6XXX ALUMINUM ALLOYS

Abstract

New 6xxx aluminum alloy products and methods and systems of making the same are disclosed. A method may include heating a billet of a 6xxx aluminum alloy to a preheat temperature, holding the billet at the preheat temperature for a time sufficient to dissolve at least some precipitate hardening phases of the billet, extruding the billet into an extruded product wherein, during the extruding, both the billet and the extruded product are maintained at or above the preheat temperature, discharging the extruded product from the extrusion apparatus while maintaining the extruded product within 100° F. of a solvus temperature of the 6xxx aluminum alloy, and moving the extruded product from the heating shroud to a quenching apparatus.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US2021/057580, filed Nov. 1, 2021, which claims the benefit of U.S. Provisional Patent Application No. 63/108,077, filed Oct. 30, 2020, entitled “IMPROVED 6XXX ALUMINUM ALLOYS,” each of which is incorporated herein by reference in its entirety.

BACKGROUND

Press-quenching of extruded 6xxx aluminum alloy products facilitates rapid production of such extruded products without the need for a separate solution heat treatment step following the extrusion process. As commonly-owned U.S. Pat. No. 7,422,645 explains, a press quenched product is one that has been rapidly cooled from an elevated deformation extrusion temperature by immersion in a liquid bath, such as oil or water, so as to withdraw heat rapidly from the product. The purpose of quenching is to suppress a phase transformation so as to obtain increased hardness, or other desirable properties. When an aluminum alloy product, such as a billet or ingot, is extruded, it is first reheated to and held at a temperature in the alloy above the solubility temperature in the precipitated phases in the aluminum matrix, for instance the solubility temperature for the magnesium (Mg)-silicon (Si) phases in a billet made of an Al—Mg—Si-alloy, until the phases are dissolved. The product is then quickly cooled or quenched to the desired extrusion temperature to prevent new precipitation of these phases in the alloy structure, and then extruded.

SUMMARY OF THE DISCLOSURE

Broadly, the present patent application relates to new press-quenched 6xxx aluminum alloy products and methods and systems for producing the same. The new methods and systems may facilitate, for instance, production of 6xxx aluminum alloy products having an improved combination of properties, such an improved combination of strength and ductility (elongation).

I. Systems and Methods

Referring now to FIG. 1, one method (100) of producing an extruded 6xxx aluminum alloy product is illustrated. In the illustrated embodiment, the method includes homogenizing (110) a billet of a 6xxx aluminum alloy, preheating (120) the billet, extruding (130) the billet in an extrusion apparatus, discharging (140) the extruded product from extrusion apparatus while maintaining (145) the extruded product at an appropriate pre-quench temperature, quenching (150) the extruded product, and then artificially aging (160) the extruded product. These steps are described in further detail below. One embodiment of a system (200) for completing method (100) is illustrated in FIG. 2. FIGS. 1-2 are used below, in a non-limiting fashion, to illustrate embodiments of the new inventive methods and systems.

The homogenizing step (110) is optional and generally includes heating a billet of the 6xxx aluminum alloy to one or more temperatures for one or more times to homogenize the as-cast structure. After the homogenizing step, the billet is generally cooled to room temperature and stored until it is to be extruded. For purposes of the present application, and for ease of reference, the term “billet” encompassed both round billet and rectangular ingot.

When it is time for the billet to be extruded, the preheating step (120), the extruding step (130), the discharging step (140) and the quenching step (150) are completed in order and without any intervening steps. This is to ensure an appropriate microstructure is achieved in the final product.

Specifically, the billet is preheated (120) to a preheat temperature and then held at this temperature for a time sufficient to dissolve at least some precipitate phases of the billet. As shown in FIG. 2, the preheating step (120) may be completed in a furnace (220). In one embodiment, the preheat temperature is at least 50% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. For instance, if the solvus temperature is 962° F., “at least 50% of the solvus temperature” is ≥481° F., so the preheat temperature would be ≥481° F. but below the incipient melting point of the 6xxx aluminum alloy.

