Patent Application
20240254595
6xxx aluminum alloys are aluminum alloys having silicon and magnesium to produce the precipitate magnesium silicide (Mg2Si). The alloy 6061 has been used in various applications for several decades. However, improving one or more properties of an aluminum alloy without degrading other properties is elusive. For automotive applications, a sheet having good formability prior to thermal treatment but with high strength after thermal treatment would be useful.
Broadly, the present patent application relates to new 6xxx aluminum alloys and methods for making the same. The new 6xxx aluminum alloys generally include from 0.95 to 1.25 wt. % Si, from 0.65 to 0.95 wt. % Mg, wherein (wt. % Mg)/(wt. % Si) is not greater than 0.99:1, from 0.50 to 0.75 wt. % Cu, from 0.02 to 0.40 wt. % Mn, from 0.03 to 0.26 wt. % Cr, wherein (wt. % Mn)+(wt. % Cr) is at least 0.22 wt. %, from 0.01 to 0.30 wt. % Fe, up to 0.25 wt. % Zn, up to 0.20 wt. % Zr, up to 0.20 wt. % V, and up to 0.15 wt. % Ti, the balance being aluminum, optional incidental elements and impurities. In one embodiment, the new 6xxx aluminum alloy is in the form of a rolled 6xxx aluminum alloy sheet product having a thickness of from 1.0 to 4.0 mm. Products made from the new 6xxx aluminum alloys may realize an improved combination of properties, such as an improved combination of two or more of strength, ductility (elongation), castability, fracture behavior and corrosion resistance. The new aluminum alloys may be used in a variety of applications, such as in automotive applications (e.g., as a sheet product).
As noted above, the 6xxx new aluminum alloys generally comprises (and in some instances consist essentially of, or consist of) from 0.95 to 1.25 wt. % Si, from 0.65 to 0.95 wt. % Mg, wherein (wt. % Mg)/(wt. % Si) is not greater than 0.99:1, from 0.50 to 0.75 wt. % Cu, from 0.02 to 0.40 wt. % Mn, from 0.03 to 0.26 wt. % Cr, wherein (wt. % Mn)+(wt. % Cr) is at least 0.22 wt. %, from 0.01 to 0.30 wt. % Fe, up to 0.25 wt. % Zn, up to 0.20 wt. % Zr, up to 0.20 wt. % V, and up to 0.15 wt. % Ti, the balance being aluminum, optional incidental elements and impurities. Using these specific amounts of elements may result in unique and useful products for use in, for instance, automotive applications, where high strength in combination with good ductility and corrosion resistance are required.
As noted above, the new 6xxx aluminum alloys generally include from 0.95 to 1.25 wt. % Si. Silicon may facilitate strength and improved castability. In one embodiment, a new aluminum alloy includes at least 1.0 wt. % Si. In another embodiment, a new aluminum alloy includes at least 1.05 wt. % Si. In yet another embodiment, a new aluminum alloy includes at least 1.10 wt. % Si. In one embodiment, a new aluminum alloy includes not greater than 1.20 wt. % Si.
As noted above, the new aluminum alloys generally include from 0.65 to 0.95 wt. % Mg. Magnesium may facilitate strength. In one embodiment, a new aluminum alloy includes at least 0.70 wt. % Mg. In another embodiment, a new aluminum alloy includes at least 0.75 wt. % Mg. In another embodiment, a new aluminum alloy includes at least 0.80 wt. % Mg. In one embodiment, a new aluminum alloy includes not greater than 0.90 wt. % Mg. In another embodiment, a new aluminum alloy includes not greater than 0.85 wt. % Mg.
As noted above, the weight ratio of Mg:Si is generally not greater than 0.99:1. The appropriate Mg:Si ratio may facilitate high strength, ductility and castability. In one embodiment, a weight ratio of Mg:Si is not greater than 0.90:1. In another embodiment, a weight ratio of Mg:Si is not greater than 0.85:1. In yet another embodiment, a weight ratio of Mg:Si is not greater than 0.80:1. In another embodiment, a weight ratio of Mg:Si is not greater than 0.75:1. In yet another embodiment, a weight ratio of Mg:Si is not greater than 0.70:1. In one embodiment, a weight ratio of Mg:Si is at least 0.50:1. In another embodiment, a weight ratio of Mg:Si is at least 0.55:1. In yet another embodiment, a weight ratio of Mg:Si is at least 0.60:1. In another embodiment, a weight ratio of Mg:Si is at least 0.65:1.
As noted above, the new aluminum alloys generally include from 0.50 to 0.75 wt. % Cu. Copper may facilitate, for instance, strength, natural aging response and/or formability. In one embodiment, a new aluminum alloy includes at least 0.55 wt. % Cu. In another embodiment, a new aluminum alloy includes at least 0.60 wt. % Cu. In yet another embodiment, a new aluminum alloy includes at least 0.65 wt. % Cu. In one embodiment, a new aluminum alloy includes not greater than 0.73 wt. % Cu. In another embodiment, a new aluminum alloy includes not greater than 0.70 wt. % Cu.
