METHODS OF MAKING AND TREATING COPPER-BASED ALLOY COMPOSITIONS AND PRODUCTS FORMED THEREFROM
A ternary alloy wherein copper, manganese, and a ternary element are melted together and cast into an article and the article is subjected to an age-hardening treatment. A process for producing an age-hardened copper-manganese-nickel alloy, the process including melting a composition comprising copper, manganese and nickel; pouring the molten composition comprising copper, manganese, and nickel to form a casting with a composition comprising copper, manganese, and nickel, and aging the casting so produced. An article containing copper, manganese, and a ternary element, in a cast form and the cast form has subsequently undergone age-hardening treatment. A ternary alloy comprising copper, manganese, and a ternary element melted together and solidified into a casting, wherein the microstructure of the casting produced shows substantially low microporosity attributable to dendritic solidification.
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The present U.S. patent application is related to and claims the priority benefit of U.S. Provisional Patent Application Ser. No. 62/062,518, filed Oct. 10, 2014, the contents of which are hereby incorporated by reference in their entirety into the present disclosure. Further, this application is related to co-pending U.S. patent application Ser. No. 13/441,611, filed Apr. 6, 2012, the contents of which are incorporated by herein by reference in their entirety.
TECHNICAL FIELDThis disclosure relates to metals and alloys suitable for use in the production of castings and potential other forms (for example rolling, forging, drawing etc.) for use in various industrial applications, such as, but not limited to plumbing and valve fittings.
BACKGROUNDThis section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
The present invention generally relates to copper-based alloys that are suitable for use in the production of castings (for example, plumbing castings), wrought forms (for example, produced by rolling, drawing, forging, etc.), and potentially other forms. The invention also relates to the production and processing of such alloys, and particularly processes that are capable of enhancing the mechanical properties of such alloys.
Alloys based on Cu and Mn in wrought form are well known for special characteristics, such as mechanical damping capacity, resiliency and magnetic behavior. With the exception of these specialty alloys, Mn is usually a minor alloying element in Cu. The most common example is the high-strength yellow brasses, also known as manganese bronzes, which typically contain only about 2 weight percent Mn.
Cu—Mn alloy compositions that undergo cellular and dendritic growth during directional solidification as a result of their compositions containing manganese contents that are intentionally above or below the congruent point or minimum in the liquidus/solidus of the Cu—Mn phase diagram, shown in
Copper-manganese alloys having relatively large amounts of manganese have conventionally been produced in wrought form, for example, products in the form of wires, thin plates/sheets, rods, foils, etc. Microporosity is not a concern in such products as they may be hot- and/or cold-worked to remove the microporosity, unlike cast products. However, it is desirable if methods were available for casting copper-manganese alloys that were free of microporosity and dendritic growth. Compositions that lend themselves to eliminating or reducing microporosity and dendritic growth have been described in U.S. patent application Ser. No. 13/441,611 (Publication No. US2013/0094989 A1), the contents of which are incorporated by reference herein in their entirety.
For many applications, including but not limited to plumbing and valve fittings, it is desirable to procure the objects in cast form of Cu—Mn alloys. It is further desirable and advantageous if the strength and other mechanical properties of such cast Cu—Mn alloys can be further controlled and enhanced through compositional changes and/or heat treatments. Due to the very narrow freezing range of alloys near the Cu—Mn congruent point, cellular solidification occurs instead of the common dendritic morphology found in most cast alloys. The cellular growth morphology leads to a microporosity-free structure. Even though the alloy was initially developed as an alternative to leaded casting bronzes for piping and plumbing, its lack of porosity shows potential for more demanding structural applications where fatigue is a primary concern. While the as-cast strength was found to be higher than that of comparable cast brasses and bronzes, it is still not high enough for these applications where stronger alloys like stainless steel are the primary choices.
Thus there is unmet need for cast Cu—Mn alloys that have higher strength than currently available for use in demanding structural applications where high mechanical strength and fatigue resistance are desired.
