This application relates to a family of 5000-series aluminum alloys with high strength, good ductility, high creep resistance, high thermal stability and durability. The disclosed alloys are especially advantageous for, but not limited to, improving performance of beverage can lids and tabs. Additionally, the disclosed alloys are, for example, advantageous for improving performance of roofing and siding materials, chemical and food equipment, storage tanks, home appliances, sheet-metal work, marine parts, transportation parts, heavy duty cooking utensils, hydraulic tubes, fuel tanks, pressure vessels, heavy-duty truck and trailer bodies and assemblies, drilling rigs, missile components, and railroad cars.
The production of aluminum cans, largely to store beverages, is the single largest usage of aluminum in the world. The annual production is a staggering 320 billion cans per year, equating to 4.16 billion kilograms of aluminum. In addition, aluminum canning is likely the world's best example of recycling, as 75% of the aluminum used in cans is recycled. The production of aluminum cans is enormous, so an efficiency improvement comes with a giant multiplicative effect; a single gram of weight saved in the can may save over 200 thousand metric tons of aluminum globally per year. Together with this weight benefit, the energy consumption as well as the CO2 emissions during transport are reduced—both key metrics in sustainability of the environment. Additionally, the lightness of aluminum cans helps save resources during filling, storage, transportation and scrap at the end of the product's life. Thus lightweighting the can has been a front-burner issue for decades.
The beverage packaging industry is constantly seeking ways to maintain the can's performance while continuing to trim the materials as much as possible. A common can design consists of two pieces: the can body is made of 3000-series aluminum, specifically AA3004, while the can lid and opener are made from 5000-series aluminum, specifically AA5182. The success behind the consistent and precise production of aluminum cans is based on the strong yet formable 3000- and 5000-series aluminum sheets. The can body is about 75% of the can's mass, while the smaller lid claims the rest, 25%. Two most obvious ways to design a lighter can are: (i) designing a smaller lid and (ii) reducing thickness of the can's wall and lid. To thin the can body and lid, stronger 3000-series and 5000-series alloys are needed, while maintaining important characteristics, such as density, formability and corrosion resistance. Aerospace-grade 2000- and 7000-series are very strong, but their low formability is not suitable for canning. Thus the common approach to develop new canning materials is to modify the currently utilized alloys, that is, modifying alloy composition and thermo-mechanical processes to the current 3000-series and 5000-series alloys to strengthen them without sacrificing other important properties. Moreover, 75% of the aluminum in cans is recycled and is currently being used to recast aluminum sheets, which are returned to can manufacturers to produce new batches of cans. Recycling plays a significant role in the economics of canning, thus modifying the current 3000-series and 5000-series alloys will help maintain the usage of low-cost recycled cans.
A well-known means to enhance the strength and maintain the ductility of commercial aluminum alloys is the addition of small concentrations of Scandium (Sc). The strengthening originates from the creation during aging of L12-structured Al3Sc nano-precipitates (˜5-10 nm in diam.) which are coherent with the aluminum matrix. The small volume fraction, nano-size and matrix coherency of these precipitates help the alloys maintain other properties, such as ductility and formability. Scandium, however, is extremely costly (ten-fold more expensive than silver), severely prohibiting its usage in cost-sensitive applications such as food and drink packaging.
Accordingly, stronger 5000-series aluminum alloys are needed, while maintaining important characteristics, such as density, formability and corrosion resistance. With a stronger material, the can's lid and tab can be made thinner, resulting in a lighter beverage can. In addition, higher performance 5000-series aluminum alloys are needed constantly in many other applications for lightweighting purposes.
The embodiments described herein relate to heat-treatable aluminum-magnesium-based (5000-series) alloys, containing an Al3Zr nanoscale precipitate, wherein the nanoscale precipitate has an average diameter of about 20 nm or less and has an L12 structure in an 60 -Al face centered cubic matrix, wherein the average number density of the nanoscale precipitate is about 2021 m−3 or more. They exhibit high strength, good ductility, high creep resistance, high thermal stability and durability, while being essentially free of scandium (i.e., no scandium is added intentionally).
5000-series aluminum alloys are strain-hardenable but not heat-treatable. They contain magnesium as the main alloying element, optionally with manganese, and typically have good strength, formability, and corrosion resistance. AA5182 aluminum alloy, containing 4-5Mg and 0.2-0.5Mn (wt. %), is currently being utilized for beverage can lids. It also is being used in automotive applications. The effect of Al3Zr nano-precipitates on the mechanical performance of this alloy was investigated.