As noted above, the new aluminum alloys generally include from 0.02 to 0.40 wt. % Mn. Manganese may facilitate precipitation of dispersoids that at least partially assist in providing the proper grain structure. The amount of manganese in the alloy should be restricted such that large primary particles are avoided/restricted/limited during production of aluminum alloy products. In one embodiment, a new aluminum alloy includes at least 0.04 wt. % Mn. In another embodiment, a new aluminum alloy includes at least 0.05 wt. % Mn. In another embodiment, a new aluminum alloy includes at least 0.06 wt. % Mn. In yet another embodiment, a new aluminum alloy includes at least 0.08 wt. % Mn. In another embodiment, a new aluminum alloy includes at least 0.10 wt. % Mn. In yet another embodiment, a new aluminum alloy includes at least 0.15 wt. % Mn. In another embodiment, a new aluminum alloy includes at least 0.20 wt. % Mn. In one embodiment, a new aluminum alloy includes not greater than 0.35 wt. % Mn. In another embodiment, a new aluminum alloy includes not greater than 0.30 wt. % Mn.
As noted above, the new aluminum alloys generally include from 0.03 to 0.26 wt. % Cr. Chromium in combination with manganese may facilitate a unique distribution of dispersoid particles, which may facilitate achievement of high strength in combination with high three-point bending (fracture) properties. In one embodiment, a new aluminum alloy includes at least 0.03 wt. % Cr. In another embodiment, a new aluminum alloy includes at least 0.04 wt. % Cr. In yet another embodiment, a new aluminum alloy includes at least 0.06 wt. % Cr. In another embodiment, a new aluminum alloy includes at least 0.08 wt. % Cr. In another embodiment, a new aluminum alloy includes at least 0.10 wt. % Cr. In yet another embodiment, a new aluminum alloy includes at least 0.12 wt. % Cr. In another embodiment, a new aluminum alloy includes at least 0.14 wt. % Cr. In yet another embodiment, a new aluminum alloy includes at least 0.16 wt. % Cr. In another embodiment, a new aluminum alloy includes at least 0.18 wt. % Cr. In one embodiment, a new aluminum alloy includes not greater than 0.24 wt. % Cr. In another embodiment, a new aluminum alloy includes not greater than 0.22 wt. % Cr. In yet another embodiment, a new aluminum alloy includes not greater than 0.20 wt. % Cr.
As noted above, chromium in combination with manganese may facilitate a unique distribution of dispersoid particles, which may facilitate achievement of high strength in combination with high three-point bending (fracture) properties. Accordingly, the new aluminum alloys generally include at least 0.22 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.22 wt. %, as noted above. In one embodiment, a new aluminum alloy includes at least 0.24 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.24 wt. %. In another embodiment, a new aluminum alloy includes at least 0.25 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.25 wt. %. In yet another embodiment, a new aluminum alloy includes at least 0.26 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.26 wt. %. In another embodiment, a new aluminum alloy includes at least 0.27 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.27 wt. %. In yet another embodiment, a new aluminum alloy includes at least 0.28 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.28 wt. %. In another embodiment, a new aluminum alloy includes at least 0.29 wt. % (Mn+Cr), i.e., (wt. % Mn)+(wt. % Cr) is at least 0.29 wt. %.
As noted above, the new aluminum alloys generally include from 0.01 to 0.30 wt. % Fe. Iron may facilitate a proper grain structure and using more than 0.10 wt. % Fe iron may be cost effective. The amount of iron in the alloy should be restricted such that large primary particles are avoided/restricted/limited during production of aluminum alloy products. In one embodiment, a new aluminum alloy includes at least 0.05 wt. % Fe. In another embodiment, a new aluminum alloy includes at least 0.10 wt. % Fe. In yet another embodiment, a new aluminum alloy includes at least 0.12 wt. % Fe. In one embodiment, a new aluminum alloy includes not greater than 0.28 wt. % Fe. In another embodiment, a new aluminum alloy includes not greater than 0.26 wt. % Fc.
As noted above, the new aluminum alloys may include up to 0.25 wt. % Zn. In one embodiment, a new aluminum alloy includes not greater than 0.20 wt. % Zn. In another embodiment, a new aluminum alloy includes not greater than 0.15 wt. % Zn. In yet another embodiment, a new aluminum alloy includes not greater than 0.10 wt. % Zn. In another embodiment, a new aluminum alloy includes not greater than 0.08 wt. % Zn. In yet another embodiment, a new aluminum alloy includes not greater than 0.05 wt. % Zn. In another embodiment, a new aluminum alloy includes not greater than 0.03 wt. % Zn. In one embodiment, a new aluminum alloy includes at least 0.01 wt. % Zn.