SUMMARYA ternary alloy is disclosed. The ternary alloy comprises copper, manganese, and a ternary element, wherein copper, manganese, and the ternary element are capable of being melted together and cast into an article and the article is subjected to an age-hardening treatment.
A process for producing an age-hardened copper-manganese-nickel alloys is disclosed. The process includes melting a composition comprising copper, manganese and nickel; pouring the molten composition comprising copper, manganese, and nickel to form a casting with a composition comprising copper, manganese, and nickel; and aging the casting produced at a temperature in the range of 300° C. to 600° C. for a time period.
An article made of an alloy is disclosed. The article contains copper, manganese, and a ternary element, wherein copper, manganese and the ternary element are in a cast form and the cast form has subsequently undergone age-hardening treatment and contains a precipitated phase.
A ternary alloy containing copper, manganese and a ternary element is disclosed. The alloy includes copper, manganese, and a ternary element melted together and solidified into a casting, wherein the microstructure of the solidified casting produced exhibits substantially low microporosity attributable to dendritic solidification.
While some of the figures shown herein may have been generated from scaled drawings or from photographs that are scalable, it is understood that such relative scaling within a figure are by way of example, and are not to be construed as limiting.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.
As mentioned in the Back-ground section, the goal of this disclosure is to increase the strength of Cu—Mn alloys. It is also important that the freezing range be kept minimal so that the benefits of the cellular structure found in the near-congruent Cu—Mn alloy are not all sacrificed. In this disclosure, a primary strengthening approach adopted is utilization of ternary alloying elements, in particular, Nickel (Ni). Although Ni has a small solid solution strengthening effect, previous studies showed that additions of Ni can make alloys that are precipitation-hardenable through the formation of the NiMn phase or α(Mn) phase.
The Cu—Ni binary system is well known to be an isomorphous system and the Ni—Mn system displays a congruent minimum in the liquidus-solidus very similar to that of the Cu—Mn system. While work on the Cu—Mn—Ni ternary liquidus temperature surface is rather limited, it suggests a trough in the liquidus that runs from the Ni—Mn congruent point (60 wt pct Mn, 1020° C.) to the Cu—Mn congruent point (35 wt pct Mn, 873° C., as shown in
In this disclosure we use the term ternary element to mean a metallic element added to a Cu—Mn binary alloy. Thus nickel is an example of a ternary element of this disclosure. Further, the term “about” may be used in describing the weight percent of an element or a constituent of a ternary alloy or a binary alloy. For example the phrase “about 35 weight percent” means 35 weight percent with in a tolerance of +/−1 percent. When a constituent is about 1 percent, however, it must be understood, that zero weight percent is not included.
In experiments leading to this disclosure, alloys were prepared by melting in an open-air induction furnace in approximately 1-kg charges of the compositions (in weight percent, sometimes abbreviated as wt. percent or wt. % or wt pct) listed in
Samples for optical microscopy of the alloys made as described above were sectioned by an abrasive saw, then ground on silicon carbide paper from 320 to 600 grit. Polishing was done with 6- and 9-μm diamond paste with the final polish being done with a 0.05 μm alumina slurry on napped cloths. To evaluate the solidification structure a micro etchant containing 25 g iron (III) chloride, 25 ml concentrated hydrochloric acid and 100 ml deionized water was used to reveal the morphology. Evaluation of the microstructure was done through the use of optical microscopy and scanning electron microscopy (SEM). The SEM used was an FEI® XL40 SEM with an acceleration voltage of 15 keV. Evaluation of the composition was done through Energy Dispersive X-ray Spectroscopy (EDS) in an SEM using a thin window detector (EDAX® ESEM 2020). Measurements were done using an accelerating voltage of 15 keV with an area analysis to evaluate the overall composition. Analysis was done through the EDAX program with standardless EDS through the use of the calibrated Standard Element Coefficients (SEC). X-Ray diffraction (XRD) was performed on the ingots using a Bruker® D-8 diffractometer with a copper source at a scan rate of 8 deg/min with measurements taken at increments of 0.02 deg from 2θ between 20 to 90 deg.