Mechanical properties of Al-4.5Mg-0.35Mn-0.2Si wt. % (AA5182)and Al-4.5Mg-0.35Mn-0.2Si-0.3Zr-0.1Sn wt. % (invented alloy), after peak-aging and cold rolling are displayed in
Additionally,
Table 1 lists mechanical properties of thin sheets (0.25 mm in thickness) of Al-4.5Mg-0.25Mn-0.2Fe-0.09Si wt. % (AA5182) in hard-temper (example alloy 1) and soft temper (example alloy 2), Al-4.5Mg-0.25Mn-0.2Fe-0.09Si-0.3Zr-0.1Sn wt. % (AA5182-nano) in hard-temper (invented alloy 1) and soft temper (invented alloy 2). AA5182 hard-temper is a common aluminum alloy for beverage can lids, whereas AA5182 soft-temper is commonly used in automotive applications. The AA5182-nano alloy, in both hard- and soft-tempers (invented alloys 1 and 2) achieve higher yield strength and tensile strength, while maintaining essentially the same elongation at break, compared to the AA5182 alloy with the respective tempers (example alloy 1 and 2). The thin sheets of the alloys in Table 1 were fabricated by the following steps: casting, hot-rolling, annealing, cold-rolling, and stabilizing heat treatment for hard-temper; and casting, hot-rolling, cold rolling, and annealing for soft-temper.
The disclosed aluminum alloys are essentially free of scandium, which is understood to mean that no scandium is added intentionally. Addition of scandium in aluminum alloys is advantageous for mechanical properties. For example, it is described in U.S. Pat. No. 5,624,632, which is incorporated herein by reference. However, scandium is very expensive (ten times more expensive than silver), severely limiting its practical applications.
Zirconium, with a concentration of up to about 0.3 wt. %, is sometimes added to aluminum alloys for grain refining. The refined grain structure helps improve castability, ductility, and workability of the final product. An example is described in U.S. Pat. No. 5,976,278, which is incorporated herein by reference. In the present application, zirconium with a concentration of less than about 0.5 wt. %, and preferably less than about 0.4 wt. %, is added together with an inoculant element to form Al3Zr nano-precipitates, wherein the nanoscale precipitate has an average diameter of about 20 nm or less and has an L12 structure in an α-Al face centered cubic matrix, and wherein the average number density of the nanoscale precipitate is about 2021 m−3 or more, with a purpose to improve mechanical strength, ductility, creep resistance, thermal stability and durability of the based alloys. Generally, a zirconium concentration of more than about 0.2 wt. % is needed so that Zr atoms have enough driving force to form Al3Zr nano-precipitates.
Disclosed aluminum alloys comprise an inoculant, wherein the inoculant comprises one or more of tin, strontium, zinc, gallium, germanium, arsenic, indium, antimony, lead, and bismuth. The presence of an inoculant accelerates precipitation kinetics of Al3Zr nano-precipitates, thus these precipitates can be formed within a practical amount of time during heat-treatment. In the other words, the beneficial Al3Zr nano-precipitates can be formed within a few hours of heat treatment, with the presence of the inoculant, compared to between a few weeks and a few months of heat treatment without the presence of an inoculant. Among all inoculant elements, tin appears to be the best performer in terms of accelerating precipitation kinetics of Al3Zr nano-precipitates. A tin concentration of less than about 0.2% is needed for the mentioned purpose. Beyond this value, tin will form bubbles and/or a liquid phase in the aluminum solid matrix, which is detrimental for the mechanical properties. For example, this behavior is described in U.S. Pat. No. 9,453,272, which is incorporated herein by reference.
In one embodiment, an aluminum alloy comprises aluminum, magnesium, manganese, silicon, zirconium, and an inoculant, and including a nanoscale precipitate comprising Al3Zr, wherein the nanoscale precipitate has an average diameter of about 20 nm or less and has an L12 structure in an α-Al face centered cubic matrix, wherein the average number density of the nanoscale precipitate is about 2021 m−3 or more, and wherein the inoculant comprises one or more of tin, strontium, and zinc.
In one embodiment, if an aluminum alloy is in hard temper it possesses a yield strength of at least about 380 MPa, a tensile strength of at least about 440 MPa, and an elongation at least about 5% at room temperature.
In one embodiment, if an aluminum alloy is in soft temper it possesses a yield strength of at least about 190 MPa, a tensile strength of at least about 320 MPa, and an elongation of at least about 18% at room temperature.
In one embodiment, an aluminum alloy possesses a recrystallization temperature of about 300° C.
In one embodiment, an aluminum alloy comprises about 3.0 to about 6.2% by weight magnesium; about 0.01 to about 1.8% by weight manganese; about 0.01 to about 0.2% by weight silicon; about 0.2 to about 0.5% by weight zirconium; about 0.01 to about 0.2% by weight tin; and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises about 3.0 to about 6.2% by weight magnesium; about 0.01 to about 1.8% by weight manganese; about 0.01 to about 0.2% by weight silicon; about 0.2 to about 0.5% by weight zirconium; about 0.001 to about 0.1% by weight strontium; and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises about 3.0 to about 6.2% by weight magnesium; about 0.01 to 1.8% by weight manganese; about 0.01 to about 0.2% by weight silicon; about 0.2 to about 0.5% by weight zirconium; about 0.1 to about 1% by weight zinc; and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises a plurality of L12 precipitates having an average diameter of about 10 nm or less.
