EP3475456B1

EP3475456B1 - High-strength, corrosion resistant aluminum alloys for use as fin stock and methods of making the same

Info

Publication number: EP3475456B1
Application number: EP17711493.1A
Authority: EP
Inventors: Jyothi Kadali; Eider Alberto SIMIELLI
Original assignee: Novelis Inc Canada; Novelis Inc
Current assignee: Novelis Inc Canada; Novelis Inc
Priority date: 2017-03-03
Filing date: 2017-03-03
Publication date: 2020-01-08
Anticipated expiration: 2037-03-03
Also published as: AU2017305004B2; CA2990212A1; WO2018160189A1; RU2681090C1; AU2017305004A1; CN109312431A; JP6639635B2; BR112017028464A2; ES2772729T3; JP2019512592A; EP3475456A1; MX2017017133A; KR101904704B1; CN109312431B; CA2990212C; BR112017028464B1

Description

FIELD

This disclosure relates to the fields of material science, material chemistry, metallurgy, aluminum alloys, aluminum fabrication, and related fields. More specifically, the disclosure provides novel aluminum alloys that can be used in a variety of applications, including, for example, as a fin stock for a heat exchanger.

BACKGROUND

Heat exchangers are widely used in various applications, including, but not limited to, heating and cooling systems in various industrial and chemical processes. Many of these configurations utilize fins in thermally conductive contact with the outside of tubes to provide increased surface area across which heat can be transferred between the fluids. In addition, fins are used to regulate flow of fluids through the heat exchanger. However, aluminum alloy heat exchangers have a relatively high susceptibility to corrosion. Corrosion eventually leads to loss of refrigerant from the tubes and failure of the heating or cooling system. High strength, corrosion resistant alloys are desirable for improved product performance. However, identifying alloy compositions and processing conditions that will provide such an alloy that addresses these failures has proven to be a challenge.
Heat exchanger tubes can be made from copper or an aluminum alloy and heat exchanger fins can be made from a different aluminum alloy (e.g., AA1100 or AA7072). The fins can be fitted over copper or aluminum tubes and mechanically assembled. Larger heating, ventilation, air conditioning and refrigeration (HVAC&R) units can require longer fins and it is important they have sufficient strength for downstream processing (e.g., handling and/or forming into coils). One method to maintain strength of the fins is to provide thicker gauge fins; however, this can increase cost and add weight.
WO 2015/173984 A1 describes an aluminum alloy fin material for heat exchanger containing, in mass%, Si: 0.6-1.6%, Fe: 0.5-1.2%, Mn: 1.2-2.6%, Zn: 0.4-3.0% and Cu: less than 0.2% with the remainder being Al and unavoidable impurities.

SUMMARY

Covered embodiments of the invention are defined by the claims, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below.
Provided herein are novel aluminum alloys that exhibit high strength and corrosion resistance. The aluminum alloys described herein comprise 0.7 - 3.0 wt. % Zn, 0.15 - 0.35 wt. % Si, 0.25 - 0.65 wt. % Fe, 0.05 - 0.20 wt. % Cu, 0.75 - 1.50 wt. % Mn, 0.50 - 1.50 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al. In one embodiment, the aluminum alloy comprises 1.0 - 2.5 wt. % Zn, 0.2 - 0.35 wt. % Si, 0.35 - 0.60 wt. % Fe, 0.10 - 0.20 wt. % Cu, 0.75 - 1.25 wt. % Mn, 0.90 - 1.30 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al. In another embodiment, the aluminum alloy comprises 1.5 - 2.5 wt. % Zn, 0.17 - 0.33 wt. % Si, 0.30 - 0.55 wt. % Fe, 0.15 - 0.20 wt. % Cu, 0.80 - 1.00 wt. % Mn, 1.00 - 1.25 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al. Optionally, the aluminum alloy comprises 0.9 - 2.6 wt. % Zn, 0.2 - 0.33 wt. % Si, 0.49 - 0.6 wt. % Fe, 0.15 - 0.19 wt. % Cu, 0.79 - 0.94 wt. % Mn, 1.13 - 1.27 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al. Optionally, the aluminum alloy comprises 1.4 - 1.6 wt. % Zn, 0.2 - 0.33 wt. % Si, 0.49 - 0.6 wt. % Fe, 0.15 - 0.19 wt. % Cu, 0.79 - 0.94 wt. % Mn, 1.13 - 1.27 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al. The alloy can be produced by casting (e.g., direct chill casting or continuous casting), homogenization, hot rolling, cold rolling, and/or annealing. The alloy can be in an H temper or an O temper.
The yield strength of the alloy is at least 70 MPa. The ultimate tensile strength of the alloy can be at least 170 MPa. The aluminum alloy can comprise an electrical conductivity above 37% based on the international annealed copper standard (IACS).
Optionally, the aluminum alloy comprises a corrosion potential of from 740 mV to -850 mV.
Also provided herein are products comprising the aluminum alloy as described herein. The products can include a fin stock. Optionally, the gauge of the fin stock is 1.0 mm or less (e.g., 0.15 mm or less). Further provided herein are articles comprising a tube and a fin, wherein the fin comprises the fin stock as described herein.
Further provided herein are methods of producing a metal product. The methods include the steps of casting an aluminum alloy as described herein to form a cast aluminum alloy, homogenizing the cast aluminum alloy, hot rolling the cast aluminum alloy to produce a rolled product, and cold rolling the rolled product to a final gauge product. Optionally, the methods further include a step of annealing the final gauge product. Products (e.g., heat exchanger fins) obtained according to the methods are also provided herein.
Further aspects, objects, and advantages will become apparent upon consideration of the detailed description of non-limiting examples that follow.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 contains digital images of exemplary alloys described herein coupled with a comparative alloy described herein and subjected to corrosion testing for various time periods.
Figure 2 contains digital images of exemplary alloys described herein coupled with a comparative alloy described herein and subjected to corrosion testing for various time periods.

DETAILED DESCRIPTION

Described herein are high-strength, corrosion resistant aluminum alloys and methods of making and processing the same. The aluminum alloys described herein exhibit improved mechanical strength, corrosion resistance, and/or formability. The alloys provided herein include a zinc constituent and can be especially useful as a sacrificial alloy (e.g., as fin stock material for use in combination with copper or aluminum alloy tubes in heat exchangers). The disclosed alloy composition provides a material having mechanical strength as well as sacrificial alloy characteristics. The alloy material can be formed as fin stock and attached mechanically to copper or aluminum alloy tubing. The fin stock can sacrificially corrode, thus protecting the copper or aluminum alloy tubing from corrosion. Additionally, the aluminum alloy fin stock described herein has excellent mechanical strength providing thinner gauge aluminum alloy fin stock. The alloys can be used as fin stock in industrial applications, including in heat exchangers, or in other applications. In a heat exchanger, the alloys serve as a sacrificial component, ensuring the protection of other components of the heat exchanger (e.g., a tube to which the alloy is attached).

