150° C. or more, about 200° C. or more, about 250° C. or more, or in ranges of about 50° C. to about 150° C., about 100° C. to about 200° C., or about 150° C. to about 250° C.

The diffusion coefficients for the manganese, cobalt, and copper of the MPEA filler material diffusing into Ni-based Alloy 600 (e.g., Inconel 600) at 1200° C. is about 1×10⁻¹⁴m²/s to about 400×10⁻¹⁴m²/s, such as about 1×10⁻¹⁴m²/s to about 3×10⁻¹⁴m²/s, about 2×10⁻¹⁴m²/s to about 4×10⁻¹⁴m²/s, about 3×10⁻¹⁴m²/s to about 5×10⁻¹⁴m²/s, about 4×10⁻¹⁴m²/s to about 6×10⁻¹⁴m²/s, about 5×10⁻¹⁴m²/s to about 7×10⁻¹⁴m²/s, about 6×10⁻¹⁴m²/s to about 8×10⁻¹⁴m²/s, about 7×10⁻¹⁴m²/s to about 9×10⁻¹⁴m²/s, about 8×10⁻¹⁴m²/s to about 10×10⁻¹⁴m²/s, about 9×10⁻¹⁴m²/s to about 12×10⁻¹⁴m²/s, about 10×10⁻¹⁴m²/s to about 15×10⁻¹⁴m²/s, about 12×10⁻¹⁴m²/s to about 20×10⁻¹⁴m²/s, about 15×10⁻¹⁴m²/s to about 30×10⁻¹⁴m²/s, about 25×10⁻¹⁴m²/s to about 50×10⁻¹⁴m²/s, about 40×10⁻¹⁴m²/s to about 80×10⁻¹⁴m²/s, about 75×10⁻¹⁴m²/s to about 150×10⁻¹⁴m²/s, about 125×10⁻¹⁴m²/s to about 200×10⁻¹⁴m²/s, about 175×10⁻¹⁴m²/s to about 300×10⁻¹⁴m²/s, or about 250×10⁻¹⁴m²/s to about 400×10⁻¹⁴m²/s. The diffusion coefficient of each of manganese, cobalt, and copper of the MPEA filler material diffusing into Ni-base Alloy 600 at 1200° C. will vary depending on the atomic percent of each element in the MPEA filler material. The diffusion coefficients for manganese, cobalt, and copper may be different. For example, the diffusion coefficient of manganese may be greater than cobalt and the diffusion coefficient of cobalt may be greater than copper. It is noted that the diffusion coefficient for manganese of the MPEA filler material diffusing into the Ni-base Alloy 600 at 1200° C. is about 100 times less than the diffusion coefficient for pure manganese diffusing into the Ni-base Alloy 600 at 1200° C., thereby indicating that the MPEA filler material exhibits sluggish diffusion. It is noted that nickel from the Ni-base Alloy 600 material typically diffuses into the MPEA filler material and iron may exhibit minimal diffusion.

The MPEA filler material exhibits substantially only a single disordered face-centered cubic (“FCC”) phase. The FCC phase of the MPEA filler material facilitates bonding and diffusion between the MPEA filler material and the substrate. Also, selecting the MPEA filler material to exhibit substantially only a single FCC phase prevents the formation of secondary phases, such a relatively brittle secondary phases, that may adversely affect the properties of the MPEA filler material. In an embodiment, the MPEA filler material may exhibit substantially only the single FCC phase up to the melting temperature thereof, which prevents the formation of secondary phases in the braze joint across the range of cooling rates commonly experienced during brazing.

The MPEA filler material may exhibit dendritic structures with at least one interdendritic structure between the dendritic structures. The dendritic structure may include more iron and cobalt than the interdendritic structure and the interdendritic structure may include more copper and manganese than the dendritic structure. The dendritic and interdendritic structures may include substantially the same amounts of nickel.