As noted above, the new aluminum alloys include not greater than 0.20 wt. % Zr. Zirconium is less preferred than manganese and chromium, but still may be useful. The amount of zirconium in the alloy should be restricted such that large primary particles are avoided/restricted/limited during production of aluminum alloy products. In one embodiment, a new aluminum alloy includes not greater than 0.15 wt. % Zr. In another embodiment, a new aluminum alloy includes not greater than 0.10 wt. % Zr. In yet another embodiment, a new aluminum alloy includes not greater than 0.08 wt. % Zr. In another embodiment, a new aluminum alloy includes not greater than 0.05 wt. % Zr. In another embodiment, a new aluminum alloy includes not greater than 0.03 wt. % Zr. In yet another embodiment, a new aluminum alloy includes not greater than 0.01 wt. % Zr. In one embodiment, a new aluminum alloy includes at least 0.01 wt. % Zr (e.g., when Zr is added/used to the alloy for grain structure control). In another embodiment, a new aluminum alloy includes at least 0.05 wt. % Zr. In one embodiment, a new aluminum alloy includes from 0.07 to 0.15 wt. % Zr.
As noted above, the new aluminum alloys include not greater than 0.20 wt. % V. Vanadium is less preferred than manganese and chromium, but still may be useful. The amount of vanadium in the alloy should be restricted such that large primary particles are avoided/restricted/limited during production of aluminum alloy products. In one embodiment, a new aluminum alloy includes not greater than 0.15 wt. % V. In another embodiment, a new aluminum alloy includes not greater than 0.10 wt. % V. In yet another embodiment, a new aluminum alloy includes not greater than 0.08 wt. % V. In another embodiment, a new aluminum alloy includes not greater than 0.05 wt. % V. In another embodiment, a new aluminum alloy includes not greater than 0.03 wt. % V. In yet another embodiment, a new aluminum alloy includes not greater than 0.01 wt. % V. In one embodiment, a new aluminum alloy includes at least 0.01 wt. % V (e.g., when V is added/used to the alloy for grain structure control). In another embodiment, a new aluminum alloy includes at least 0.05 wt. % V. In one embodiment, a new aluminum alloy includes from 0.07 to 0.15 wt. % V.
As noted above, the new aluminum alloys include not greater than 0.25 wt. % Ti. Titanium may be used during casting for grain refinement. Higher levels of titanium may also facilitate corrosion resistance. The amount of titanium in the alloy should be restricted such that large primary particles are avoided/restricted/limited during production of alloy products. In one embodiment, a new aluminum alloy includes at least 0.005 wt. % Ti. In another embodiment, a new aluminum alloy includes at least 0.01 wt. % Ti. In yet another embodiment, a new aluminum alloy includes at least 0.02 wt. % Ti. In yet another embodiment, a new aluminum alloy includes at least 0.05 wt. % Ti. In one embodiment, a new a new aluminum alloy includes not greater than 0.20 wt. % Ti. In another embodiment, a new a new aluminum alloy includes not greater than 0.15 wt. % Ti. In another embodiment, a new aluminum alloy includes not greater than 0.12 wt. % Ti. In yet another embodiment, a new a new aluminum alloy includes not greater than 0.10 wt. % Ti. In another embodiment, a new a new aluminum alloy includes not greater than 0.08 wt. % Ti. In yet another embodiment, a new a new aluminum alloy includes not greater than 0.05 wt. % Ti. In another embodiment, a new a new aluminum alloy includes not greater than 0.03 wt. % Ti. In one embodiment, a new a new aluminum alloy includes from 0.005 to 0.10 wt. % Ti. In another embodiment, a new aluminum alloy includes from 0.01 to 0.05 wt. % Ti. In yet another embodiment, a new aluminum alloy includes from 0.01 to 0.03 wt. % Ti. The titanium may be in elemental form or in the form of compounds (e.g., TiB2 or TiC).
As noted above, the balance of the aluminum alloys is generally aluminum, optional incidental elements and impurities. As used herein, “incidental elements” means those elements or materials, other than the above listed elements, that may optionally be added to the alloy to assist in the production of the alloy. Examples of incidental elements include casting aids, such as grain refiners and deoxidizers. Optional incidental elements may be included in the alloy in a cumulative amount of up to 1.0 wt. %. As one non-limiting example, one or more incidental elements may be added to the alloy during casting to reduce or restrict (and is some instances eliminate) ingot cracking due to, for example, oxide fold, pit and oxide patches. These types of incidental elements are generally referred to herein as deoxidizers. Examples of some deoxidizers include Ca, Sr, and Be. When calcium (Ca) is included in the alloy, it is generally present in an amount of up to about 0.05 wt. %, or up to about 0.03 wt. %. In some embodiments, Ca is included in the alloy in an amount of about 0.001-0.03 wt. % or about 0.05 wt. %, such as 0.001-0.008 wt. % (or 10 to 80 ppm). Strontium (Sr) may be included in the alloy as a substitute for Ca (in whole or in part), and thus may be included in the alloy in the same or similar amounts as Ca. Traditionally, beryllium (Be) additions have helped to reduce the tendency of ingot cracking, though for environmental, health and safety reasons, some embodiments of the alloy are substantially Be-free. When Be is included in the alloy, it is generally present in an amount of up to about 20 ppm. Incidental elements may be present in minor amounts, or may be present in significant amounts, and may add desirable or other characteristics on their own without departing from the alloy described herein, so long as the alloy retains the desirable characteristics described herein. It is to be understood, however, that the scope of this disclosure should not/cannot be avoided through the mere addition of an element or elements in quantities that would not otherwise impact on the combinations of properties desired and attained herein.
