Patent Application
20140127076
Aluminum alloys are useful in a variety of applications. However, improving one property of an aluminum alloy without degrading another property often proves elusive.
Broadly, the present disclosure relates to new 5xxx-lithium aluminum alloy products having an improved combination of properties. The new 5xxx-lithium aluminum alloy products are made from aluminum alloys containing from 3.75 to 5.0 wt. % magnesium (Mg), from 1.6 to 2.3 wt. % lithium (Li), from 0.50 to 2.5 wt. % zinc (Zn), 0.05 to 0.50 wt. % of a grain structure control element selected from the group consisting of Zr, Sc, Cr, V, Hf, other rare earth elements, and combinations thereof, optionally up to 1.0 wt. % copper (Cu), optionally up to 1.0 wt. % silver (Ag), wherein wt. % Cu+wt. % Ag≦1.15 wt. %, wherein, when the aluminum alloy contains not greater than 0.04 wt. % Cu and not greater than 0.04 wt. % Ag, the aluminum alloy contains at least 0.75 wt. % zinc, optionally up to 0.5 wt. % silicon (Si), optionally up to 1.0 wt. % manganese (Mn), optionally up to 0.25 wt. % Fe, optionally up to 0.15 wt. % Ti, the balance being aluminum, other elements and impurities, wherein the aluminum alloy contains not greater than 0.10 wt. % of any one of the other elements, and wherein the aluminum alloy contains not greater than 0.35 wt. % total of the other elements. The new 5xxx-lithium aluminum alloys may realize an improved combination of properties, such as an improved combination of two or more of strength, fracture toughness, density, fatigue crack growth, and/or corrosion resistance, among others. The new 5xxx-lithiurn aluminum alloys may be used in aerospace and defense applications, among others.
5xxx aluminum alloys are aluminum alloys having magnesium as the predominate alloying element other than aluminum. The new 5xxx-lithium aluminum alloys of the present patent application are 5xxx aluminum alloys having 3.75 to 5.0 wt. % Mg, from 1.6-2.3 wt. % Li, and from 0.5 to 2.5 wt. % Zn, among others, as described below. The new 5xxx-lithium aluminum alloy products are generally in the form of wrought products, and may be produced by casting the new 5xxx-lithium alloy, after which it is homogenized, then hot worked to an intermediate gauge or a final gauge, then optionally cold worked, then solution heat treated and quenched, then optionally cold worked, and then optionally artificially aged. Thus, the new 5xxx-lithium aluminum alloy products are generally in the T3 or T8 temper, such tempers being known to those skilled in the art and defined by the Aluminum Association. The above hot working step may be completed by rolling, extruding, or forging to produce a sheet or plate, an extrusion, or a forging, respectively.
The new 5xxx-lithium aluminum alloy products generally contain from 3.75 to 5.0 wt. % Mg. In one embodiment, a new 5xxx-lithium aluminum alloy product contains at least 4.0 wt. % Mg. In another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 4.1 wt. % Mg. In yet another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 4.2 wt. % Mg. In another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 4.3 wt. % Mg. In one embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 4.9 wt. % Mg. In another embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 4.8 wt. % Mg. In yet another embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 4.7 wt. % Mg. In another embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 4.6 wt. % Mg.
The new 5xxx-lithium aluminum alloy products generally contain from 1.60 to 2.30 wt. % Li. In one embodiment, a new 5xxx-lithium aluminum alloy product contains at least 1.65 wt. % Li. In another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 1.70 wt. % Li. In yet another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 1.75 wt. % Li. In one embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 2.20 wt. % Li. In another embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 2.10 wt. % Li.
The new 5xxx-lithium aluminum alloy products generally contain from 0.5 to 2.50 wt. % Zn. In one embodiment, a new 5xxx-lithium aluminum alloy product contains at least 0.60 wt. % Zn. In another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 0.70 wt. % Zn. In yet another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 0.80 wt. % Zn. In another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 0.90 wt. % Zn. In yet another embodiment, a new 5xxx-lithium aluminum alloy product contains at least 1.00 wt. % Zn. In one embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 2.25 wt. % Zn. In another embodiment, a new 5xxx-lithium aluminum alloy product contains not greater than 2.00 wt. % Zn.
The new 5xxx-lithium aluminum alloy products may optionally contain up to 1.0 wt. % copper (Cu). In embodiments where copper is used, the new 5xxx-lithium aluminum alloy products contain at least 0.05 wt. % Cu. In one embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.15 wt. % Cu. In another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.25 wt. % Cu. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.30 wt. % Cu. In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.90 wt. % Cu. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.80 wt. % Cu. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.70 wt. % Cu. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.60 wt. % Cu. In some embodiments copper is present as an impurity, and in these embodiments the new 5xxx-lithium aluminum alloy products contain not greater than 0.04 wt. % Cu.
The new 5xxx-lithium aluminum alloy products may optionally contain up to 1.0 wt. % silver (Ag). In embodiments where silver is used, the new 5xxx-lithium aluminum alloy products contain at least 0.05 wt. % Ag. In one embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.15 wt. % Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.25 wt. % Ag. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.30 wt. % Ag. In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.90 wt. % Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.80 wt. % Ag. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.70 wt. % Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.60 wt. % Ag. In some embodiments silver is present as an impurity, and in these embodiments the new 5xxx-lithium aluminum alloy products contain not greater than 0.04 wt. % Ag.