It has been found that the properties of the MPEA filler material and the braze joint formed thereby is dependent on the composition of the MPEA filler material. For example, depending on the atomic percent of manganese, iron, cobalt, nickel, and copper, the MPEA filler material may exhibit two FCC phases, form precipitates when heated to a temperature that is less than the melting temperature, form secondary phases when heated to a temperature that is less than the melting temperature, and/or exhibit a body-centered cubic secondary phase, among other issues. However, the MPEA filler material may exhibit over 75 million permutations if each element is varied in 1 atomic percent increments which makes experimentally determining which of the possible MPEA filler materials exhibit certain properties difficult or impossible. As such, as discussed in more detail with regards to FIG. 2, a novel method of computationally determining which MPEA filler compositions exhibit certain properties is required since, due to the sheer volume of permutations, it would be impossible to experimentally determine which composition exhibit certain properties.

In an embodiment, the MPEA filler material may be formed by pieces of its pure, constituent elements. The pure, constituent element may be substantially free of oxides prior to forming the MPEA filler material. As such, the material(s) used to form the MPEA filler material (e.g., at least partially oxidized manganese pieces) may be deoxidized prior to forming the MPEA filler material. For example, when the pieces include at least partially oxidized manganese pieces, the manganese pieces may be cleaned by rinsing the manganese pieces in 10% hydrochloric acid solution for approximately 60 seconds, followed by cleaning with deionized water and ethanol and drying with a hot air gun.

In an embodiment, the MPEA filler material may be formed by arc-melting pieces of its pure, constituent elements. In such an embodiment, the melting may be performed using an airtight arc-melting chamber affixed above a water-cooled copper hearth, employing a tungsten electrode as the heat source. The chamber may be evacuated (e.g., using a roughing pump) and backfilled with ultra-high purity (UHP) argon, other noble gas, or other non-reactive gas prior to each melt. In an example, a piece of scrap titanium was melted and held molten for approximately 20 to 30 seconds prior to each melt, to attempt to bind any oxygen remaining in the chamber and thus minimize oxide formation in the MPEA filler material. Iron, cobalt, and nickel may be easier to control in the arc melting setup due to their low vapor pressure so iron, cobalt, and nickel may combined first in a single act of the arc-melting process. Copper may then generally be added in an additional step. Due to the extremely high volatility of manganese relative to the other elements, manganese may be added to the mixture of iron, cobalt, nickel, and copper last.

The as-formed MPEA filler material of manganese, iron, cobalt, nickel, and copper may be re-melted one or more times to ensure bulk compositional homogeneity in the MPEA filler material. Occasionally the MPEA filler material may unintentionally be split into two separate molten pools during melting. When this occurs, an extra melt step may be required to rejoin the pieces into the MPEA filler material. In an embodiment, additional amounts of manganese may be added to the chamber (e.g., about 10% to about 30% more than the target amount) to account for mass loss before manganese stabilized in the MPEA filler material. Including too much manganese in the MPEA filler material may be corrected by vaporization of the manganese in subsequent flipping and/or re-melting of the MPEA filler material or by controlling the time the MPEA filler material is held in a molten state.

It is noted that the MPEA filler material may be formed using methods other than arc-melting, such as a solid-state reaction, generic melting processes (e.g. vacuum induction melting), chemical vapor deposition, or any other suitable technique. The non-arc-melting techniques may include forming the MPEA filler material in a non-oxidizing atmosphere and/or re-melting the MPEA filler material.

Forming the MPEA filler material may include performing bulk compositional analysis to determine if the composition of the MPEA filler material is correct and/or within acceptable ranges. The bulk composition analysis may include X-ray fluorescence, mass spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, or any other suitable technique.

After forming the MPEA filler material, the MPEA filler material may be formed into a particular shape. In an example, the MPEA filler material may be formed into thin foils using a cold rolling technique. In such an example, the formed MPEA filler material may be cut into smaller pieces depending on the size of the formed the MPEA filler material. The MPEA filler material may or may not be annealed prior to the cold rolling process. The MPEA filler material may then be cold or hot rolled one or more times to reduce the thickness thereof. After rolling, the edges of the rolled MPEA filler material may be removed since the rolling process may cause mild edge cracking of the MPEA filler material. It has been found the cold rolling the MPEA filler material may result in a more homogenized material compared to the unshaped MPEA filler material. In an example, the MPEA filler material may be shaped using other techniques, such as using a wire die or performing gas atomization to generate the MPEA in powder format. It is noted that at least some non-cold rolling shaping techniques of the MPEA filler material may also result in a more homogenized material compared to the unshaped MPEA filler material.