The new aluminum alloys may contain low amounts of impurities. In one embodiment, a new aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the new aluminum alloy includes not greater than 0.05 wt. % of each of the impurities. In another embodiment, a new aluminum alloy includes not greater than 0.10 wt. %, in total, of the impurities, and wherein the new aluminum alloy includes not greater than 0.03 wt. % of each of the impurities.
The new aluminum alloys may be useful in a variety of product forms, including ingot or billet, wrought product forms (plate, forgings and extrusions), shape castings, additively manufactured products, and powder metallurgy products, for instance. For example, the new aluminum alloys may be processed into a variety of wrought forms, such as in rolled form (sheet, plate), as an extrusion, or as a forging, and in a variety of tempers. In this regard, the new aluminum alloys may be cast (e.g., direct chill cast or continuously cast), and then worked (hot and/or cold worked) into the appropriate product form (sheet, plate, extrusion, or forging). After working, the new aluminum alloys may be processed to one of a T temper, a W temper, O temper, or an F temper as per ANSI H35.1 (2009). In one embodiment, a new aluminum alloy is processed to a “T temper” (thermally treated). In this regard, the new aluminum alloys may be processed to any of a T1, T2, T3, T4, T5, T6, T7, T8, T9 or T10 temper as per ANSI H35.1 (2009). In one embodiment, the product is processed to a T43 temper. In another embodiment, the product is processed to a T6 temper. In other embodiments, a new aluminum alloy is processed to an “W temper” (solution heat treated). In another embodiment, no solution heat treatment is applied after working the aluminum alloy into the appropriate product form, and thus the new aluminum alloys may be processed to an “F temper” (as fabricated) or “O temper” (annealed).
In one embodiment, a new aluminum alloys is a sheet product. In one embodiment, the sheet product has a thickness of from 1.0 to 4.0 mm. In one embodiment, the sheet product is processed to a T4 temper. In one embodiment, the sheet product is processed to a T43 temper. In one embodiment, the sheet product is processed to a T4 or T43 temper and then paint baked (e.g., by heating at 180° C. for 20 minutes). In one embodiment, the sheet product is processed to a T4 or T43 temper, then paint baked, and then artificially aged (e.g., by heating at 180° C. for 8 hours). Such sheet products may be useful in automotive applications, as described in further detail below.
As used herein, the T43 temper refers to products that have been processed by pre-aging. For instance, a T43 temper product may be solution heat treated, then quenched to a suitable cooled temperature (e.g., below approximately 104.4° C. (220° F.)), then pre-aged at a suitable pre-aging temperature (e.g., between 60-115° C.), and then slowly cooled to room temperature (e.g., coil cooled or Newtonian cooling), after which the product is allowed to natural age for several days or weeks. To achieve the pre-aging temperature, the product may be cooled to the pre-aging temperature (after quench) or may be reheated to the pre-aging temperature. Multiple pre-aging times/temperatures may be used.
The new aluminum alloys may realize a unique microstructure. In one embodiment, a new aluminum alloy is at least 60% recrystallized, i.e., contains at least 60 vol. % recrystallized grains as determined in accordance with the Microstructure Assessment Procedure, described in the Definitions section, below. In another embodiment, a new aluminum alloy sheet is at least 70% recrystallized. In yet another embodiment, a new aluminum alloy sheet is at least 80% recrystallized. In another embodiment, a new aluminum alloy sheet is at least 90% recrystallized. For purposes of the present patent application, an aluminum alloy sheet product is “fully recrystallized” when it is determined to have at least 90 vol. % recrystallized grains.
In one embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 60 micrometers as determined in accordance with the Microstructure Assessment Procedure, described in the Definitions section, below. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 55 micrometers. In yet another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 50 micrometers. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 45 micrometers. In yet another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 40 micrometers. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 38 micrometers. In yet another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 36 micrometers. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 34 micrometers. In yet another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 32 micrometers. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of not greater than 30 micrometers. In one embodiment, a new aluminum alloy realizes an area weighted average grain size of at least 20 micrometers. In another embodiment, a new aluminum alloy realizes an area weighted average grain size of at least 25 micrometers. In yet another embodiment, a new aluminum alloy realizes an area weighted average grain size of at least 28 micrometers.
In one embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.5% as determined in accordance with the Microstructure Assessment Procedure, described in the Definitions section, below. In another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.55%. In yet another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.6%. In another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.65%. In yet another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.7%. In another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.75%. In yet another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.8%. In another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.85%. In yet another embodiment, a new aluminum alloy realizes a dispersoid area fraction of at least 0.9%. In one embodiment, a new aluminum alloy realizes a dispersoid area fraction of not greater than 1.1%. In another embodiment, a new aluminum alloy realizes a dispersoid area fraction of not greater than 1.0%.