When the new 5xxx-lithium aluminum alloy products contain copper and silver, the new 5xxx-lithium aluminum alloy products contain not greater than 1.15 wt. %. Cu+Ag (i.e., (wt % Cu)+(wt. % Ag)≦1.15 wt. %). In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 1.10 wt. % Cu+Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 1.05 wt. % In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 1.00 wt. % Cu+Ag.
In embodiments where copper and/or or silver are used, the new 5xxx-lithium aluminum alloy products generally contain at least 0.15 wt. % Cu+Ag (i.e., (wt. % Cu)+(wt. % Ag)≧0.15 wt. %), where at least one of copper and silver is present. In one embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.25 wt. % Cu+Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.35 wt. % Cu+Ag. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.40 wt. % Cu+Ag. In another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.45 wt. % Cu+Ag. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.50 wt. % Cu+Ag.
When copper and/or silver are used, the alloys may include less zinc. For example, when the alloys include at least 0.05 wt. % Cu or at least 0.05 wt. % Ag, the alloys may include as low as 0.50 wt. % zinc. When copper and/or silver is not used, the alloys require higher zinc. For example, when the alloys include not greater than 0.04 wt. % Cu (i.e., Cu as an impurity) and not greater than 0.04 wt. % Ag (i.e., Ag as an impurity), the alloys include at least 0.75 wt. % zinc.
The new 5xxx-lithium aluminum alloy products may optionally contain up to 0.5 wt. % silicon (Si). In embodiments where silicon is used, the new 5xxx-lithium aluminum alloy products contain at least 0.05 wt. % Si. In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.35 wt. % Si. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.25 wt. % Si. In some embodiments silicon is present as an impurity, and in these embodiments the new 5xxx-lithium aluminum alloy products contain not greater than 0.04 wt. % Si.
The new 5xxx-lithium aluminum alloy products may optionally contain up to 1.0 wt. % manganese (Mn), In embodiments where manganese is used, the new 5xxx-lithium aluminum alloy products contain at least 0.05 wt. % Mn. In one embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.20 wt. % Mn. In another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.30 wt. % Mn. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain at least 0.40 wt. % Mn. In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.75 wt. % Mn. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.50 wt. % Mn. In some embodiments manganese is present as an impurity, and in these embodiments the new 5xxx-lithium aluminum alloy products contain not greater than 0.04 wt. % Mn.
The new 5xxx-lithium aluminum alloy products may include 0.05 to 0.50 wt. % of at least one grain structure control element selected from the group consisting of zirconium (Zr), scandium (Sc), chromium (Cr), vanadium (V) and/or hafnium (HO, and/or other rare earth elements, and such that the utilized grain structure control element(s) is/are maintained below maximum solubility. As used herein, “grain structure control element” means elements or compounds that are deliberate alloying additions with the goal of forming second phase particles, usually in the solid state, to control solid state grain structure changes during thermal processes, such as recovery and recrystallization. For purposes of the present patent application, grain structure control elements include Zr, Sc, Cr, V, Hf, other rare earth elements, and combinations thereof, but excludes Mn.
The amount of grain structure control material utilized in an alloy is generally dependent on the type of material utilized for grain structure control and/or the alloy production process. In one embodiment, the grain structure control element is Zr, and the alloy includes from 0.05 wt. % to 0.20 wt. % Zr. In another embodiment, the alloy includes from 0.05 wt. % to 0.15 wt. % Zr. In another embodiment, the alloy includes 0.07 to 0.14 wt. % Zr. In another embodiment, the alloy includes 0.08-0.13 wt. % Zr. In one embodiment, the aluminum alloy includes at least 0.07 wt. % Zr. In another embodiment, the aluminum alloy includes at least 0.08 wt. % Zr. In one embodiment, the aluminum alloy includes not greater than 0.18 wt. % Zr. In another embodiment, the aluminum alloy includes not greater than 0.15 wt. % Zr. In another embodiment, the aluminum alloy includes not greater than 0.14 wt. % Zr. In another embodiment, the aluminum alloy includes not greater than 0.13 wt. % Zr.
The new 5xxx-lithium aluminum alloy products may include up to 0.15 wt. % Ti cumulatively for ingot grain refining and/or other purposes. Grain refiners are inoculants or nuclei to seed new grains during solidification of the alloy. An example of a grain refiner is a 9.525 mm rod comprising 96% aluminum, 3% titanium (Ti) and 1% boron (B), where virtually all boron is present as finely dispersed TiB2 particles. During casting, the grain refining rod is fed in-line into the molten alloy flowing into the casting pit at a controlled rate. The amount of grain refiner included in the alloy is generally dependent on the type of material utilized for grain refining and the alloy production process. Examples of grain refiners include Ti combined with B (e.g., TiB2) or carbon (TiC), although other grain refiners, such as Al—Ti master alloys may be utilized. Generally, grain refiners are added in an amount ranging from 0.0003 wt. % to 0.005 wt % to the alloy, depending on the desired as-cast grain size. In addition, Ti may be separately added to the alloy in an amount up to 0.15 wt. % (cumulative), depending on product form, to increase the effectiveness of grain refiner, and typically in the range of 0.01 to 0.03 wt. % Ti. When Ti is included in the alloy, it is generally present in an amount of from 0.01 to 0.10 wt. %. In one embodiment, the aluminum alloy includes a grain refiner, and the grain refiner is at least one of TiB2 and TiC, where the wt. % of Ti in the alloy is from 0.01 to 0.06 wt. %, or from 0.01 to 0.03 wt. %.