All visible oxides remaining from the casting process may be removed from the MPEA filler material after forming the MPEA filler material via grinding or any other suitable technique.

As previously discussed, the MPEA filler material may be used to form a braze joint with a substrate. For example, at least one substrate may be provided that has a gap. The gap may include a crack, void space, a cut, joint between two or more substrates, or any other gap. The substrate may include a superalloy, such as a nickel-based superalloy (e.g., Ni-base Alloy 600), or any other suitable substrate. To form the braze joint, the MPEA filler material may be at least partially disposed in or adjacent to the gap. The MPEA filler material may then be melted to a temperature above the melting temperature of the MPEA filler material and below the melting temperature of the substrate. The melted MPEA filler material may at least partially fill the gap. The components of the melted MPEA filler material and components of the substrate may diffuse into each other. For example, when the substrate is Ni-base Alloy 600 or a similar substrate, the manganese, iron, cobalt, and copper of the MPEA filler material may diffuse into the substrate and nickel and chromium of the substrate may diffuse into the MPEA filler material. The MPEA filler material may be held in the molten state for a select period of time (e.g., 1 second to 1 minute, 1 minute to 1 hour, 1 hour to 6 hours, 6 hours to 12 hours, or 12 hours to 24 hours) to allow for sufficient diffusion and bonding to occur between the MPEA filler material and the substrate. The MPEA filler material is then allowed to cool and solidify to form the braze joint. It is noted that the composition of the MPEA filler material is different after being brazed to the substrate than before the MPEA filler material is brazed to the substrate due to diffusion and other chemical reactions (e.g., oxidation).

In an embodiment, the process of brazing the MPEA filler material to the substrate may address practical issues associated with transient liquid phase (“TLP”) bonding. FIG. 1A is a set of schematic illustrations of the stage in an ideal TLP bonding process. It is noted that the phase diagrams of the MPEA filler materials disclosed herein are more complicated that the phase diagrams illustrated in FIG. 1A. However, the phase diagrams illustrated in FIG. 1A are merely provided to illustrate whether the temperature is above or below the liquid temperature or solidus temperature and how diffusion of the components changes the melting temperature.

The core principle governing TLP bonding is that fillers designed appropriately can experience complete solidification during an isothermal hold. This solidification occurs through compositional changes that result from the diffusional exchange of particular elements with the conventional filler material with addition of melting point depressants. Holding beyond the time required for complete isothermal solidification can cause subsequent homogenization, and result in a braze joint with constituent phases and compositional distribution nearly indistinguishable from that of the parent material.

In FIG. 1A(i), the assembly (i.e., the at least one substrate and the conventional filler material with melting point depressants) is brought to the bonding temperature, which is above the melting point of the conventional filler material. Partial dissolution of the substrate may then commence, enlarging the molten pool and enriching its composition with the primary substrate element (e.g., nickel), as shown in FIG. 1A(ii). This stage in known as “progressive liquation of the base metal” and note that it is convection-controlled. The composition of the adjacent solid may theoretically be brought to the composition on the solidus curve at the bonding temperature, creating local solid-liquid equilibrium. This often fails to occur in practice and accounts for deviations from ideal TLP behavior. Once the liquid phase becomes saturated in the primary substrate element, isothermal solidification may commence, as shown in FIG. 1A(iii). Isothermal solidification may be controlled by the solid-state diffusion of the melting point depressant in the filler material into the substrate, which brings the local melting temperature above the isothermal hold. As the assembly continues to be held at the bonding temperature, isothermal solidification completes. The composition gradient at the interface can be subsequently homogenized either partially or fully. The TLP models assumes this procedure occurs purely sequentially, since the reactions usually occur at high temperatures and over an extended period of time. Thus, the models neglect to predict the possible formation of secondary phases at the bonding temperature resulting from occurrence of the stages in parallel, which often happens in practical TLP processes, as shown in FIG. 1A-(iv). The time to the onset of isothermal solidification is almost always on the order of a few minutes for TLP processes. However, as the rate of solidification is governed by the solid-state diffusion rate of an element into a particular substrate, the time to complete isothermal solidification can very drastically.