In one embodiment, a new aluminum alloy realizes an f/r value at least 0.05 as determined in accordance with the Microstructure Assessment Procedure, described in the Definitions section, below. In another embodiment, a new aluminum alloy realizes an f/r value at least 0.06. In yet another embodiment, a new aluminum alloy realizes an f/r value at least 0.07. In another embodiment, a new aluminum alloy realizes an f/r value at least 0.08. In one embodiment, a new aluminum alloy realizes an f/r of not greater than 0.11. In another embodiment, a new aluminum alloy realizes an f/r of not greater than 0.10.
In one embodiment, a new aluminum alloy contains at least 10 vol. % cube texture as determined in accordance with the Microstructure Assessment Procedure, described in the Definitions section, below. In another embodiment, a new aluminum alloy contains at least 11 vol. % cube texture. In another embodiment, a new aluminum alloy contains at least 12 vol. % cube texture. In another embodiment, a new aluminum alloy contains at least 13 vol. % cube texture. In another embodiment, a new aluminum alloy contains at least 14 vol. % cube texture. In another embodiment, a new aluminum alloy contains at least 15 vol. % cube texture. In one embodiment, a new aluminum alloy contains not greater than 25 vol. % cube texture. In one embodiment, a new aluminum alloy contains not greater than 20 vol. % cube texture.
As noted above, the new aluminum alloys may realize an improved combination of properties. For instance, products made from the new 6xxx aluminum alloys may realize an improved combination of two or more of strength, ductility (elongation), castability, fracture behavior and corrosion resistance.
In one embodiment, the new aluminum alloy is a sheet product having a thickness of from 1.0 to 4.0 mm, and this aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 315 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 320 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In yet another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 325 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 330 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In yet another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 335 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 340 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In yet another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 345 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.). In another embodiment, the aluminum alloy sheet product realizes a tensile yield strength (LT) of at least 350 MPa in a T6 temper, wherein the artificial aging of the T6 temper is 30 minutes at 225° C. (437° F.).
In one approach, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing high three-point bend extensions in one or both of (a) the T4 temper and (b) the T6 pre-strained temper as per the “three-point bending test” described in the Definitions section, below. As noted below, all three-point bend testing is to be conducted at 2.0±0.05 mm. Thus, for an aluminum alloy sheet product having a thickness of from 1.0 to 1.94 mm or 2.06 to 4.0 mm, the bend extension for such a product is determined by reproducing the product at 2.0±0.05 mm, after which its three-point bend extension is measured. For purposes of three-point bending testing, the “T4” temper means the final gauge aluminum alloy sheet product is solution heat treated and quenched and then naturally aged for 1-month. For purposes of three-point bend testing, the “T6 temper” means the final gauge aluminum alloy sheet product is solution heat treated and quenched, then naturally aged for at least 2 weeks, and then artificially aged at 225° C. (437° F.) for 30 minutes.
In one embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 16.0 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 16.2 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 16.4 mm in the T4 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 16.6 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 16.8 mm in the T4 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 17.0 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 17.2 mm in the T4 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 17.4 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 17.6 mm in the T4 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 17.8 mm in the T4 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 18.0 mm in the T4 temper.
In one embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 10.0 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 10.5 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 11.0 mm in the T6 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 11.2 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 11.4 mm in the T6 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 11.6 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 11.8 mm in the T6 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 12.0 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 12.2 mm in the T6 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 12.4 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 12.6 mm in the T6 temper. In yet another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 12.8 mm in the T6 temper. In another embodiment, a new aluminum alloy sheet product has a thickness of 1.0 to 4.0 mm and is capable of realizing a three-point bend extension of at least 13.0 mm in the T6 temper.
In one approach, a new aluminum alloy is corrosion resistant, realizing a maximum depth of attack of not greater than 200 micrometers when tested in accordance with ASTM G110-92(2015) for 6 hours.
In one approach, a new aluminum alloy is filiform corrosion resistant, realizing at least comparable filiform corrosion resistance to AA6111 when tested in accordance with ASTM G85 A2 (e.g., within about 2 mm of the average length of filiform corrosion of AA6111 across three replicates).
The new aluminum alloy described herein may be used in a variety of applications, such as an automotive, rail, aerospace, or consumer electronics application. For example, a new aluminum alloy may be formed into an automotive part. Non-limiting examples of automotive parts include automotive bodies and automotive panels. Non-limiting examples of automotive panels may be outer panels, inner panels for use in car doors, car hoods, or car trunks (deck lids), among others. One example of an automotive body product may be a structural component, which are commonly sheet metal components of a car body (e.g., body-in-white) where additional strength is required to withstand crash requirements. In one embodiment, the new aluminum alloy is an enclosure for a battery, such as a battery used in an electric vehicle. The new aluminum alloys may also be used in other transportation applications, such as light or heavy trucks. Consumer electronic product applications include laptop computer cases, battery cases, among other stamped and formed products.