Definitions and Descriptions:

The terms "invention," "the invention," "this invention," and "the present invention" used herein are intended to refer broadly to all of the subject matter of this patent application and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below.
In this description, reference is made to alloys identified by aluminum industry designations, such as "series" or "1xxx." For an understanding of the number designation system most commonly used in naming and identifying aluminum and its alloys, see "International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys" or "Registration Record of Aluminum Association Alloy Designations and Chemical Compositions Limits for Aluminum Alloys in the Form of Castings and Ingot," both published by The Aluminum Association.
As used herein, the meaning of "a," "an," or "the" includes singular and plural references unless the context clearly dictates otherwise.
As used herein, a plate generally has a thickness of greater than 15 mm. For example, a plate may refer to an aluminum product having a thickness of greater than 15 mm, greater than 20 mm, greater than 25 mm, greater than 30 mm, greater than 35 mm, greater than 40 mm, greater than 45 mm, greater than 50 mm, or greater than 100 mm.
As used herein, a shate (also referred to as a sheet plate) generally has a thickness of from 4 mm to 15 mm. For example, a shate may have a thickness of 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, or 15 mm.
As used herein, a sheet generally refers to an aluminum product having a thickness of less than 4 mm. For example, a sheet may have a thickness of less than 4 mm, less than 3 mm, less than 2 mm, less than 1 mm, less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm.
Reference is made in this application to alloy temper or condition. For an understanding of the alloy temper descriptions most commonly used, see "American National Standards (ANSI) H35 on Alloy and Temper Designation Systems." An F condition or temper refers to an aluminum alloy as fabricated. An O condition or temper refers to an aluminum alloy after annealing. An Hxx condition or temper, also referred to herein as an H temper, refers to an aluminum alloy after cold rolling with or without thermal treatment (e.g., annealing). Suitable H tempers include HX1, HX2, HX3 HX4, HX5, HX6, HX7, HX8, or HX9 tempers. For example, the aluminum alloy can be cold rolled only to result in a possible H19 temper. In a further example, the aluminum alloy can be cold rolled and annealed to result in a possible H23 temper.
The following aluminum alloys are described in terms of their elemental composition in weight percentage (wt. %) based on the total weight of the alloy. For each alloy, the remainder is aluminum, with a maximum wt. % of 0.15 % for the sum of the impurities.
As used herein, "electrochemical potential" refers to a material's amenability to a redox reaction. Electrochemical potential can be employed to evaluate resistance to corrosion of aluminum alloys described herein. A negative value can describe a material that is easier to oxidize (e.g., lose electrons or increase in oxidation state) when compared to a material with a positive electrochemical potential. A positive value can describe a material that is easier to reduce (e.g., gain electrons or decrease in oxidation state) when compared to a material with a negative electrochemical potential. Electrochemical potential, as used herein, is a vector quantity expressing magnitude and direction.
As used herein, the meaning of "room temperature" can include a temperature of from 15 °C to 30 °C, for example 15 °C, 16 °C, 17 °C, 18 °C, 19 °C, 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C, or 30 °C. All ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a stated range of "1 to 10" should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges beginning with a minimum value of 1 or more, e.g., 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to 10.

Alloy Compositions

Described below are novel aluminum alloys. In certain aspects, the alloys exhibit high strength, corrosion resistance, and/or high formability. The properties of the alloys are achieved due to the elemental compositions of the alloys as well as the methods of processing the alloys to produce the described sheets, plates, and shates. Specifically, increased zinc (Zn) content provides alloys that preferentially corrode when attached to copper or other aluminum alloy tubes, thus providing cathodic protection to the tubes. Surprisingly, Zn addition has exhibited additional solute strengthening in addition to the strengthening effect of increased magnesium (Mg) content. Additionally, an optimum Zn content has been observed. In some examples, additions of Zn of greater than 2.0 wt. % are not desirable, as such amounts can have a detrimental effect on conductivity and self-corrosion rates. However, in some examples, it may be desirable to sacrifice those conductivity and corrosive properties to allow for sufficient cathodic protection of the tube. To this end, a maximum Zn content of up to 3.0 wt. % can be used to provide the desired corrosion, conductivity, and strength properties.
The alloys and methods described herein can be used in industrial applications including sacrificial parts, heat dissipation, packaging, and building materials. The alloys described herein can be employed as industrial fin stock for heat exchangers. The industrial fin stock can be provided such that it is more resistant to corrosion than currently employed industrial fin stock alloys (e.g., AA7072 and AA1100) and will still preferentially corrode, protecting other metal parts incorporated in a heat exchanger.

The alloys have the following elemental composition as provided in Table 1.

Table 1

Element	Weight Percentage (wt. %)
Zn	0.7 - 3.0
Si	0.15 - 0.35
Fe	0.25 - 0.65
Cu	0.05 - 0.20
Mn	0.75 - 1.50
Mg	0.50 - 1.50
Cr	0.00 - 0.10
Ti	0.00 - 0.10
Others	0 - 0.05 (each)
Others	0 - 0.15 (total)
Al	Remainder

In one embodiment, the alloys have the following elemental composition as provided in Table 2.

Table 2

Element	Weight Percentage (wt. %)
Zn	1.0 - 2.5
Si	0.2 - 0.35
Fe	0.35 - 0.60
Cu	0.10 - 0.20
Mn	0.75 - 1.25
Mg	0.90 - 1.30
Cr	0.00 - 0.05
Ti	0.00 - 0.05
Others	0 - 0.05 (each)
Others	0 - 0.15 (total)
Al	Remainder

In another embodiment, the alloys have the following elemental composition as provided in Table 3.

Table 3

Element	Weight Percentage (wt. %)
Zn	1.5 - 2.5
Si	0.17 - 0.33
Fe	0.30 - 0.55
Cu	0.15 - 0.20
Mn	0.80 - 1.00
Mg	1.00 - 1.25
Cr	0.00 - 0.05
Ti	0.00 - 0.05
Others	0 - 0.05 (each)
Others	0 - 0.15 (total)
Al	Remainder

In yet a further embodiment, the alloys have the following elemental composition as provided in Table 4.

Table 4

Element	Weight Percentage (wt. %)
Zn	0.9 - 2.6
Si	0.2 - 0.33
Fe	0.49 - 0.6
Cu	0.15 - 0.19
Mn	0.79 - 0.94
Mg	1.13 - 1.27
Cr	0.00 - 0.05
Ti	0.00 - 0.05
Others	0 - 0.05 (each)
Others	0 - 0.15 (total)
Al	Remainder