With conventional filler materials, failing to hold the assembly at the bonding temperature for sufficient duration to allow for complete isothermal solidification can significantly increase the extent of brittle second phases formed during cooling, as shown in FIG. 1A(iv). The MPEA filler materials disclosed herein do not require complete isothermal solidification. For example, FIG. 1B is a set of schematic illustrations of the stages of the bonding process with the MPEA filler. In FIG. 1B(i), the assembly (i.e., the at least one substrate and the MPEA filler material) is brought to the bonding temperature, which is above the melting point of the MPEA filler material. As shown in FIG. 1B(ii), the assembly may undergo progressive liquidation of the base material during the brazing process for the MPEA filler. However, the MPEA filler is not designed to experience complete isothermal solidification, since it is unnecessary for the MPEA to exhibit a lack of secondary phases, as shown in FIGS. 1B(iii) and 1B(iv). Therefore, the ability of the MPEA filler to avoid secondary phase formation irrespective of the extent of isothermal solidification is an advantage to overcome this challenge of TLP processes.

After brazing the MPEA filler material to a substrate, the portions of the braze joint formed from the MPEA filler material may display dendritic solidification behavior, depending on the cooling rate during the brazing process. The portions of the braze joint formed from the MPEA filler material exhibits a structure including dendrites and interdendrites. The grains of the portions of the braze joint formed from the MPEA filler material may be columnar in nature, a single orientation that may pervade multiple primary dendrites. Manganese and copper may segregate to interdendritic space and iron and cobalt may segregate to the dendrites. Nickel displays little preference for either the dendritic or interdendritic spaces. The manganese segregation may indicate that a degree of re-homogenization occurred while the solid filler was still exposed to high temperatures during cooling. In an embodiment, portions of the braze joint formed from the MPEA filler material may include chromium that diffused from the substrate during the brazing process. Such diffused chromium may have a strong preference to segregate to dendritic structure. It is noted that the diffused chromium may not prevent the portions of the braze joint formed from the MPEA filler material from exhibiting an FCC phase which indicates that at least some of the MPEA filler materials disclosed herein may exhibit some degree of tolerance to chromium-diffusion without forming large precipitates of the detrimental chromium-rich sigma phase. This tolerance may be dependent upon the careful process control offered by vacuum furnace brazing.

In an embodiment, the braze joint may exhibit epitaxial growth across the filler-substrate interface. The epitaxial growth behavior indicates that there is a sufficient lattice parameter match in the FCC phases displayed by the braze joint and substrate for epitaxy to occur. In an embodiment, several of the grains in the filler may exhibits a similar orientation to an adjacent substrate grain with a layer of fine filler grains between the grains of the filler material exhibiting an orientation similar to the adjacent substrate grain and the substrate grain. In such an embodiment, the finer filler grains may be formed due to recrystallization during cooling, induced by thermal expansion mismatch at the material interface.

In an embodiment, the morphology of the portions of the braze joint formed from the MPEA filler material is modified by allowing the substrate to weigh freely upon the molten MPEA filler material, providing a squeeze effect. Such MPEA filler material and the portions of the braze joint formed from the MPEA filler material is referred to as “compressed filler.” In such an embodiment, finer, equiaxed grains are present in the compressed filler, with no dendritic substructure. This modified morphology of the compressed filler may be attributable to the weight-induced compressive pressure and centerward liquid flow generated from the squeeze effect. This causes changes in gap width and the volume of molten filler occupying the gap. The element segregation behavior is similar, with manganese and copper co-segregating, while iron, cobalt, and diffused chromium segregate to the alternative regions. As such, copper and manganese rich segregation may line the grain boundaries in this filler morphology, particularly those near the joint centerline. The equiaxed grains solidified by rejecting copper and manganese as low-melting point “solutes”, pushing these elements to grain boundaries.

The MPEA filler material may have no or negligible compressive forced applied thereto when being brazed to the substrate. Such MPEA filler material and the portions of the braze joint formed from the MPEA filler material is referred to as “fixed-gap-width filler.” The compressed filler may exhibit more equiaxed and finer grains than the fixed-gap-width filler, thereby causing the compressed filler to exhibit better mechanical performance of the fixed-gap-width filler. For example, equiaxed, relatively finer grains offered by the compressed filler should give joints including the compressed filler higher strength and more isotropic properties than if the joint included the fixed-gap-width filler.