In one embodiment, an aluminum alloy comprises a plurality of L12 precipitates having an average diameter of about 3 nm to about 7 nm.
In one embodiment, an aluminum alloy comprises about 4.% by weight magnesium, about 0.35% by weight Manganese, about 0.2% by weight silicon, about 0.3% by weight zirconium, about 0.1% by weight tin, and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises about 4.5% by weight magnesium, about 0.35% by weight manganese, about 0.2% by weight silicon, about 0.3% by weight zirconium, about 0.003% by weight strontium, and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises about 4.5% by weight magnesium, about 0.35% by weight manganese, about 0.2% by weight silicon, about 0.3% by weight zirconium, about 0.5% by weight zinc, and aluminum as the remainder.
In one embodiment, an aluminum alloy comprises no more than about 0.5% iron as an impurity element.
In one embodiment, an aluminum alloy comprises aluminum, magnesium, manganese, silicon, zirconium, and an inoculant, and including a nanoscale precipitate comprising Al3Zr, wherein the nanoscale precipitate has an average diameter of about 20 nm or less and has an L12 structure in an α-Al face centered cubic matrix, wherein the average number density of the nanoscale precipitate is about 2021 m−3 or more, and wherein the inoculant comprises one or more of gallium, germanium, arsenic, indium, antimony, lead, and bismuth.
One method for manufacturing a component from a disclosed aluminum alloy comprises: a) melting the alloy at a temperature of about 700 to about 900° C.; b) then casting the melted alloy into casting molds at ambient temperature; c) then using a cooling medium to cool the cast ingot; and d) then heat aging the cast ingot at a temperature of about 350° C. to about 450° C. for a time of about 2 to about 48 hours. In one embodiment, the method further comprises cold rolling the cast ingot to form a sheet product. In one embodiment, the method further comprises a final stabilizing heat treatment of the sheet product at a temperature of about 140° C. to about 170° C. for a time of about 1 to about 5 hours. In some embodiments, the cooling medium can be air, water, ice, or dry ice, The heat aging step stated above (350-450° C. for 2-48 hours) is determined to be peak-aging for components comprising the disclosed aluminum alloys. When a component manufactured from a disclosed aluminum alloy is peak-aged, the microstructure of the component is thermally stable and is unchanged by exposure to elevated temperatures for extended times.
Another method for manufacturing a component from a disclosed aluminum alloy comprises: a) melting the alloy at a temperature of about 700 to 900° C.; b) then casting the alloy into casting molds at ambient temperature; c) then using a cooling medium to cool the cast ingot; and d) then hot rolling the cast ingot into a sheet. In one embodiment, the method further comprises then heat aging the sheet at a temperature of about 350° C. to about 450° C. for a time of about 2 to about 48 hours. In one embodiment, the method further comprises then cold rolling the sheet, after the heat aging step, to form a thin sheet or foil product. In one embodiment, the method further comprises a final stabilizing heat treatment of the thin sheet or foil product at a temperature of about 140° C. to about 170° C. for a time of about 1 to about 5 hours.
Another method for manufacturing a component from a disclosed aluminum alloy comprises: a) melting the alloy at a temperature of about 700 to 900° C.; b) then casting the alloy into casting molds at ambient temperature; c) then using a cooling medium to cool the cast ingot; d) then hot rolling the cast ingot into a sheet; e) then cold rolling the sheet to form a thin sheet or foil product; and f) then heat aging the thin sheet or foil product at a temperature of about 300° C. to about 410° C. for a time of about 2 to about 24 hours.
Some applications for the disclosed alloys include, for example, beverage can lids, beverage can tabs, roofing materials, siding materials, chemical manufacturing equipment, food manufacturing equipment, storage tanks, home appliances, sheet-metal work, marine parts, transportation parts, heavy duty cooking utensils, hydraulic tubes, fuel tanks, pressure vessels, truck bodies, truck assemblies, trailer bodies, trailer assemblies, drilling rigs, missile components, and railroad cars. Some fabricated forms of the disclosed aluminum alloys include, for example, wires, sheets, plates and foils.
From the foregoing, it will be understood that numerous modifications and variations can be effectuated without departing from the true spirit and scope of the novel concepts of the present invention. It is to be understood that no limitation with respect to the specific embodiments illustrated and described is intended or should be inferred.
The present application claims the benefit of the filing date of U.S. Ser. No. 62/468,467, filed 8 Mar. 2017 and titled High-Performance 5000-Series Aluminum Alloys, the contents of which are incorporated herein by reference.
This invention was made with government support under Federal Award No. IIP 1549282, awarded by National Science Foundation. The Government has certain rights in the invention.
Number | Date | Country | |
---|---|---|---|
62468467 | Mar 2017 | US |
Number | Date | Country | |
---|---|---|---|
Parent | PCT/US2018/020899 | Mar 2018 | US |
Child | 16562981 | US |