“Wrought aluminum alloy product” means an aluminum alloy product that is hot worked after casting, and includes rolled products (sheet or plate), forged products, and extruded products.
“Hot working” such as by hot rolling means working the aluminum alloy product at elevated temperature, and generally at least 121.1° C. (250° F.). Strain-hardening is restricted/avoided during hot working, which generally differentiates hot working from cold working.
“Cold working” such as by cold rolling means working the aluminum alloy product at temperatures that are not considered hot working temperatures, generally below about 121.1° C. (250° F.) (e.g., at ambient).
Temper definitions are per ANSI H35.1 (2009), entitled “American National Standard Alloy and Temper Designation Systems for Aluminum,” published by The Aluminum Association.
Strength and elongation are measured in accordance with ASTM E8/E8M-16a and B557-15.
“Three-point bending tests” (sometimes called 3-point bending tests) are measured in accordance with VDA 238-100, entitled, Plate bending test for metallic materials, Validation Rule, 1 Jun. 2017 (see https://www.vda.de/en/services/Publications/vda-238-100-plate-bending-test-for-metallic-materials.html), where the final gauge (thickness) of the sheet is 2.0±0.05 mm, the coupon is fixed in the test frame, and a punch radius of 0.2 mm is used, except the VDA test is modified as follows:
The following procedures and definitions apply to measuring microstructure features (e.g., percent recrystallization, dispersoid content and size, constituent content and size, texture) for products made in accordance with present patent application.
“Dispersoid area fraction”, f, is the area fraction covered by dispersoid particles divided by the total area examined in a two-dimensional cross section prepared by standard metallographic sample preparation methods.
“Dispersoid area %” is determined via the formula f×100.
“Dispersoid average diameter” is the average of all measured dispersoid diameters, di, where each diameter is an effective diameter calculated assuming each dispersoid area measured on a two-dimensional cross section is a circle of the effective diameter:
To measure the dispersoid area fraction, f, and dispersoid average diameters, backscattered electron images should be taken at 2000× on an Apreo S Field Emission Gun (Thermo Fisher Scientific, Waltham, MA, U.S.A) scanning electron microscope, or equivalent, to image dispersoids. The images should be taken using an accelerating voltage 5 kV. Beam current should be 3.2 nanoamps. Twenty images are to be collected from metallographically polished specimens for each alloy at both t/2 and the surface. Image analysis is to be used to quantify the images. The pixel size for quantifying dispersoids is 0.021 microns, and only particles containing at least 15 pixels but no more than 300 pixels are to be counted. Pixels are only counted if their gray scale value is 4 standard deviations above the mean pixel gray scale value across entire image. For each dispersoid particle, the number of pixels is converted to a particle area and to a particle effective diameter.
The quantity “f/r” is the dispersoid area fraction, f, divided by the dispersoid radius, which is determined by taking half of the dispersoid average diameter. This parameter is a measure of the pinning force on grain boundaries, also called Zener drag, (Ref.1), where higher values may be associated with finer grain size.
“Constituent area fraction”, cf, is the area fraction covered by constituent particles divided by the total area examined in a two-dimensional cross section prepared by standard metallographic sample preparation methods.
“Constituent area %” is determined via the formula cf×(times) 100.
“Constituent average diameter” is the average of all measured constituent diameters, di, where each diameter is an effective diameter calculated assuming each constituent area measured on a two-dimensional cross section is a circle of the effective diameter:
To measure the constituent area fraction, cf, and constituent average diameters, backscattered electron images should be taken at 500× on an Apreo S Field Emission Gun (Thermo Fisher Scientific, Waltham, MA, U.S.A) scanning electron microscope, or equivalent, to image dispersoids. The images should be taken using an accelerating voltage 5 kV. Beam current should be 3.2 nanoamps. Twenty images (minimum) are to be collected from metallographically polished specimens for each alloy at both t/2 and the surface. Image analysis is to be used to quantify the images. The pixel size for quantifying constituents is 0.083 microns, and only particles containing at least 23 pixels are to be counted. Pixels are only counted if their gray scale value is 4 standard deviations above the mean pixel gray scale value across entire image. For each constituent particle, the number of pixels is converted to a particle area and to a particle effective diameter.
“Percent recrystallized” and the like means the volume percent of a wrought aluminum alloy product having recrystallized grains. The amount of recrystallized grains is determined by EBSD (electron backscatter diffraction) analysis of a suitable number of SEM micrographs of the wrought aluminum alloy product, as per the Recrystallization Determination Procedure, below.
“Recrystallized grains” means those grains of a crystalline microstructure that meet the “first grain criteria”, defined below, and as measured using the OIM (Orientation Imaging Microscopy) sampling procedure, described below.