The compressed filler may exhibit a markedly higher occurrence of twinning than the fixed-gap-width filler. The difference in twinning between the compressed filler and the fixed-gap-width filler may be caused by the compressive stresses applied to the compressed filler impacting the annealing behavior immediately below the melting temperature range of the filler and/or differences in the local thermal history during cooling resulting from the discrepancy in filler thickness.

Anneal twinning at the interface is more frequently observed in the compressed-filler configuration. This is a mechanism to lower the interfacial energy at the dissimilar material boundary. Anneal twinning may have also accommodated weight-induced stresses in the compressed-filler configuration.

The braze joint may exhibit a shear strength that is about 200 MPa or greater, about 225 MPa or greater, about 250 MPa or greater, about 275 MPa or greater, about 300 MPa or greater, about 325 MPa or greater, about 350 MPa or greater, about 375 MPa or greater, about 400 MPa or greater, about 450 MPa or greater, about 500 MPa or greater, about 600 MPa or greater, or in ranges of about 200 MPa to about 250 MPa, about 225 MPa to about 275 MPa, about 250 MPa to about 300 MPa, about 275 MPa to about 325 MPa, about 300 MPa to about 350 MPa, about 325 MPa to about 375 MPa, about 350 MPa to about 400 MPa, about 375 MPa to about 450 MPa, about 400 MPa to about 500 MPa, or about 450 MPa to about 600 MPa. The shear strength of the braze joint may depend on the composition of the MPEA filler material, the composition of the substrate, and the amount of diffusion between the MPEA filler material and the substrate (e.g., on the braze temperature and the time that the MPEA filler material is held as the braze temperature). The shear strength of the braze joints may be selected based on the application that the substrate is used in.

As previously discussed, a novel method of computationally determining which MPEA filler compositions exhibit certain properties is required since, due to the sheer volume of permutations, it would be nearly impossible to experimentally determine which composition exhibit certain properties. FIG. 2 is a flow chart of the method 200, according to an embodiment. The method 200 includes block 205, which includes using a parameter-based filtration series modelled to screen many distinct MPEA systems simultaneously and selecting the MPEA systems which fit the desired parametric requirements across the broadest range of specific compositions. The method 200 also includes block 210, which includes screening compositions within a particular selected MPEA system and selecting those composition(s) that are predicted to display the most desirable solidification behavior for brazing. Desirable attributes of the solidification behavior were a relatively low melting point and narrow solidification temperature range. The method 100 may also include block 215, which includes predicting filler-substrate interactions for at least some of the selected compositions through the construction of isopleth phase diagrams.

The method 200 includes block 205, which includes using a parameter-based filtration series modelled to screen many distinct MPEA systems simultaneously and selecting the MPEA systems which fit the desired parametric requirements across the broadest range of specific compositions. In an example, the block 205 includes the construction of the composition space beginning by selecting one or more of at least one transition metal element (e.g., titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, etc.) or at least one post-transition metal element (e.g., aluminum), such as between 9 and 13 transition metal elements and/or post-transition metal elements. Block 205 further includes constructing all of the quinary systems that could be formed from these elements. For simplicity, only quinary systems are discussed herein though, it is noted, systems with any number of elements may be used in the method 200. For clarification, as it pertains to method 200, a system is taken to mean a unique combination of elements from which specific MPEA compositions can be subsequently selected. The combinatorics may results in 126 or more unique quinary systems (₉C₅) when the selected transition metal element or at least one post-transition metal element include aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper. A uniqueness condition may be required to limit the number of candidate compositions to a set that could be screened in a reasonable amount of computation time. To this end, compositions differing from one another by a minimum of 1 atomic percent in any constituent element may be defined as unique. Imposing the condition that the atomic concentrations were required to sum to 100%, this variation may produce an initial set in excess of 550,000 compositions for a given alloy system.

Filtration code designed to initially construct this composition space for all quinary systems that may be constructed from a set of input elements. Elements may be inputted along with at least data on their atomic radius, their valence electron concentration (VEC), and the enthalpy of mixing (ΔH_mix).