The alloy includes zinc (Zn) in an amount from 0.7 % to 3.0 % (e.g., from 1.0 % to 2.5 %, from 1.5 % to 3.0 %, from 0.9 % to 2.6 %, or from 1.4 % to 1.6 %) based on the total weight of the alloy. For example, the alloy can include 0.7 %, 0.71 %, 0.72 %, 0.73 %, 0.74 %, 0.75 %, 0.76 %, 0.77 %, 0.78 %, 0.79 %, 0.8 %, 0.81 %, 0.82 %, 0.83 %, 0.84 %, 0.85 %, 0.86 %, 0.87 %, 0.88 %, 0.89 %, 0.9 %, 0.91 %, 0.92 %, 0.93 %, 0.94 %, 0.95 %, 0.96 %, 0.97 %, 0.98 %, 0.99%, 1.0 %, 1.01 %, 1.02 %, 1.03 %, 1.04 %, 1.05 %, 1.06 %, 1.07 %, 1.08 %, 1.09 %, 1.1 %, 1.11 %, 1.12 %, 1.13 %, 1.14 %, 1.15 %, 1.16 %, 1.17 %, 1.18 %, 1.19 %, 1.2 %, 1.21 %, 1.22 %, 1.23 %, 1.24 %, 1.25 %, 1.26 %, 1.27 %, 1.28 %, 1.29 %, 1.3 %, 1.31 %, 1.32 %, 1.33 %, 1.34 %, 1.35 %, 1.36 %, 1.37 %, 1.38 %, 1.39 %, 1.4 %, 1.41 %, 1.42 %, 1.43 %, 1.44 %, 1.45 %, 1.46 %, 1.47 %, 1.48 %, 1.49 %, 1.5 %, 1.51 %, 1.52 %, 1.53 %, 1.54 %, 1.55 %, 1.56 %, 1.57 %, 1.58 %, 1.59 %, 1.6 %, 1.61 %, 1.62 %, 1.63 %, 1.64 %, 1.65 %, 1.66 %, 1.67 %, 1.68 %, 1.69 %, 1.7 %, 1.71 %, 1.72 %, 1.73 %, 1.74 %, 1.75 %, 1.76 %, 1.77 %, 1.78 %, 1.79 %, 1.8 %, 1.81 %, 1.82 %, 1.83 %, 1.84 %, 1.85 %, 1.86 %, 1.87 %, 1.88 %, 1.89 %, 1.9 %, 1.91 %, 1.92 %, 1.93 %, 1.94 %, 1.95 %, 1.96 %, 1.97 %, 1.98 %, 1.99 %, 2.0 %, 2.01 %, 2.02 %, 2.03 %, 2.04 %, 2.05 %, 2.06 %, 2.07 %, 2.08 %, 2.09 %, 2.1 %, 2.11 %, 2.12 %, 2.13 %, 2.14 %, 2.15 %, 2.16 %, 2.17 %, 2.18 %, 2.19 %, 2.2 %, 2.21 %, 2.22 %, 2.23 %, 2.24 %, 2.25 %, 2.26 %, 2.27 %, 2.28 %, 2.29 %, 2.3 %, 2.31 %, 2.32 %, 2.33 %, 2.34 %, 2.35 %, 2.36 %, 2.37 %, 2.38 %, 2.39 %, 2.4 %, 2.41 %, 2.42 %, 2.43 %, 2.44 %, 2.45 %, 2.46 %, 2.47 %, 2.48 %, 2.49 %, 2.5 %, 2.51 %, 2.52 %, 2.53 %, 2.54 %, 2.55 %, 2.56 %, 2.57 %, 2.58 %, 2.59 %, 2.6 %, 2.61 %, 2.62 %, 2.63 %, 2.64 %, 2.65 %, 2.66 %, 2.67 %, 2.68 %, 2.69 %, 2.7 %, 2.71 %, 2.72 %, 2.73 %, 2.74 %, 2.75 %, 2.76 %, 2.77 %, 2.78 %, 2.79 %, 2.8 %, 2.81 %, 2.82 %, 2.83 %, 2.84 %, 2.85 %, 2.86 %, 2.87 %, 2.88 %, 2.89 %, 2.9 %, 2.91 %, 2.92 %, 2.93 %, 2.94 %, 2.95 %, 2.96 %, 2.97 %, 2.98 %, 2.99 %, or 3.0 % Zn. All percentages are expressed in wt. %. The zinc content can improve the corrosion resistance of the aluminum alloys described herein. Specifically, when zinc is incorporated at a level as described herein, such as from 1.0 % to 2.6 %, the alloys exhibit enhanced corrosion resistance as compared to fin stock typically used in industrial processes (e.g., 1xxx series and 7xxx series alloys). In some further examples, Zn can decrease resistance to corrosion when incorporated at weight percentages exceeding those described herein. In still further examples, Zn can be incorporated in an aluminum alloy in an optimal amount, as described herein, to provide an alloy suitable for use as an industrial fin. For example, at Zn levels higher than those described herein, the alloys for use as fins can corrode more rapidly than for fins containing the described amount of Zn, resulting in perforations in the fin. As a result, the mechanical integrity and thermal performance of the heat exchanger can be compromised, thus affecting the service life of the heat exchanger.
The disclosed alloy includes silicon (Si) in an amount from 0.15 % to 0.35 % (e.g., from 0.20 % to 0.35 %, from 0.17 % to 0.33 %, or from 0.20 % to 0.33 %) based on the total weight of the alloy. For example, the alloy can include 0.15 %, 0.16 %, 0.17 %, 0.18 %, 0.19 %, 0.2 %, 0.21 %, 0.22 %, 0.23 %, 0.24 %, 0.25 %, 0.26 %, 0.27 %, 0.28 %, 0.29 %, 0.30 %, 0.31 %,0.32 %, 0.33 %, 0.34 %, or 0.35 % Si. All percentages are expressed in wt. %.
The alloy also includes iron (Fe) in an amount from 0.25 % to 0.65 % (e.g., from 0.35 % to 0.60 %, from 0.30 % to 0.55 %, or from 0.49 % to 0.6 %) based on the total weight of the alloy. For example, the alloy can include 0.25 %, 0.26 %, 0.27 %, 0.28 %, 0.29 %, 0.3 %, 0.31 %, 0.32 %, 0.33 %, 0.34 %, 0.35 %, 0.36 %, 0.37 %, 0.38 %, 0.39 %, 0.4 %, 0.41 %, 0.42 %, 0.43 %, 0.44 %, 0.45 %, 0.46 %, 0.47 %, 0.48 %, 0.49 %, 0.5 %, 0.51 %, 0.52 %, 0.53 %, 0.54 %, 0.55 %, 0.56 %, 0.57 %, 0.58 %, 0.59 %, 0.6 %, 0.61 %, 0.62 %, 0.63 %, 0.64 %, or 0.65 % Fe. All percentages are expressed in wt. %.
The disclosed alloy includes copper (Cu) in an amount from 0.05 % to 0.20 % (e.g., from 0.10 % to 0.20 %, from 0.15 % to 0.20 %, or from 0.15 % to 0.19 %) based on the total weight of the alloy. For example, the alloy can include 0.05 %, 0.06 %, 0.07 %, 0.08 %, 0.09 %, 0.1 %, 0.11 %, 0.12 %, 0.13 %, 0.14 %, 0.15 %, 0.16 %, 0.17 %, 0.18 %, 0.19 %, or 0.2 % Cu. All percentages are expressed in wt. %.