As used herein, “solvus temperature” means the lowest temperature at which all of the following precipitate phases would completely be dissolved at equilibrium in the 6xxx aluminum alloy billet and without incipient melting of the 6xxx aluminum alloy billet:

• • Mg₂Si
  • Q-phase (Al₅Cu₂Mg₈Si₆)
  • Theta (θ) (Al₂Cu)
    For purposes of clarity, the term “solvus temperature” only includes the above phases for 6xxx aluminum alloys, and does not include any other dissolvable precipitate phases, such as Mg₂Sn and Bi₂Mg₃.

In one embodiment, the preheat temperature is at least 60% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In another embodiment, the preheat temperature is at least 70% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In yet another embodiment, the preheat temperature is at least 80% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In another embodiment, the preheat temperature is at least 90% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In yet another embodiment, the preheat temperature is at least 95% of the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In another embodiment, the preheat temperature is at or above the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In yet another embodiment, the preheat temperature is at least 5° F. above the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In another embodiment, the preheat temperature is at least 10° F. above the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In yet another embodiment, the preheat temperature is at least 15° F. above the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. In another embodiment, the preheat temperature is at least 20° F. above the solvus temperature of the 6xxx aluminum alloy but below the incipient melting point of the 6xxx aluminum alloy. Generally, when high mechanical properties are desired, the preheat temperature should be at least 90-100% of the solvus temperature, or higher.

The preheating step (120) also includes holding the billet at the preheat temperature for a period of time sufficient to dissolve at least some precipitate phases of the 6xxx aluminum alloy. The holding time may depend on, for instance, the size of the billet and the desired end properties. In one embodiment, the preheating step (120) includes holding the billet at the preheat temperature for a period of time sufficient to dissolve the majority of, or even all of, the precipitate phases of the 6xxx aluminum alloy. In one embodiment, the holding time is at least 1 minute. In another embodiment, the holding time is at least 5 minutes. In yet another embodiment, the holding time is at least 10 minutes. In another embodiment, the holding time is at least 20 minutes. In yet another embodiment, the holding time is at least 30 minutes. In another embodiment, the holding time is at least 40 minutes. In yet another embodiment, the holding time is at least 50 minutes, or more. Generally, when high mechanical properties are desired, the holding time at the preheat temperature should be sufficient to dissolve the majority of, or even all of, the precipitate phases of the 6xxx aluminum alloy. As may be appreciated, a plurality of preheat temperatures and a corresponding plurality of preheat holding times may be employed.

In one embodiment, the preheat temperature is at least 950° F. In another embodiment, the preheat temperature is at least 960° F. In yet another embodiment, the preheat temperature is at least 970° F. In another embodiment, the preheat temperature is at least 975° F. In any of the above embodiments, the preheat holding time may be 40-60 minutes (e.g., with a fifteen-inch diameter billet).

Non-limiting embodiments of a preheating step are shown in FIGS. 3a-3b. As shown, the billet is heated (a) from room temperature (T_room) to a preheat temperature, which, in this case is the metallurgical required temperature (T_MR) or the temperature required to achieve high mechanical properties. As shown, the metallurgical required temperature (T_MR) exceeds the solvus temperature (T_solvus). As also shown, the preheat holding time, referred to as t_mr and shown as (b) in FIGS. 3a-3b, is generally long so as to dissolve the majority of, or even all of, the precipitate phases of the 6xxx aluminum alloy.

As further shown in FIGS. 3a-3b, the preheat temperature (T_MR) is below the incipient melting temperature or T_solidus, i.e., no eutectic melting should occur. As shown in FIGS. 3a-3b, the extrusion process (described in further detail below) may result in further heating of the product. This further heating generally should avoid the product exceeding the incipient melting temperature or T_solidus of the 6xxx aluminum alloy. Thus, the preheat temperature is generally at least 10° F. below the incipient melting temperature of the 6xxx aluminum alloy billet. In one embodiment, the preheat temperature is at least 20° F. below the incipient melting temperature of the 6xxx aluminum alloy billet. In another embodiment, the preheat temperature is at least 30° F. below the incipient melting temperature of the 6xxx aluminum alloy billet. In yet another embodiment, the preheat temperature is at least 40° F. below the incipient melting temperature of the 6xxx aluminum alloy billet. In another embodiment, the preheat temperature is at least 50° F. below the incipient melting temperature of the 6xxx aluminum alloy billet.