All compositions for each of the systems may be checked to see whether each system satisfies one or more (e.g., all) parameters. In an example, the parameters may include an atomic size mismatch δ>6.0% (e.g., according to the equation δ=√{square root over (Σ_i=1ⁿc_i*(1−r_i/r))}), a VEC>8 (e.g., according to the equation VEC=Σ_i=1ⁿc_i(vec)_i), a configuration entropy ΔS_mixof about 12 J/mol*K to about 17.5 J/mol*K (e.g., according to the equation ΔS_mix=R*Σ_i=1ⁿc_iln(c_i)), or an enthalpy of mixing ΔH_mixof about −15 kJ/mol to +5 kJ/mol (e.g., according to the equation ΔH_mix=4*Σ_i=1,i≠jⁿ(ΔH_mix)_ijc_ic_j). Using the TiMnCoNiCu element combination as an example, the above noted parameters result in 37.8% of the initial composition pool remaining. The ranges provided in the above example may be favorable for a single-phase FCC crystal structure which may match the microstructure of Alloy 600. However, it is noted that the same process could be employed with altered filtration criteria to target either BCC or mixed-phase microstructures, if desired. At each filtration step, compositions that failed to meet the associated criterion may be discarded, for example, by removing the failed compositions from the enumeration of possible compositions. It is noted that other parameters may be selected, such as an atomic size mismatch of less than 10% (e.g., less than 7%, less than 5%, or less than 3%), a VEC that is about 5 or more (e.g., about 6 or more, about 9 or more, or about 10 or more), a configuration entropy of about 10 J/mol*K to about 20 J/mol*K (e.g., about 10 J/mol*K to about 15 J/mol*K or about 15 J/mol*K to about 20 J/mol*K), an enthalpy of mixing of about −20 kJ/mol to about +10 kJ/mol (e.g., about −20 kJ/mol to about −0 kJ/mol or about −10 kJ/mol to about +10 kJ/mol).

In addition to eliminating certain systems, the filtration procedure may provide insight regarding which of the remaining systems hold promise for filler alloy development. For example, the MnFeCoNiCu system may have the highest overall pass rate when the selected elements include aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, and copper and the parameters are an atomic size mismatch δ>6.0%, a VEC>8, a configuration entropy ΔS_mixof about 12 J/mol*K to about 17.5 J/mol*K, and an enthalpy of mixing ΔH_mixof about −15 to +5 kJ/mol.

After block 205, the method 200 may include block 210. Block 210 includes screening compositions within a particular selected MPEA system and selecting those composition(s) that are predicted to display the most desirable solidification behavior for brazing. Within a selected alloy system, some of the most important criteria for establishing the viability of a particular composition as a braze filler are the liquidus temperature and solidification temperature range. It is essential that the filler liquidus temperature be kept sufficiently below the solidus of the substrate material (e.g., the superalloy) that a brazing temperature can be selected at which the filler completely melts and the substrate remains entirely solid. Narrowing the solidification range is also considered desirable in the development of filler alloys, as it reduces the likelihood of solidification cracking of the superalloy and offers more uniform flow characteristics.

Pseudo-binary phase diagrams can offer insight into how compositional alterations can influence these aspects of solidification behavior, but only while altering atomic concentrations of each element two at a time. To rigorously optimize an MPEA composition, a high-throughput means of comparing the predicted solidification behavior while altering the atomic concentration of all the elements may be required. To this end, in an embodiment, the Scheil solidification module of ThermoCalc may be implemented en masse through the TC-Python interface, constituting block 210. The Scheil module may provide the fastest and simplest means of comparing the solidification behavior for pure filler candidates as composition is varied.

In a particular embodiment, ThermoCalc's TCHEA3 database for MPEAs may be used to conduct the Scheil simulations, which were set to initiate at a solid phase fraction of 10% and terminate at a solid phase fraction of 90%. These limits may be selected to avoid calculations near the immediate onset and termination of solidification thereby reducing the simulation failure rate and allowing for en masse implementation to proceed more smoothly. A valid qualitative comparison among the input compositions may be performed by taking the temperature at 10% solid fraction as an approximation of the liquidus, and the temperature at 90% solid fraction as the approximate solidus.

Compositions that successfully passed all stages of screening from block 205 may be used as inputs for block 210. In an embodiment, the curves generated during block 210 (e.g., from the Scheil simulation) may be screened by eliminating curves that are not entirely above a selected temperature (e.g., 1250° C. which provides a temperature buffer of 100° C. for brazing temperature selection) and include sharp discontinuity in their solidification curves, as the discontinuity is usually a signature of latent heat release during a phase transformation.