The alloy includes manganese (Mn) in an amount from 0.75 % to 1.5 % (e.g., from 0.75 % to 1.25 %, from 0.80 % to 1.00 %, or from 0.79 % to 0.94 %) based on the total weight of the alloy. For example, the alloy can include 0.75 %, 0.76 %, 0.77 %, 0.78 %, 0.79 %, 0.8 %, 0.81 %, 0.82 %, 0.83 %, 0.84 %, 0.85 %, 0.86 %, 0.87 %, 0.88 %, 0.89 %, 0.9 %, 0.91 %, 0.92 %, 0.93 %, 0.94 %, 0.95 %, 0.96 %, 0.97 %, 0.98 %, 0.99 %, 1.0 %, 1.01 %, 1.02 %, 1.03 %, 1.04 %, 1.05 %, 1.06 %, 1.07 %, 1.08 %, 1.09 %, 1.1 %, 1.11 %, 1.12 %, 1.13 %, 1.14 %, 1.15 %, 1.16 %, 1.17 %, 1.18 %, 1.19 %, 1.2 %, 1.21 %, 1.22 %, 1.23 %, 1.24 %, 1.25 %, 1.26 %, 1.27 %, 1.28 %, 1.29 %, 1.3 %, 1.31 %, 1.32 %, 1.33 %, 1.34 %, 1.35 %, 1.36 %, 1.37 %, 1.38 %, 1.39 %, 1.4 %, 1.41 %, 1.42 %, 1.43 %, 1.44 %, 1.45 %, 1.46 %, 1.47 %, 1.48 %, 1.49 %, or 1.5 % Mn. All percentages are expressed in wt. %.
The alloy includes magnesium (Mg) in an amount from 0.50 % to 1.50 % (e.g., from 0.90 % to 1.30 %, from 1.00 % to 1.25 %, or from 1.13 % to 1.27 %) based on the total weight of the alloy. For example, the alloy can include 0.5 %, 0.51 %, 0.52 %, 0.53 %, 0.54 %, 0.55 %, 0.56 %, 0.57 %, 0.58 %, 0.59 %, 0.6 %, 0.61 %, 0.62 %, 0.63 %, 0.64 %, 0.65 %, 0.66 %, 0.67 %, 0.68 %, 0.69 %, 0.7 %, 0.71 %, 0.72 %, 0.73 %, 0.74 %, 0.75 %, 0.76 %, 0.77 %, 0.78 %, 0.79 %, 0.8 %, 0.81 %, 0.82 %, 0.83 %, 0.84 %, 0.85 %, 0.86 %, 0.87 %, 0.88 %, 0.89 %, 0.9 %, 0.91 %, 0.92 %, 0.93 %, 0.94 %, 0.95 %, 0.96 %, 0.97 %, 0.98 %, 0.99 %, 1.0 %, 1.01 %, 1.02 %, 1.03 %, 1.04 %, 1.05 %, 1.06 %, 1.07 %, 1.08 %, 1.09 %, 1.1 %, 1.11 %, 1.12 %, 1.13 %, 1.14 %, 1.15 %, 1.16 %, 1.17 %, 1.18 %, 1.19 %, 1.2 %, 1.21 %, 1.22 %, 1.23 %, 1.24 %, 1.25 %, 1.26 %, 1.27 %, 1.28 %, 1.29 %, 1.3 %, 1.31 %, 1.32 %, 1.33 %, 1.34 %, 1.35 %, 1.36 %, 1.37 %, 1.38 %, 1.39 %, 1.4 %, 1.41 %, 1.42 %, 1.43 %, 1.44 %, 1.45 %, 1.46 %, 1.47 %, 1.48 %, 1.49 %, or 1.5 % Mg. All percentages are expressed in wt. %.
The alloy includes chromium (Cr) in an amount up to 0.10 % (e.g., from 0 % to 0.05 %, from 0.001 % to 0.04 %, or from 0.01 % to 0.03 %) based on the total weight of the alloy. For example, the alloy can include 0.001 %, 0.002 %, 0.003 %, 0.004 %, 0.005 %, 0.006 %, 0.007 %, 0.008 %, 0.009 %, 0.01 %, 0.02 %, 0.03 %, 0.04 %, 0.05 %, 0.06 %, 0.07 %, 0.08 %, 0.09 %, or 0.1 % Cr. In some cases, Cr is not present in the alloy (i.e., 0 %). All percentages are expressed in wt. %.
The alloy includes titanium (Ti) in an amount up to 0.10 % (e.g., from 0 % to 0.05 %, from 0.001 % to 0.04 %, or from 0.01 % to 0.03 %) based on the total weight of the alloy. For example, the alloy can include 0.001 %, 0.002 %, 0.003 %, 0.004 %, 0.005 %, 0.006 %, 0.007 %, 0.008 %, 0.009 %, 0.01 %, 0.02 %, 0.03 %, 0.04 %, 0.05 %, 0.06 %, 0.07 %, 0.08 %, 0.09 %, or 0.1 % Ti. In some cases, Ti is not present in the alloy (i.e., 0 %). All percentages are expressed in wt. %.
Optionally, the alloy compositions can further include other minor elements, sometimes referred to as impurities, in amounts of 0.05 % or below, 0.04 % or below, 0.03 % or below, 0.02 % or below, or 0.01 % or below each. These impurities may include, but are not limited to, Ga, V, Ni, Sc, Ag, B, Bi, Zr, Li, Pb, Sn, Ca, Hf, Sr, or combinations thereof.
Accordingly, Ga, V, Ni, Sc, Ag, B, Bi, Zr, Li, Pb, Sn, Ca, Hf, or Sr may be present in an alloy in amounts of 0.05 % or below, 0.04 % or below, 0.03 % or below, 0.02 % or below, or 0.01 % or below. The sum of all impurities does not exceed 0.15 % (e.g., 0.1 %). All percentages are expressed in wt. %. The remaining percentage of the alloy is aluminum.
In one embodiment, aluminum alloys as described herein include 0.9 - 2.6 % Zn (e.g., 1.4 - 1.6 % Zn), 0.2 - 0.33 % Si, 0.49 - 0.6 % Fe, 0.15 - 0.19 % Cu, 0.79 - 0.94 % Mn, 1.13 - 1.27 % Mg, up to 0.05 % Cr, up to 0.05 % Ti, and up to 0.15 % of impurities, with the remainder as Al. For example, an exemplary alloy includes 1.53 % Zn, 0.3 % Si, 0.51 % Fe, 0.17 % Cu, 0.87 % Mn, 1.21 % Mg, 0.001 % Cr, 0.016 % Ti, and up to 0.15 % total impurities, with the remainder as Al. In some examples, an exemplary alloy includes 1.00 % Zn, 0.29 % Si, 0.51 % Fe, 0.16 % Cu, 0.86 % Mn, 1.2 % Mg, 0.001 % Cr, 0.011 % Ti, and up to 0.15 % total impurities, with the remainder as Al. In some examples, an exemplary alloy includes 2.04 % Zn, 0.29 % Si, 0.51 % Fe, 0.17 % Cu, 0.87 % Mn, 1.21 % Mg, 0.001 % Cr, 0.015 % Ti, and up to 0.15 % total impurities, with the remainder as Al. In some examples, an exemplary alloy includes 2.54 % Zn, 0.29 % Si, 0.51 % Fe, 0.17 % Cu, 0.88 % Mn, 1.23 % Mg, 0.001 % Cr, 0.012 % Ti, and up to 0.15 % total impurities, with the remainder as Al.