Alloy compositions made as described above were subjected to aging treatments in a box furnace in air at 723 K (450° C.) for 1, 10, 20, 50 and 100 h. The temperature was measured/monitored through the use of a K-type thermocouple attached to an Omega® HH806AU reader. Temperature was observed to fluctuate by less than 15° C. during the aging process. The specimens were ˜1 cm thick slices cut transversely from the as-cast slugs. After aging these samples were prepared for metallography by the same technique as described above. Vickers hardness testing was conducted using a LECO®, LV-100 hardness testing apparatus. Each sample was tested 5 times with a load of 30 kgf.
It is to be recognized that the alloys were aged directly in the as-cast condition. As inferred from the Cu—Mn binary phase diagram and metallographic observations, the alloys α solidify to a single solid phase. In the Cu—Mn binary system, precipitation below the α(Mn) solvus temperature is known to be so sluggish that solution treatment prior to aging is not necessary. Hence we do not need to solution treat (namely, as in typical solution treatments, reheating from room temperature to a temperature higher than solvus temperature, hold and then quickly cool to room temperature). Such solution treatment is a normal step in age-hardening processes. But in the experiments leading to this disclosure no solution treatment was given to the alloys in the age-hardening treatments of this disclosure. A special feature of these alloys that we can age the cast structure directly without solution treatment, which is an advantage. However one can design age-hardening processes for the alloys of this disclosure that can include a solution treatment at a temperature higher than the solvus temperature. Thus the age-hardening process of this disclosure can include a solution treatment step. If a solution treatment is used in the Cu—Mn—Ni system, it can be done in the temperature range of 700-850° C. Solution treatment step, when employed, precedes the aging step in a typical age-hardening process.
The results of EDS analysis have shown little loss of the alloying elements during melting, except for the first heat of the 5 wt pct Ni alloy which had a nickel content measuring closer to 2 wt pct Ni. The full composition is shown in
Compared to the Cu—Mn binary it appears that the freezing range for all these ternary alloys is too large for complete cellular solidification in conventional casting. It should be noted that during this study, however, even in the alloys with little to no cellular solidification (i.e., mostly or completely dendritic), the presence of microshrinkage porosity was not observed. This is unquestionably beneficial to as-cast mechanical properties, especially for fatigue resistance. Potentially, altering the casting parameters, such as increasing the superheat, may promote the desired solidification morphology. But since no microporosity was observed during this study, which was the goal for the as-cast structures, the freezing ranges appear to be sufficiently narrow to hinder fluid flow defects, even without the formation of a completely cellular (non-dendritic) structure.
The hardness of alloys as-cast is listed in Table I below (In Table 1, in the alloy designations represent weight percent of the corresponding element.)
From Table I, it can be seen that the increase in Ni and Mn in these alloys from the Cu—Mn congruent composition (Cu-35 wt pct Mn) does increase the hardness (strength) by up to ˜20%, through solid solution strengthening alone, when compared to the congruent Cu—Mn binary alloy.
To evaluate the aged microstructure, the 2 wt pct Ni alloy was etched and evaluated through SEM and optical microscopy.
Through XRD analysis, the formation of α(Mn) after aging was confirmed by comparing the as-cast spectra to the spectra of samples aged for 100 h at 450° C.
Homogenization may lead to an increase in strength with the whole microstructure being aged or it may move the composition away from a hardenable composition all together. Manipulation of the as-cast structure and the microsegregation present may be a way to get age-hardenable alloys that have average compositions outside of the hardenable region and closer to the narrow freezing range trough in the Cu—Mn—Ni system to minimize the freezing range and promote a more cellular or less dendritic structure. It is also important to note that the freezing range, although not narrow enough for completely cellular growth, was not wide enough to yield shrinkage porosity in any of the Cu—Mn—Ni alloys of this disclosure, which is the primary benefit of the near-congruent Cu—Mn alloys. That is, the onset of microporosity formation occurs at a wider freezing range than the onset of transition from cellular to dendritic solidification. Therefore if the criterion for selecting alloy compositions is to obtain a defect free structure, instead of a cellular structure, there is increased freedom for creating an alloy with a better aging response.