For example, examining the MnFeCoNiCu system, 280 compositions exist which have a manganese concentration of 35 atomic percent and an iron concentration of 5 atomic percent and the concentration of cobalt, nickel, and copper are allowed to vary. The curves resulting from the Scheil simulation of these compositions are shown in FIG. 3A with a line at the selected temperature of 1250° C. FIG. 3B is a histogram of the approximate liquidus temperatures for all 280 components. The output of the Scheil simulation of five specific example compositions, a subset of a larger set of the compositions possibly suitable, are illustrated in FIG. 3C. These compositions include Mn₃₅Fe₅Co₁₁Ni₂₁Cu₂₈, Mn₃₅Fe₅Co₁₁Ni₂₈Cu₂₁, Mn₃₅Fe₅Co₂₀Ni₂₀Cu₂₀, Mn₃₅Fe₅Co₂₂Ni₂₂Cu₁₆, and Mn₃₅Fe₅Co₃₀Ni₁₆Cu₁₆. These compositions are included to illustrate the variability of output among compositions within the 280 choices previously described. Of the 280 compositions, Mn₃₅Fe₅Co₁₁Ni₂₁Cu₂₈has the narrowest solidification temperature range and Mn₃₅Fe₅Co₁₁Ni₂₈Cu₂₁has the lowest liquidus temperature.

After block 210, the method 200 may include block 215. Block 215 includes predicting filler-substrate interactions for at least some of the selected compositions through at least one of the construction of isopleth phase diagrams. The phases that form upon solidification of pure filler material may be substantially different from those that form when the material is in contact with the substrate, particularly if the substrate contains highly reactive elements. Block 215 may be the stage of numerical investigation (e.g., at which individual CALPHAD diagrams may be used) to study the expected behavior of particular compositions selected after one or more of blocks 205 or 210 and their interactions with the substrate.

In an example, an isopleth in ThermoCalc CALPHAD software may be used to model filler-substrate interactions. This type of phase diagram holds the ratios between certain element concentrations constant, while allowing a single element concentration to vary. Such a diagram can be used to model the phase behavior when an initial filler composition becomes increasingly infused with elements that are present in higher concentrations in the substrate material being brazed.

Two examples of isopleths are shown in FIGS. 4A and 4B for Mn₃₅Fe₅Co₂₀Ni₂₀Cu₂₀. The primary substrate elements that diffuse into the MPEA filler region from Ni-base Alloy 600 are Ni and Cr. FIG. 4A holds the relative ratio of Mn:Fe:Co:Cu constant while allowing the total nickel concentration to increase from the pure MPEA value of 20 atomic percent, which lies at the left side of the diagram. As shown, diffused nickel from the substrate has a mild impact upon the equilibrium thermodynamics of the MPEA system, as the only solid phase expected to form remains a single disordered FCC solid solution. However, increasing the nickel concentration to 40 atomic percent is predicted to cause a 50-60° C. increase in both the solidus and liquidus temperature of the alloy. The liquidus is elevated to 1200° C., which may be the optimum brazing temperature.

The MPEA filler Mn₃₅Fe₅Co₂₀Ni₂₀Cu₂₀(labeled as “pure MPEA” in FIG. 4B) contains no chromium prior to brazing, so FIG. 4B models the phase behavior upon increasing the chromium content from 0 atomic percent, while holding the ratio of all the original elements in the MPEA constant. Unlike an increase in nickel content, the introduction of chromium dramatically alters the phase equilibria within the system. Above temperatures of 700° C. and below the solidus line, a second FCC solid solution phase is predicted to form as the chromium content increases beyond roughly 5 atomic percent, with the specific solvus composition dependent upon the temperature. As the chromium content is elevated above 10-15 atomic percent, a BCC solid solution is predicted to form as well. Below 700° C., the diagram predicts parallel behavior in the solid solution phases, but an ordered phase dubbed sigma is also predicted to be stable, even at very low chromium content. This phase is analogous to the sigma-phase that readily forms in stainless steels at a chromium-content greater than 20 weight percent ThermoCalc predicts sigma phase to be rich in chromium and cobalt.