Alloy Properties

The mechanical properties of the aluminum alloy can be controlled by various processing conditions depending on the desired use. The alloy can be produced (or provided) in an H temper (e.g., HX1, HX2, HX3 HX4, HX5, HX6, HX7, HX8, or HX9 tempers). As one example, the alloy can be produced (or provided) in the H19 temper. H19 temper refers to products that are cold rolled. As another example, the alloy can be produced (or provided) in the H23 temper. H23 temper refers to products that are cold rolled and partially annealed. As a further example, the alloy can be produced (or provided) in the O temper. O temper refers to products that are cold rolled and fully annealed.
In some non-limiting examples, the disclosed alloys have high strength in the H tempers (e.g., H19 temper and H23 temper) and high formability (i.e., bendability) in the O temper. In some non-limiting examples, the disclosed alloys have good corrosion resistance in the H tempers (e.g., H19 temper and H23 temper), and O temper compared to conventional 7xxx and 1xxx series aluminum alloys employed as industrial fin stock.
In certain aspects, the aluminum alloys can have a yield strength (YS) of at least 70 MPa. In non-limiting examples, the yield strength is at least 70 MPa, at least 80 MPa, at least 90 MPa, at least 100 MPa, at least 110 MPa, at least 120 MPa, at least 130 MPa, at least 140 MPa, at least 150 MPa, at least 160 MPa, at least 170 MPa, at least 180 MPa, at least 190 MPa, at least 200 MPa, at least 210 MPa, at least 220 MPa, at least 230 MPa, at least 240 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, at least 290 MPa, at least 300 MPa, at least 310 MPa, at least 320 MPa, at least 330 MPa, at least 340 MPa, at least 350 MPa, or anywhere in between. In some cases, the yield strength is from 70 MPa to 350 MPa. For example, the yield strength can be from 80 MPa to 340 MPa, from 90 MPa to 320 MPa, from 100 MPa to 300 MPa, from 180 MPa to 300 MPa, or from 200 MPa to 300 MPa.
The yield strength will vary based on the tempers of the alloys. In some examples, the alloys described herein provided in an O temper can have a yield strength of from at least 70 MPa to 200 MPa. In non-limiting examples, the yield strength of the alloys in O temper is at least 70 MPa, at least 80 MPa, at least 90 MPa, at least 100 MPa, at least 110 MPa, at least 120 MPa, at least 130 MPa, at least 140 MPa, at least 150 MPa, at least 160 MPa, at least 170 MPa, at least 180 MPa, at least 190 MPa, at least 200 MPa, or anywhere in between.
In some further examples, the alloys described herein in an H temper can have a yield strength of at least 200 MPa, at least 210 MPa, at least 220 MPa, at least 230 MPa, at least 240 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, at least 290 MPa, at least 300 MPa, at least 310 MPa, at least 320 MPa, at least 330 MPa, at least 340 MPa, at least 350 MPa, or anywhere in between.
In certain aspects, the aluminum alloys can have an ultimate tensile strength (UTS) of at least 170 MPa. In non-limiting examples, the UTS is at least 170 MPa, at least 180 MPa, at least 190 MPa, at least 200 MPa, at least 210 MPa, at least 220 MPa, at least 230 MPa, at least 240 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, at least 290 MPa, at least 300 MPa, at least 310 MPa, at least 320 MPa, at least 330 MPa, at least 340 MPa, at least 350 MPa, or anywhere in between. In some cases, the UTS is from 200 MPa to 320 MPa. For example, the UTS can be from 200 MPa to 320 MPa, from 190 MPa to 290 MPa, from 300 MPa to 350 MPa, from 180 MPa to 340 MPa, or from 175 MPa to 325 MPa.
In some examples, the alloys described herein provided in an O temper can have an UTS of from at least 170 MPa to 250 MPa. In non-limiting examples, the UTS of the alloys in O temper is at least 170 MPa, at least 180 MPa, at least 190 MPa, at least 200 MPa, at least 210 MPa, at least 220 MPa, at least 230 MPa, at least 240 MPa, at least 250 MPa, or anywhere in between.
In some further examples, the alloys described herein in an H temper can have an UTS of at least 200 MPa, at least 210 MPa, at least 220 MPa, at least 230 MPa, at least 240 MPa, at least 250 MPa, at least 260 MPa, at least 270 MPa, at least 280 MPa, at least 290 MPa, at least 300 MPa, at least 310 MPa, at least 320 MPa, at least 330 MPa, at least 340 MPa, at least 350 MPa, or anywhere in between.
In certain aspects, the alloy encompasses any yield strength that has sufficient formability to meet an elongation of 9.75 % or greater in the O temper (e.g., 10.0 % or greater). In certain examples, the elongation can be 9.75 % or greater, 10.0 % or greater, 10.25 % or greater, 10.5 % or greater, 10.75 % or greater, 11.0 % or greater, 11.25 % or greater, 11.5 % or greater, 11.75 % or greater, 12.0 % or greater, 12.25 % or greater, 12.5 % or greater, 12.75 % or greater, 13.0 % or greater, 13.25 % or greater, 13.5 % or greater, 13.75 % or greater, 14.0 % or greater, 14.25 % or greater, 14.5 % or greater, 14.75 % or greater, 15.0 % or greater, 15.25 % or greater, 15.5 % or greater, 15.75 % or greater, 16.0 % or greater, 16.25 % or greater, 16.5 % or greater, or anywhere in between.
In certain aspects, the alloy can have a corrosion resistance that provides a negative corrosion potential or electrochemical potential (Ecorr) of about -700 mV or less when tested according to the ASTM G69 standard. In certain cases, an open corrosion potential value vs. Standard Calomel Electrode (SCE) can be -700 mV or less, -710 mV or less, -720 mV or less, - 730 mV or less, -740 mV or less, -750 mV or less, -760 mV or less, -770 mV or less, -780 mV or less, -790 mV or less, -800 mV or less, -810 mV or less, -820 mV or less, -830 mV or less, - 840 mV or less, -850 mV or less, or anywhere in between. For example, the aluminum alloy can have an open corrosion potential of from -740 mV to -850 mV (e.g., from -750 mV to - 840 mV or from -770 mV to -830 mV).
In some examples, the alloy can have an average conductivity value of above 36 % based on the international annealed copper standard (IACS) (e.g., from 37 % IACS to 44 % IACS). For example, the alloy can have an average conductivity value of 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44 %, or anywhere in between. All values in % IACS.

Methods of Preparing and Processing

In certain aspects, the disclosed alloy composition is a product of a disclosed method. Without intending to limit the disclosure, aluminum alloy properties are partially determined by the formation of microstructures during the alloy's preparation. In certain aspects, the method of preparation for an alloy composition may influence or even determine whether the alloy will have properties adequate for a desired application.