As mentioned previously, a solution treatment step that also serves as homogenizing treatment step can be set up. The terms homogenization and solution treatment are sometimes used synonymously. Such a homogenization/solution treatment step before aging is most generally conducted between the solvus and the solidus (which depend on composition). The temperature range for such a step before aging can be 700-850° C. for alloys of this disclosure, depending on the composition.
In this disclosure, the effect of Ni on the mechanical properties was evaluated in parallel with the resulting cast morphology to gauge Ni as a potential ternary alloying addition to increase the strength without sacrificing the benefits of the cast morphology found in the near-congruent Cu—Mn binary alloys. Evaluation of the as-cast morphology showed varying degree of cellular solidification, with the 2 weight percent Ni alloy showing the least and the 5 weight percent alloy the most, 1% and 80% cellular morphology, respectively. Even though the amount of cellular solidification varied from alloy to alloy, no microshrinkage porosity was observed in any of the Cu—Mn—Ni alloys of this study. As for the aging response, the 2 weight percent Ni alloy was shown to increase the hardness by more than 100 percent after 100 h aging heat treatment through the precipitation of α(Mn) phase in the intradendritic regions. Aging responses in the other alloys showed very little hardness increase with aging treatment. Important factors were identified that could optimize the aging response of these alloys including evaluation of the effect of the as-cast microstructure on aging response and possible compositions that can be conventionally cast free of microshrinkage porosity.
As described above, precipitation-hardenable casting alloys have been demonstrated in the Cu—Mn—Ni ternary system, along a line of compositions between the congruent points in the Cu—Mn and Ni—Mn binary systems. As mentioned earlier, this disclosure is related to U.S. patent application Ser. No. 13/441,611, filed Apr. 6, 2012 which covers near-congruent Cu—Mn alloys. The Ni—Mn system also has a congruent freezing point (minimum) and the available thermodynamic data indicate that the Cu—Mn—Ni ternary system exhibits a trough of narrow freezing range compositions between the two binary congruent points, making these ideal compositions for castability, as taught in the above applications for the Cu—Mn system. In this disclosure, compositions near the narrow freezing range trough in the Cu—Mn—Ni system with up to 25 wt pct Ni were utilized to take advantage of the narrow freezing range for high castability.
The above description has established that addition of nickel followed by age-hardening is a viable technique to increase hardness of the ternary Cu—Mn—Ni alloy. It is well known to those skilled in the art that increased hardness implies increased mechanical strength. It is further known that a strong correlation exists between mechanical strength and fatigue strength. The higher the mechanical strength of a metal or alloy is, the higher is its fatigue strength. Thus the principles and methods of this disclosure clearly teach techniques to increase the fatigue resistance of Cu—Mn alloys by ternary additions such as, but not limited to, nickel.