The OIM analysis is to be completed through the full thickness of the sheet sample on the L-ST plane, using the OIM sample procedure, below. The size of the sample to be analyzed will generally vary by gauge. Prior to measurement, the OIM samples are prepared by standard metallographic sample preparation methods. For example, the OIM samples are metallographically prepared and then polished (e.g., using 0.05 micron colloidal silica). The samples are then anodized in Barker's reagent, a diluted fluoroboric acid solution, for 90 seconds. The samples are then stripped using an aqueous phosphoric acid solution containing chromium trioxide, and then rinsed and dried.
The “OIM sample procedure” is as follows:
The term “grain” has the meaning defined in ASTM E112 § 3.2.2, i.e., “the area within the confines of the original (primary) boundary observed on the two-dimensional plane of-polish or that volume enclosed by the original (primary) boundary in the three-dimensional object”.
“Grain size” is calculated by the following equation:
“Area weighted average grain size” is calculated by the following equation:
“Texture” means a preferred orientation of at least some of the grains of a crystalline structure. Texture components resulting from production of aluminum alloy products may include one or more of copper, S texture, brass, cube, and Goss texture, to name a few. Each of these texture components is defined in Table A, below.
11
63
001
001
EBSD data for texture quantification are that same data that are generated as described above to determine “grain size” and “percent recrystallized.” The quantification of texture components present is done by the EBSD software, i.e. OIM Analysis Software, version 8.1.0 or equivalent. First step is to align the EBSD data from the L-ST plane into the more commonly used L-LT reference plane. Quantification of texture components present (Cube %, Goss %, Brass %, S %, Copper %) is to be determined as the number fraction of measured points assigned to a specific texture component. Points are assigned to a texture component if the misorientation angle deviates from the ideal orientation by less than 15 degrees. This number fraction is multiplied by 100 to find the percentage of each texture component in the sample.
Hot tearing susceptibility (HTS) is determined by running a Scheil calculation using Thermocal, version 2020 and the TCAL5 database or equivalent. The slope of a curve, defined by Temperature (y) versus Fraction Solid (x) in the range of Fraction Solid from 0.90 to 0.99, is the HTS (units of ° C.). Lower values of HTS are considered indications of lower tendency for hot cracking in ingot casting. See e.g., S. Kou, “A Simple Index for Predicting the Susceptibility to Solidification Cracking”, Welding Journal, December 2015, Vol. 94, p. 374-388, and X. Yan and J. Lin, “Prediction of Hot Tearing Tendency for Multicomponent Aluminum Alloys”, Met. Trans. B, Vol. 37B, December 2006, p. 913-918.
These and other aspects, advantages, and novel features of this new technology are set forth in part in the description that follows and will become apparent to those skilled in the art upon examination of the following description and figures, or may be learned by practicing one or more embodiments of the technology provided for by the present disclosure.
Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.
Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases “in one embodiment” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though they may. Furthermore, the phrases “in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, although they may. Thus, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.
In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references, unless the context clearly dictates otherwise. The meaning of “in” includes “in” and “on”, unless the context clearly dictates otherwise.
While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, unless the context clearly requires otherwise, the various steps may be carried out in any desired order, and any applicable steps may be added and/or eliminated.
One pilot-scale ingot of the aluminum alloy shown in Table 1 was homogenized and then conventionally scalped/peeled.
The homogenized ingot was then hot rolled to 3.531 mm (0.139 inch) followed by cold rolling (without any intermediate anneal) by 43% to a final gauge of 2.007 mm (0.079 inch). The final gauge material was then solution heat treated at 1040° F., water quenched, stretched for flatness, and then naturally aged for 7 days. The alloy was then either aged (i) aged at 437° F. (225° C.) for 30 minutes (“Age1”), or (ii) at 356° F. (180° C.) for 8 hours (“Age2”). The mechanical properties of the materials are shown in Table 2, below.
Fracture behavior was also evaluated using three-point bending tests (as defined in the Definitions section), the test results of which are also provided in Table 2, below. These tests are used to assess, inter alia, a material's (a) ability to be riveted without cracking and (b) behavior in crash situations. The tests were conducted relative to the transverse orientation (LT), and the reported values are based on the average of ten specimens used for each alloy tested. All properties are relative to the LT (long transverse) direction.
Conventional 6111 and 6013 alloys were produced similar to the above, i.e., cast as ingots, hot rolled to an intermediate gauge, cold rolled to final gauge, solution heat treated and then quenched, and then naturally aged for at least two weeks. The compositions of the alloys are shown in Table 3, below.
The 6111 and 6013 materials were naturally aged for at least 1.5 months and then aged per Age1. The mechanical properties were then tested, the results of which are shown in Table 4, below. All properties are relative to the LT (long transverse) direction.
As shown, the 6111 alloy is unable to achieve the strengths achieved by the invention alloy and the 6013 alloy is unable to achieve the high three-point bend properties achieved by the invention alloy.