Casting

The alloy described herein can be cast using a casting method as known to those of skill in the art. For example, the casting process can include a Direct Chill (DC) casting process. The DC casting process is performed according to standards commonly used in the aluminum industry as known to one of skill in the art. The DC process can provide an ingot. Optionally, the ingot can be scalped before downstream processing. Optionally, the casting process can include a continuous casting (CC) process.
The cast aluminum alloy can then be subjected to further processing steps. For example, the processing methods as described herein can include the steps of homogenization, hot rolling, cold rolling, and/or annealing.

Homogenization

The homogenization step can include heating a cast aluminum alloy as described herein to attain a homogenization temperature of or at least 570 °C (e.g., at least 570 °C, at least 580 °C, at least 590 °C, at least 600 °C, at least 610 °C, or anywhere in between). For example, the cast aluminum alloy can be heated to a temperature of from 570 °C to 620 °C, from 575 °C to 615 °C, from 585 °C to 610 °C, or from 590 °C to 605 °C. In some cases, the heating rate to the homogenization temperature can be 100 °C/hour or less, 75 °C/hour or less, 50 °C/hour or less, 40 °C/hour or less, 30 °C/hour or less, 25 °C/hour or less, 20 °C/hour or less, 15 °C/hour or less, or 10 °C/hour or less. In other cases, the heating rate to the homogenization temperature can be from 10 °C/min to 100 °C/min (e.g., 10 °C/min to 90 °C/min, 10 °C/min to 70 °C/min, 10 °C/min to 60 °C/min, from 20 °C/min to 90 °C/min, from 30 °C/min to 80 °C/min, from 40 °C/min to 70 °C/min, or from 50 °C/min to 60 °C/min).
The cast aluminum alloy is then allowed to soak (i.e., held at the indicated temperature) for a period of time. According to one non-limiting example, the cast aluminum alloy is allowed to soak for up to 5 hours (e.g., from 10 minutes to 5 hours, inclusively). For example, the cast aluminum alloy can be soaked at a temperature of at least 570 °C for 10 minutes, 20 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or anywhere in between.
The cast aluminum alloy can be cooled from the first temperature to a second temperature that is lower than the first temperature. In some examples, the second temperature is greater than 555 °C (e.g., greater than 560 °C, greater than 565 °C, greater than 570 °C, or greater than 575 °C). For example, the cast aluminum alloy can be cooled to a second temperature of from 555 °C to about 590 °C, from 560 °C to 575 °C, from 565 °C to 580 °C, from 570 °C to 585 °C, from 565 °C to 570 °C, from 570 °C to 590 °C, or from 575 °C to 585 °C. The cooling rate to the second temperature can be from 10 °C/min to 100 °C/min (e.g., from 20 °C/min to 90 °C/min, from 30 °C/min to 80 °C/min, from 10 °C/min to 90 °C/min, from 10 °C/min to 70 °C/min, from 10 °C/min to 60 °C/min, from 40 °C/min to 70 °C/min, or from 50 °C/min to 60 °C/min).
The cast aluminum alloy can then be allowed to soak at the second temperature for a period of time. In certain cases, the ingot is allowed to soak for up to 5 hours (e.g., from 10 minutes to 5 hours, inclusively). For example, the ingot can be soaked at a temperature of from 560 °C to 590 °C for 10 minutes, 20 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or anywhere in between.

Hot Rolling

Following the homogenization step, a hot rolling step can be performed. In certain cases, the cast aluminum alloys are hot-rolled with a hot mill entry temperature range of 560 °C to 600 °C. For example, the entry temperature can be 560 °C, 565 °C, 570 °C, 575 °C, 580 °C, 585 °C, 590 °C, 595 °C, or 600 °C. In certain cases, the hot roll exit temperature can range from 290 °C to 350 °C (e.g., from 310 °C to 340 °C). For example, the hot roll exit temperature can be 290 °C, 295 °C, 300 °C, 305 °C, 310 °C, 315 °C, 320 °C, 325 °C, 330 °C, 335 °C, 340 °C, 345 °C, 350 °C, or anywhere in between.
In certain cases, the cast aluminum alloy can be hot rolled to an 2 mm to 15 mm thick gauge (e.g., from 2.5 mm to 12 mm thick gauge). For example, the cast aluminum alloy can be hot rolled to an 2 mm thick gauge, 2.5 mm thick gauge, 3 mm thick gauge, 3.5 mm thick gauge, 4 mm thick gauge, 5 mm thick gauge, 6 mm thick gauge, 7 mm thick gauge, 8 mm thick gauge, 9 mm thick gauge, about 10 mm thick gauge, about 11 mm thick gauge, about 12 mm thick gauge, 13 mm thick gauge, 14 mm thick gauge, or 15 mm thick gauge. In certain cases, the cast aluminum alloy can be hot rolled to a gauge greater than 15 mm (i.e., a plate). In other cases, the cast aluminum alloy can be hot rolled to a gauge less than 4 mm (i.e., a sheet).

Cold Rolling

A cold rolling step can be performed following the hot rolling step. In certain aspects, the rolled product from the hot rolling step can be cold rolled to a sheet (e.g., below 4.0 mm). In certain aspects, the rolled product is cold rolled to a thickness of 0.4 mm to 1.0 mm, 1.0 mm to 3.0 mm, or 3.0 mm to less than 4.0 mm. In certain aspects, the alloy is cold rolled to 3.5 mm or less, 3 mm or less, 2.5 mm or less, 2 mm or less, 1.5 mm or less, 1 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, or 0.1 mm or less. For example, the rolled product can be cold rolled to 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3.0 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4.0 mm, or anywhere in between.
In one case, the method for processing the aluminum alloys as described herein can include the following steps. A homogenization step can be performed by heating a cast aluminum alloy as described herein to attain a homogenization temperature of 590 °C over a time period of about 12 hours, wherein the cast aluminum alloys are allowed to soak at a temperature of 590 °C for about 2 hours. The cast aluminum alloys can then be cooled to 580 °C and allowed to soak for 2 hours at 580 °C. The cast aluminum alloys can then be hot rolled to a gauge of 2.5 mm thick. The cast aluminum alloys can then be cold rolled to a gauge of less than 1.0 mm thick (e.g., 1.0 mm or less or 0.15 mm or less), providing an aluminum alloy sheet.

Annealing

Optionally, the aluminum alloy sheet can be annealed by heating the sheet from room temperature to an annealing temperature of from 200 °C to 400 °C (e.g., from 210 °C to 375 °C, from 220 °C to 350 °C, from 225 °C to 345 °C, or from 250 °C to 320 °C). In some cases, the heating rate to the annealing temperature can be 100 °C/hour or less, 75 °C/hour or less, 50 °C/hour or less, 40 °C/hour or less, 30 °C/hour or less, 25 °C/hour or less, 20 °C/hour or less, 15 °C/hour or less, or 10 °C/hour or less. The sheet can soak at the temperature for a period of time. In certain aspects, the sheet is allowed to soak for up to approximately 6 hours (e.g., from 10 seconds to 6 hours, inclusively). For example, the sheet can be soaked at the temperature of from 230 °C to 370 °C for 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 60 seconds, 65 seconds, 70 seconds, 75 seconds, 80 seconds, 85 seconds, 90 seconds, 95 seconds, 100 seconds, 105 seconds, 110 seconds, 115 seconds, 120 seconds, 125 seconds, 130 seconds, 135 seconds, 140 seconds, 145 seconds, 150 seconds, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes, 85 minutes, 90 minutes, 95 minutes, 100 minutes, 105 minutes, 110 minutes, 115 minutes, 120 minutes, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, or anywhere in between. In some examples, the sheet is not annealed.
In some examples, the sheet is heated to an annealing temperature of 200 °C to 400 °C at a constant rate of 40 °C/hour to 50 °C/hour. In some aspects, the sheet is allowed to soak at the annealing temperature for 3 hours to 5 hours (e.g., for 4 hours). In some cases, the sheet is cooled from the annealing temperature at a constant rate of 40 °C/hour to 50 °C/hour. In some examples, the sheet is not annealed.