Based on the above description, we can define a ternary alloy comprising copper, manganese and a ternary element wherein copper, manganese, and the ternary element are melted together and cast into an article and the article is subjected to an age-hardening treatment. In particular, the ternary element can be nickel. Other non-limiting examples of the ternary element include cobalt, chromium, iron and zinc. In employing nickel, it is clear from the above-described studies that nickel content can vary in a non-limiting range of 1-25 weight percent. Further, it can be inferred from the studies described above, that Cu—Mn—Ni alloys can be made advantageously such that weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55. These compositions are indicated as a parallelogram designated as 401 in
It is further clear that based on the studies conducted, a process for producing an age-hardened copper-manganese-nickel alloy can be described. The process included melting a composition comprising copper, manganese and nickel; pouring the molten composition comprising copper, manganese, and nickel to form a casting with a composition comprising copper, manganese, and nickel; and aging the casting at a temperature in the range of 300° C. to 600° C. The aging period in this process can vary from 1 h to 100 h and the nickel content can vary from 1 to 25 weight percent. Further, alloys that lend themselves to this process include Cu—Mn—Ni alloys which have weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55. These compositions are indicated as within the parallelogram designated as 401 in
Based on the above descriptions, articles or products for various applications, such as plumbing as a non-limiting example, can be made using the method of forming a melt comprising copper, introducing manganese into the melt, and adding other elements or metals, casting the alloy in a mold to form the article. The cast-alloy can then be subjected to age-hardening processes as described in this disclosure. In a preferred embodiment, the element added is nickel. Instead of introducing manganese into the melt, metals (Cu, Mn) and/or any other elements or metallic additives can be melted together. In particular, an article, such as but not limited to a plumbing valve or fitting can be made from an alloy comprising copper; manganese; and a ternary element, wherein copper, manganese and the ternary element are in a cast form and the cast form has subsequently undergone age-hardening treatment. In particular, the ternary element can be nickel in the range of 1-25 weight percent. Further it is advantageous to have the composition of the Cu—Mn—Ni alloy of such an article be such that weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55. These compositions are indicated as within the parallelogram designated as 401 in
It is also an objective of this description to disclose ternary alloys comprising copper, manganese, and a ternary element melted and solidified into a casting, wherein the microstructure of the solidified casting shows substantially low microporosity attributable to dendritic growth. In this disclosure, microporosity has the usual meaning of interdendritic porosity on the size scale of the dendrite arms or smaller, that results from insufficient liquid flow to feed solidification shrinkage; and by low microporosity, we mean microporosity less than about 1%. by volume. It is advantageous to use nickel as the ternary element. Further, in order to achieve the benefits of cellular solidification with much reduced dendritic growth, preferred embodiments include copper-manganese-nickel compositions with weight percent of nickel in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55. These compositions are indicated as within a parallelogram designated as 401 in
In the Cu—Mn—Ni alloys and composition, process and article embodiments described above, that include an aging treatment, and the aging treatment can be optionally preceded by a solution treatment at a temperature in the range of 700-850° C.
It is to be recognized that compositions falling into the region 401 of the ternary composition diagram of
The articles or products that can be produced for various applications, such as plumbing as a non-limiting example, can be made using a method of: forming a melt comprising copper, introducing manganese into the melt, adding other elements or metals into the melt, and melting copper, manganese and added elements to form an alloy, and casting the resulting alloy into a mold to form the article, wherein the carbon and oxygen contents of the alloy are controlled in order to control the formation of graphite, manganese carbide, and/or manganese particles within the article. Methods of controlling the copper and oxygen contents during the melting process of such alloys are described in U.S. patent application Ser. No. 13/441,611 (Publication No. US 2013/0094989 A1), the contents of which are incorporated by reference herein in their entirety.
The cast-alloy can then be subjected to age-hardening processes as described in this disclosure. In a preferred embodiment, the element added is nickel. It should be noted that in melting the alloy for making the casting, the metals, copper and manganese and nickel can also be melted together. Further nickel can be added to molten copper before manganese is added. Nickel can also be introduced into the Cu—Mn melt. Those skilled in the art will be able to infer many other ways of achieving the desired composition for the melt before pouring into the mold for making the casting.
It should be recognized that ternary elements other than nickel can be used as the ternary element in alloys of this disclosure. Examples of such ternary elements include, but are not limited to, cobalt, zinc, chromium, and iron. It is possible to add more than one of the elements from this non-limiting group of nickel, cobalt, zinc, chromium, and iron to a copper-manganese binary system and apply the principles and methods of this disclosure. Thus it is an objective of this disclosure to teach that by employing methods and principles of this disclosure it is possible to have 4-component, 5-component systems or in general terms multi-component systems. In accordance with the principles of this disclosure these systems can be narrow freezing range and/or age-hardenable. Thus those skilled in the art will recognize that the teachings of this disclosure are not limited to binary and ternary alloy systems.