Considering that the concentration of chromium in the Ni-base Alloy 600 alloy is only around 15 atomic percent, it is quite unlikely that enough diffused chromium would ever be present in the MPEA filler to promote the stability of a BCC phase. This is especially true seeing as chromium diffusion occurs concurrently with dilution of the MPEA in nickel, which is present in the substrate at a substantially larger concentration. However, the diffusion of enough chromium to promote the formation of sigma phase is a very real possibility for this composition.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting.

Terms of degree (e.g., “about,” “substantially,” “generally,” etc.) indicate structurally or functionally insignificant variations. In an example, when the term of degree is included with a term indicating quantity, the term of degree is interpreted to mean ±10%, ±5%, or ±2% of the term indicating quantity. In an example, when the term of degree is used to modify a shape, the term of degree indicates that the shape being modified by the term of degree has the appearance of the disclosed shape. For instance, the term of degree may be used to indicate that the shape may have rounded corners instead of sharp corners, curved edges instead of straight edges, one or more protrusions extending therefrom, is oblong, is the same as the disclosed shape, etc.

Claims

1. A multi-principal element alloy (“MPEA”) filler material, comprising:

manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material;

iron at 0 atomic percent to about 3 atomic percent of the MPEA filler material;

cobalt at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material;

nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material; and

copper at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material.

2. The MPEA filler material of claim 1, wherein the manganese at about 40 atomic percent to about 50 atomic percent of the MPEA filler material.

3. The MPEA filler material of claim 1, wherein the cobalt at about 15 atomic percent to about 19 atomic percent of the MPEA filler material.

4. The MPEA filler material of claim 1, wherein the nickel at about 15 atomic percent to about 19 atomic percent of the MPEA filler material.

5. The MPEA filler material of claim 1, wherein the copper at about 13 atomic percent to about 18 atomic percent of the MPEA filler material.

6. The MPEA filler material of claim 1, further comprising aluminum at about 1 atomic percent to about 5 atomic percent of the MPEA filler material.

7. The MPEA filler material of claim 1, further comprising titanium at about 0.5 atomic percent to about 5 atomic percent of the MPEA filler material.

8. The MPEA filler material of claim 1, wherein the MPEA filler material is substantially free of silicon.

9. The MPEA filler material of claim 1, wherein the MPEA filler material is substantially free of boron.

10. The MPEA filler material of claim 1, wherein the MPEA filler material exhibits a single phase face-centered cubic structure.

11. The MPEA filler material of claim 1, wherein the MPEA filler material exhibits dendritic structures and interdendritic structures.

12. The MPEA filler material of claim 11, wherein the dendritic structures include more iron and cobalt than the interdendritic structures and the interdendritic structures include more manganese and copper than the dendritic structures.

13. A braze joint, comprising:

a first substrate at least partially defining a gap;

the MPEA filler material of claim 1 at least one of disposed in at least a portion of the gap or at least partially diffused into the first substrate.

14. The braze joint of claim 13, wherein the MPEA filler material is at least partially diffused into the first substrate.

15. The braze joint of claim 13, wherein the MPEA filler material is a compressed filler.

16. The braze joint of claim 13, wherein the MPEA filler material is a fixed-gap-width filler.

17. A multi-principal component alloy (“MPEA”) filler material, comprising:

manganese at about 10 atomic percent to about 60 atomic percent of the MPEA filler material;

iron at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material;

cobalt at greater than 0 atomic percent to about 19 atomic percent of the MPEA filler material;

nickel at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material; and

copper at greater than 0 atomic percent to about 35 atomic percent of the MPEA filler material.

18. A braze joint, comprising:

a first substrate at least partially defining a gap;

the MPEA filler material of claim 17 at least one of disposed in at least a portion of the gap or at least partially diffused into the first substrate.

19. A method of determining materials for a multi-principal component alloy (“MPEA”) filler material, the method comprising:

using a parameter-based filtration series modelled to screen a plurality of distinct MPEA systems and selecting the MPEA systems which fit one or more desired parametric requirements;

screening compositions within a particular selected MPEA system and selecting one or more compositions that are predicted to display desirable solidification behavior for brazing, wherein the desirable attributes of the solidification behavior include at least one of a selected melting point or a selected solidification temperature range; and

predicting interactions between the MPEA filler material and a substrate for at least some of the selected compositions through construction of isopleth phase diagrams.