Methods of Using

The alloys and methods described herein can be used in industrial applications including sacrificial parts, heat dissipation, packaging, and building materials. The alloys described herein can be employed as industrial fin stock for heat exchangers. The industrial fin stock can be provided such that it is more resistant to corrosion than currently employed industrial fin stock alloys (e.g., AA7072 and AA1100) and will still preferentially corrode protecting other metal parts incorporated in a heat exchanger. The aluminum alloys disclosed herein are suitable substitutes for metals conventionally used in indoor and outdoor HVAC units. As used herein, the meaning of "indoor" refers to a placement contained within any structure produced by humans with controlled environmental conditions. As used herein, the meaning of "outdoor" refers to a placement not fully contained within any structure produced by humans and exposed to geological and meteorological environmental conditions comprising air, solar radiation, wind, rain, sleet, snow, freezing rain, ice, hail, dust storms, humidity, aridity, smoke (e.g., tobacco smoke, house fire smoke, industrial incinerator smoke and wild fire smoke), smog, fossil fuel exhaust, bio-fuel exhaust, salts (e.g., high salt content air in regions near a body of salt water), radioactivity, electromagnetic waves, corrosive gases, corrosive liquids, galvanic metals, galvanic alloys, corrosive solids, plasma, fire, electrostatic discharge (e.g., lightning), biological materials (e.g., animal waste, saliva, excreted oils, vegetation), wind-blown particulates, barometric pressure change, and diurnal temperature change. The aluminum alloys described herein provide better corrosion performance and higher strength as compared to alloys currently employed.
The following examples will serve to further illustrate the present invention without, however, constituting any limitation thereof. During the studies described in the following examples, conventional procedures were followed, unless otherwise stated. Some of the procedures are described below for illustrative purposes.

EXAMPLES

Example 1: Mechanical Properties

Exemplary and comparative alloys, as shown in Table 5, were prepared according to the methods described herein.

Alloys

1, 2, 3, and 4 are exemplary alloys created according to methods described herein. Alloy 5 is a comparative alloy prepared according to methods described herein. Alloy A is AA7072, which is currently employed as an industrial fin stock in commercial applications. Alloy B is AA1100, which is currently employed as an industrial fin stock in commercial applications.

Table 5

Alloy	Zn	Si	Fe	Cu	Mn	Mg	Cr	Ti
1	1.00	0.29	0.51	0.16	0.86	1.2	0.001	0.011
2	1.53	0.3	0.51	0.17	0.87	1.21	0.001	0.016
3	2.04	0.29	0.51	0.17	0.87	1.21	0.001	0.015
4	2.54	0.29	0.51	0.17	0.88	1.23	0.001	0.012
5	0.15	0.22	0.31	0.07	1.00	1.02	0.001	0.16
Comp. A	1.3	0.07	0.37	0.01	0.03	0.03	0.02	0.03
Comp. B	0.1	0.165	0.55	0.075	0.02	0.01	0.02	0.03

All expressed as wt. %.

The mechanical properties of the exemplary alloys and comparative alloys were determined according to ASTM B557. Specifically, the alloys were subjected to tensile, elongation, and conductivity tests. The yield strength (YS), ultimate tensile strength (UTS), percent elongation (EI), and percent of the International Annealed Copper Standard (% IACS) were determined. The test results are summarized in Table 6.

Table 6

Alloy	Gauge (mm)	YS (MPa)	UTS (MPa)	EI (%)	%IACS	YS (MPa)	UTS (MPa)	EI (%)	%IACS	YS (MPa)	UTS (MPa)	EI (%)	%IACS
Alloy	Gauge (mm)	H19				H23				O
1	0.155	289	296	1.77	39.6	210	241	6.94	41.6	67	171	16.38	42.0
2	0.161	299	307	2.37	42.6	207	239	7.09	41.7	109	183	12.93	43.6
3	0.156	300	308	2.18	40.8	206	236	6.99	41.7	78	190	13.63	39.2
4	0.160	309	318	2.14	40.7	212	240	6.46	41.7	85	205	14.31	43.8
5	0.152	289	297	1.98	36.0	204	230	5.58	36.6	160	206	9.78	39.1
Comp. A	0.178	196	213	5.1	59	-	-	-	-	-	-	-	-
Comp. B*	0.102	-	-	-	-	108	122.0	20.4	60.3	-	-	-	-

*Comp. B temper was in H22 temper during testing.

Evident in the tensile test results is the excellent strength of the exemplary alloys compared to alloys currently employed as industrial fin stock. The exemplary alloys exhibited an average conductivity of about 37 - 44 % IACS. As shown above in Table 6, the exemplary alloys described herein display exceptional mechanical properties as compared to the comparative alloys and can be excellent commercial alloys employed in industrial fin stock applications.

Example 2: Corrosion Properties

The corrosion properties of exemplary alloys described herein and comparative alloys described herein, elemental compositions of which are provided in Table 5, were determined. In addition, the corrosion properties of two additional comparative tube alloys were determined. Comp. Alloy C is an aluminum tube alloy containing 0.15 wt. % Zn and Comp. Alloy D is an AA1235 aluminum alloy commonly used in heat exchangers. The open circuit potential corrosion values were measured according to ASTM G69. Corrosion test results are summarized in Table 7. The aluminum tube alloys Comp. Alloy C and Comp. Alloy D had an average open corrosion potential value vs. SCE of -741mV.

Table 7

Alloy	Zn (wt. %)	Ecorr(mV) vs. SCE
Alloy	Zn (wt. %)	H19	H23	O
1	1.00	-747	-749	-739
2	1.53	-778	-759	-779
3	2.04	-792	-761	-794
4	2.54	-809	-766	-821
5	0.15	-731	-730	-730
Comp. A	1.30	-886	-	-
Comp. B*	0.10	-	-731	-
Comp. C				-741
Comp. D				-742

*Alloy AA1100 temper was in H22 temper during testing.