The new 5xxx-lithium aluminum alloy products may include impurities of iron, copper, silver, silicon and/or manganese. Iron may be included in the alloy as an impurity in an amount of up to 0.25 wt. %. In one embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.15 wt. % Fe as an impurity. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.12 wt. % Fe as an impurity. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.10 wt. % Fe as an impurity. In another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.08 wt. % Fe as an impurity. In yet another embodiment, the new 5xxx-lithium aluminum alloy products contain not greater than 0.06 wt. % Fe as an impurity. As described above, copper, silver, silicon and/or manganese may be included in the alloy as an impurity, and when any of such elements are in the alloy as an impurity, the new 5xxx-lithium aluminum alloy products may include up to 0.04 wt. % each of any of such elements.
The new 5xxx-lithium aluminum alloy products generally contain low amounts of “other elements” (e.g., casting aids). As used herein, “other elements” means any other element of the periodic table except for aluminum and the above-described magnesium, lithium, zinc, copper, silver, silicon, manganese, titanium, grain structure control elements (i.e., Zr, Sc, Cr, V Hf, and other rare earth elements), and iron, as described above. In one embodiment, a new 5xxx-lithium aluminum alloy product contains not more than 0.10 wt. % each of any other element, with the total combined amount of these other elements not exceeding 0.35 wt. %. In another embodiment, each one of these other elements, individually, does not exceed 0.05 wt. % in a new 5xxx-lithium aluminum alloy product, and the total combined amount of these other elements does not exceed 0.15 wt. % in a 5xxx-lithium aluminum alloy product. In another embodiment, each one of these other elements, individually, does not exceed 0.03 wt. % in a 5xxx-lithium aluminum alloy product, and the total combined amount of these other elements does not exceed 0.10 wt. % in a 5xxx-lithium aluminum alloy product.
For the purposes of this patent application, the below chart identifies the difference between impurities and other elements.
a-1d are graphs illustrating mechanical properties of various Example 1 alloys.
a-1 is a graph illustrating the strength-toughness performance of various Example 2 alloys.
a-2 is a graph illustrating the strength-toughness performance of various Example 2 alloys.
Various 5xxx-lithium aluminum alloys were cast in book molds to make ingots approximately 3 inches thick. The alloy compositions are provided in Table 1, below.
Alloy 1 is based on conventional Russian alloy 01420 (the “1420” alloy). All of Alloys 1-8 contain not greater than 0.04 wt. % Si, not greater than 0.06 wt. % Fe, not greater than 0.04 wt. % Mn, and from 0.10 to 0.12 wt. % Zr, the balance being aluminum and other elements, the other elements not exceeding 0.05 wt. % each, and the combined amount of the other elements not totaling more than 0.15 wt. %.
After casting, all of the alloys were scalped, homogenized (preheated), and then hot rolled to final gauge of about 0.25 inch, after which the alloys were allowed to cool to room temperature. Next, the alloys were solution heat treated and quenched, after which the alloys were stretched about 3%, and then aged at 300° F. for various times, placing the alloys in a T8 temper. The mechanical properties of the aged samples were then tested in accordance with ASTM E8 and B557, the results of which are shown in Table 2, below, and illustrated in
Next, long transverse (LT) strength T-L plane strain fracture toughness tests were performed on the 24-hour aged alloy samples, the results of which are shown in Table 3, below, and illustrated in
As shown above, and in
Various 5xxx-lithium aluminum alloys were cast in book molds to make ingots, and then processed to a 0.25 inch (approx.) rolled product in the T8 temper per Example 1, above. The alloy compositions are provided in Table 4, below.
Unless otherwise noted below, all of Alloys 9-22 contain not greater than 0.04 wt. % Si, not greater than 0.06 wt. % Fe, not greater than 0.04 wt. % Mn, not greater than 0.02 wt. % Ti (added as a grain refiner), from 0.10 to 0.13 wt. % Zr, the balance being aluminum and other elements, the other elements not exceeding 0.05 wt. % each, and the combined amount of the other elements not totaling more than 0.15 wt. %.
The mechanical properties of the aged samples were then tested in accordance with ASTM E8 and B557, the results of which are shown in Tables 5-6, below (values averages of duplicate test specimens), and some of which are illustrated in
While various embodiments of the new technology described herein have been described in detail, it is apparent that modifications and adaptations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the presently disclosed technology.
| Number | Date | Country | |
|---|---|---|---|
| 61722571 | Nov 2012 | US |