While this disclosure describes several compositions, it is to be understood that other additives are possible. While specific age-hardening treatments are described in detail in terms of time and temperature, other combinations will be apparent to those skilled in the art. This disclosure is intended to cover all compositions described, methods described, age-hardening treatments and methods of making articles using the processes described here. It is also possible to apply age-hardening treatments described here to articles made of alloys with compositions described here that have been already cast into articles.
While the present disclosure has been described with reference to certain embodiments, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible that are within the scope of the present disclosure without departing from the spirit and scope of the present disclosure. For example, other similar compositions and variation of the aging treatment disclosed in this disclosure can be adapted by those skilled in the art. Addition of other elements and/or metals or combinations of elements or metals to achieve desired microstructures can be inferred by others skilled in the art. Further, additions of other elements or metals, or combinations of elements or metals, to enhance mechanical properties by suitable aging treatments are also possible and can be derived from this disclosure. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. Thus, this disclosure is limited only by the following claims.
Claims
1. A ternary alloy comprising: wherein copper, manganese, and the ternary element are melted together and cast into an article and the article is subjected to an age-hardening treatment.
- copper;
- manganese; and
- a ternary element,
2. The ternary alloy of claim 1, the ternary element is nickel.
3. The ternary alloy of claim 2, weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55.
4. The ternary alloy of claim 3, the age-hardening in the range of 300° C. to 600° C. for a time period.
5. The ternary alloy of claim 4, wherein the time period is in the range of 1 hour to 100 hours.
6. A process for producing an age-hardened copper-manganese-nickel alloy comprising:
- melting a composition comprising copper, manganese and nickel;
- pouring the molten composition comprising copper, manganese, and nickel to form a casting with a composition comprising copper, manganese, and nickel; and
- aging the casting produced at a temperature in the range of 300° C. to 600° C. for a time period.
7. The process of claim 6, wherein the time period is in the range of 1 hour to 100 hours.
8. The process of claim 6, weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55.
9. The process of claim 8, wherein the time period is in the range of 1 and 100 hours.
10. An article comprising:
- copper;
- manganese; and
- a ternary element,
- wherein copper, manganese and the ternary element are in a cast form and the cast form has subsequently undergone age-hardening treatment and contains a precipitated phase.
11. The article of claim 10, the ternary element is nickel.
12. The article of claim 11, weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55.
13. The article of claim 12, the age-hardening treatment includes aging in the temperature range of 300° C. to 600° C. for a time period in the range of 1 hour to 100 hours.
14. The article of claim 11, the article is a plumbing valve or fitting.
15. The article of claim 12, the article is a plumbing valve or fitting.
16. The article of claim 13, the article is a plumbing valve or fitting.
17. A ternary alloy comprising copper, manganese, and a ternary element melted together and solidified into a casting, wherein the microstructure of the casting produced exhibits substantially low microporosity attributable to dendritic solidification.
18. The ternary alloy of claim 17, the ternary element is nickel.
19. The ternary alloy of claim 18, weight percent of nickel is in the range of about 1 to about 25 and the weight percent of manganese is in the range of about 35 to about 55.
20. The ternary alloy of claim 1, the ternary element is one of cobalt, zinc, chromium, and iron.
21. The article of claim 10, the ternary the ternary element is one of cobalt, zinc, chromium, and iron.
22. The ternary alloy of claim 17, the ternary element is one of cobalt, zinc, chromium, and iron.
23. The ternary alloy of claim 1, wherein the age-hardening treatment is preceded by a solution treatment.
24. The process of claim 10, wherein the aging of the casting is preceded by a solution treatment.
25. The ternary alloy of claim 23, wherein the solution treatment temperature is in the range of 700° C. to 850° C.
26. The process of claim 24, wherein the solution treatment temperature is in the range of 700° C. to 850° C.
Type: Application
Filed: Oct 10, 2015
Publication Date: Apr 14, 2016
Applicant: PURDUE RESEARCH FOUNDATION (West Lafayette, IN)
Inventors: Kevin Paul Trumble (West Lafayette, IN), Kevin Joseph Chaput (Merritt Island, FL)
Application Number: 14/880,217