The microstructure of the invention alloy and the 6111 and 6013 materials were also assessed. Specifically, grain size, texture, dispersoid fraction, and percent recrystallization were determined in accordance with the Microstructure Assessment Procedure, included herein. The invention alloy has a higher area fraction of dispersoids than both 6111 and 6013, and both the invention alloy and 6111 have finer dispersoids than 6013, as shown in Table 5. The invention alloys also have a notably higher f/r value than the 6013 and 6111 alloys. In the f/r ratio, f is the fraction of dispersoids (Area %/100) and r is the average dispersoid radius (Diameter/2). A higher f/r tends to result in greater grain boundary pinning, also called Zener drag, which will tend to promote fine grain size. While the invention alloy with high f/r actually realized a coarser grain size, this is likely because constituent particles tend to promote particle stimulated nucleation (PSN) recrystallization. All other things being equal, a material with more constituents is expected to realize a finer grain size, which is what is observed in Table 5. The finest grain size and the highest amount of constituent is observed in the 6111 alloy.
Texture measurements were also conducted in accordance with the Microstructure Assessment Procedure, the results of which are shown in Table 6. As shown, the invention alloy and 6111 both contain notably higher levels of the cube texture compared to 6013. Cube texture is a highly desirable component relative to formability and fracture behavior.
The hot tearing susceptibility (HTS) of the alloys was also calculated per the HTS procedure (above), the results of which are shown in Table 7, below.
As the data shows, the invention alloy realizes a very high combination of strength and fracture behavior, which may be due to its composition. The invention alloy also contains notably high levels of the cube texture. Further the invention alloy has lower hot tearing susceptibility than 6111, indicating improved castability.
Four production-scale ingots of the aluminum alloy shown in Table 8 were homogenized and then conventionally scalped/peeled.
Two of the homogenized ingots were hot rolled to 4.4 mm (0.172 inch) followed by cold rolling (without any intermediate anneal) by 43% to a final gauge of 2.5 mm (0.098 inch). The other two ingots were hot rolled 6.2 mm (0.244 inch) followed by cold rolling (without any intermediate anneal) by 43% to a final gauge of 3.5 mm (0.138 inch). The final gauge materials were then solution heat treated at about 510-548° C. (950-1019° F.) for times ranging from about 5 to 75 seconds.
Some of the materials were pre-aged after the quenching step to produce a T43 temper. Specifically, after quenching, those materials were pre-aged at about (a) 67 to 77° C. (153 to 170° F.) or (b) 77 to 83° C. (170-182° F.) for the 2.5 mm and 3.5 mm materials, respectively. Other materials were naturally aged after quenching to produce a T4 temper. Both the T4 and T43 tempers materials were naturally aged for about 1 month.
Next, some of the T4 materials were then either aged (i) aged at 437° F. (225° C.) for 30 minutes (“Age1”), or (ii) at 340° F. (180° C.) for 16 hours (“Age2”). The mechanical properties of these materials are shown in Table 9, below. Similarly, some of the T43 materials were either (i) aged at 185° C. (365° F.) for 20 minutes without any prestrain (“Age3”), or (ii) stretched 2% (pre-strained) and then aged at 185° C. (365° F.) for 20 minutes (“Age4”). The mechanical properties of the materials are shown in Table 10, below.
As shown, the alloys realized high strengths and elongations across the various conditions. Generally, higher strength was realized with higher solution heat treatment temperatures and/or longer solution heat treatment times.
For comparison purposes, mechanical properties of conventional plant produced 6111 and 6013 alloys were measured, the results of which are shown below in Table 11.
As shown, the 6111, T4 “Age 1” materials realized a TYS of 290 MPa whereas the invention alloy in the same condition realized TYS values as high as 336 MPa and 328 MPa for gauges of 2.5 mm and 3.5 mm, respectively. The invention alloy also realized much higher values for UTS than the commercial 6111 in the “Age1” condition.
As shown, the 6111, T43, “Age3” materials realized a TYS of 235 MPa whereas the invention alloy in the same condition realized values as high as 273 MPa and 268 MPa for gauges of 2.5 mm and 3.5 mm, respectively. Similarly, the 6111, T43, “Age 4” materials realized a TYS of 271 MPa whereas the invention alloy in the same condition realized values as high as 312 MPa and 301 MPa for gauges of 2.5 mm and 3.5 mm, respectively. The invention alloy also realized much higher values for UTS than the commercial 6111 in the “Age3” and “Age4” conditions.
As shown, the 6013-T6 (peak strength) materials realized a TYS of 349 MPa and a UTS of 387 MPa. The invention alloy, however, had much higher total elongation at 14.9% compared to a value of 10.8% for the 6013 product. Further, it is expected that the 6013 alloy will realize poor filiform corrosion (per ASTM G85 A2) making it unsuitable for automotive applications. The poor filiform corrosion of 6013 may be at least due to its copper content, which is typically greater than 0.8 wt. %.
While various embodiments of the present disclosure 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 present disclosure.
This application is a continuation of International Patent Application no. PCT/US2022/037405, filed Jul. 22, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63/224,770 entitled “NEW 6XXX ALUMINUM ALLOYS” filed Jul. 22, 2021, each of which are incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63224770 | Jul 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2022/037405 | Jul 2022 | WO |
| Child | 18417434 | US |