The differences in corrosion resistance values between Alloys 1-5 and Comp. Alloy C are shown below in Table 8. Table 8

Alloy Zn (wt. %) ΔEcorr(mV)

H19 H23 O

1 1.00 6 8 -2

2 1.53 37 18 38

3 2.04 51 20 53

4 2.54 68 25 80

5 0.15 -10 -11 -11
The differences in corrosion resistance values between Alloys 1-5 and Comp. Alloy D are shown below in Table 9. Table 9

Alloy Zn (wt. %) ΔEcorr(mV)

H19 H23 O

1 1.00 5 7 -3

2 1.53 36 17 37

3 2.04 50 19 52

4 2.54 67 24 79

5 0.15 -11 -12 -12
The exemplary alloys in all tempers (e.g., H19, H23, and O) exhibited electrochemical potential values comparable to the comparative alloys. The differences between Alloys 1-5 and Comp. Alloy C and between Alloys 1-5 and Comp. Alloy D ranged from 15-80 mV. The data show that Alloys 2, 3, 4 and 5 are acceptable to prepare fins that act as sacrificial anodes.
Exemplary alloys with varying Zn subjected to electrochemical corrosion testing also exhibited a nearly linear correlation between Zn content and electrochemical potential. On average, an increase of 0.1 wt. % Zn provided an increase of about 9 mV in electrochemical potential. Exemplary alloys with a Zn content of about 2.5 wt. % or greater exhibited more negative corrosion potential, indicating that incorporating Zn greater than about 2.5 wt. % may not be desirable for achieving certain properties. Zn can be added optimally to be sufficiently resistant to corrosion to serve as a sacrificial alloy in a heat exchanger yet still preferentially corrode ahead of any primary functional metal parts of a heat exchanger, further suggesting the exemplary alloys described herein are excellent replacements for currently employed alloys used in industrial fin stock.
The corrosion properties of the exemplary alloys described herein and the comparative alloys described herein according to ASTM G71 were also determined. Specifically, the corrosion properties were measured using zero resistance ammetry (ZRA). The ZRA galvanic compatibility was measured where the exemplary alloys were used as fin stock and Comp. Alloy C and Comp. Alloy D were used as tubestock. The results shown in Tables 10 and 11 represent the average current for the last four hours of the cycle as performed according to the test method. Table 10 shows the ZRA results for Alloys 1-5 galvanically coupled to Comp. Alloy C. Table 10

Alloy Zn (wt. %) Average Current (µA/cm²)

H19 H23

1 1.00 26 35

2 1.53 29 24

3 2.04 30 37

4 2.54 27 26

5 0.15 -23 -15
As shown in Table 10, Alloys 1, 2, 3, and 4, containing from 1 to 2.5 wt. % Zn, displayed a positive corrosion current indicating that the exemplary fin alloys provided sacrificial protection to the tube alloys.
Table 11 shows the ZRA results for Alloys 1-5 galvanically coupled to Comp. Alloy D. Table 11

Alloy Zn (wt. %) Average Current (µA/cm²)

H19 H23

1 1.00 -30 12.8

2 1.53 10 15

3 2.04 13 4.5

4 2.54 25 9.1

5 0.15 -25 -29
As shown in Table 11, Alloys 1, 2, 3, and 4, containing from 1 to 2.5 wt. % Zn, displayed lower corrosion currents than exemplary alloys coupled with Comp. Alloy C, but still provided sacrificial protection to the tube alloy. All the exemplary fin alloys showed that a protective current was being provided to the Comp. Alloy C and Comp. Alloy D tubes throughout the test period.
The compatibilities of exemplary fin alloys attached to comparative tube alloys Comp. Alloy C and Comp. Alloy D were also evaluated according to ASTM G85 Annex 3. Synthetic sea water, acidified to 2.8-3.0 pH, was used. The exemplary fin samples were mechanically assembled to the tube alloys and subjected to corrosion testing for an exposure of 4 weeks. As shown in Figures 1 and 2, the samples displayed progressively more corrosion on the exemplary alloys as the zinc content increased from 2 % to 2.5 %. This is particularly true for the exemplary alloys coupled to Comp. Alloy D. Based on these data, Zn levels less than 2 wt. % are preferred in some instances, but can be optimized depending on tube composition.
The aluminum alloys described herein provide sacrificial corrosion characteristics and mechanical characteristics which enable the manufacture of aluminum alloy fin stock of reduced metal thickness. The fin stock of reduced metal thickness maintains sacrificial protection for the copper or aluminum alloy tubes in contact with the fins. The aluminum alloys described herein can also be used in other situations where mechanical strength in combination with sacrificial characteristics are desired.

Claims

An aluminum alloy comprising 0.7 - 3.0 wt. % Zn, 0.15 - 0.35 wt. % Si, 0.25 - 0.65 wt. % Fe, 0.05 - 0.20 wt. % Cu, 0.75 - 1.50 wt. % Mn, 0.50 - 1.50 wt. % Mg, up to 0.10 wt. % Cr, up to 0.10 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al.
The aluminum alloy of claim 1, comprising 1.0 - 2.5 wt. % Zn, 0.2 - 0.35 wt. % Si, 0.35 - 0.60 wt. % Fe, 0.10 - 0.20 wt. % Cu, 0.75 - 1.25 wt. % Mn, 0.90 - 1.30 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al.
The aluminum alloy of claim 1, comprising 1.5 - 2.5 wt. % Zn, 0.17 - 0.33 wt. % Si, 0.30 - 0.55 wt. % Fe, 0.15 - 0.20 wt. % Cu, 0.80 - 1.00 wt. % Mn, 1.00 - 1.25 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al.
The aluminum alloy of claim 1, comprising 0.9 - 2.6 wt. % Zn, 0.2 - 0.33 wt. % Si, 0.49 - 0.6 wt. % Fe, 0.15 - 0.19 wt. % Cu, 0.79 - 0.94 wt. % Mn, 1.13 - 1.27 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al.
The aluminum alloy of claim 1, comprising 1.4 - 1.6 wt. % Zn, 0.2 - 0.33 wt. % Si, 0.49 - 0.6 wt. % Fe, 0.15 - 0.19 wt. % Cu, 0.79 - 0.94 wt. % Mn, 1.13 - 1.27 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al.
A fin stock comprising the aluminum alloy of any one of claims 1-5.
The fin stock of claim 6, wherein a gauge of the fin stock is 1.0 mm or less.
The fin stock of claim 6 , wherein a gauge of the fin stock is 0.15 mm or less.
An article comprising a tube and a fin, wherein the fin comprises the fin stock according to any one of claims 6-8.
A method of producing a metal product, comprising:
casting an aluminum alloy to form a cast aluminum alloy, wherein the aluminum alloy comprises 0.7 - 3.0 wt. % Zn, 0.15 - 0.35 wt. % Si, 0.25 - 0.65 wt. % Fe, 0.05 - 0.20 wt. % Cu, 0.75 - 1.50 wt. % Mn, 0.50 - 1.50 wt. % Mg, up to 0.05 wt. % Cr, up to 0.05 wt. % Ti, and up to 0.15 wt. % of impurities, with the remainder as Al;

homogenizing the cast aluminum alloy;

hot rolling the cast aluminum alloy to produce a rolled product; and

cold rolling the rolled product to a final gauge product.
The method of claim 10, further comprising annealing the final gauge product.
An aluminum alloy product, wherein the aluminum alloy product is prepared by the method of claim 10 or 11.
The aluminum alloy product of claim 12, wherein the aluminum alloy product comprises a heat exchanger fin.