Referring back to FIGS. 1-2, after the preheating step (120), the preheated billet is immediately transferred to an extrusion apparatus where the billet is extruded (130). As shown in FIG. 2, the term “immediately transferred to an extrusion press” means that the surface of the billet realizes a temperature drop of not greater than 100° F. from the time it exits the preheating apparatus (e.g., furnace 220) to the time it enters the extrusion apparatus (e.g., extrusion press 230). This is also shown in FIGS. 3a-3b, where the transferring step (c) shows a very low temperature drop. The low temperature drop is generally completed by utilizing a small distance between the preheating apparatus and the extrusion apparatus in combination with appropriate scheduling of billet flow through the various apparatus of the system (200). Maintaining a low temperature drop from the preheat apparatus to the extrusion apparatus may facilitate realization of the desired microstructure and properties. Due to the high preheat temperatures employed with the preheating step (120), an extrusion press (230) can rapidly and efficiently extrude the billet into the end product during the extrusion step (130), which increases productivity.

In one embodiment, the billet realizes a temperature drop of not greater than 75° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In another embodiment, the billet realizes a temperature drop of not greater than 50° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In yet another embodiment, the billet realizes a temperature drop of not greater than 40° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In another embodiment, the billet realizes a temperature drop of not greater than 30° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In yet another embodiment, the billet realizes a temperature drop of not greater than 20° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In another embodiment, the billet realizes a temperature drop of not greater than 10° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In yet another embodiment, the billet realizes a temperature drop of not greater than 5° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus. In another embodiment, the billet realizes a temperature drop of not greater than 2° F. from the time it exits the preheating apparatus to the time it enters the extrusion apparatus.

The extruding step (130) generally comprises extruding the billet into an appropriate suitable end product, such as a bar, rod, tube or a complex shape via an extrusion apparatus, such as an extrusion press (230). The extruding step may be accomplished by direct or indirect extrusion. In one approach, the extruding step (130) comprises maintaining the billet and the extruded product at or above the preheat temperature. In one embodiment, the extruding step comprises heating the extruded product during the extruding step (130). Extrusion heating may result, for instance, due to friction imparted on the billet by the extrusion apparatus (e.g., extrusion press (230)) during the extruding step). For instance, as, shown in FIGS. 3a-3b, during the extrusion step (d) the temperature of the product increases relative to the preheat temperature (T_MR), finally realizing an extrusion exit temperature (EET). The extrusion exit temperature (EET) is the temperature of the extruded product immediately after it exits the extrusion apparatus. In one embodiment, the extrusion exit temperature (EET) is at least 10° F. higher than the preheat temperature. In another embodiment, the extrusion exit temperature (EET) is at least 20° F. higher than the preheat temperature. In yet another embodiment, the extrusion exit temperature (EET) is at least 30° F. higher than the preheat temperature. In another embodiment, the extrusion exit temperature (EET) is at least 40° F. higher than the preheat temperature. In yet another embodiment, the extrusion exit temperature (EET) is at least 50° F. higher than the preheat temperature.

Next, the extruded product is discharged from the extrusion apparatus (140). As part of the discharging step (140), the temperature of the extruded product is maintained (145) close to that of the extrusion exit temperature (EET) until the product can be quenched (150) by water or another suitable quenching medium. This is also shown in FIGS. 3a-3b, where the temperature drop (e) from the extruding step (d) to the quenching step (f) is low. In one approach, the temperature of the extruded product is maintained within 100° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In one embodiment, the temperature of the extruded product is maintained within 75° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In another embodiment, the temperature of the extruded product is maintained within 50° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In yet another embodiment, the temperature of the extruded product is maintained within 40° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In another embodiment, the temperature of the extruded product is maintained within 30° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In yet another embodiment, the temperature of the extruded product is maintained within 20° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In another embodiment, the temperature of the extruded product is maintained within 10° F. of the extrusion exit temperature (EET) until the quenching step (150) commences. In yet another embodiment, the temperature of the extruded product is maintained within 5° F. of the extrusion exit temperature (EET) until the quenching step (150) commences.

In one embodiment, the maintaining step (145) comprises maintaining the extruded product at or above the solvus temperature until the quenching step (150) commences. In one embodiment, the maintaining step (145) comprises maintaining the extruded product at least 5° F. above the solvus temperature until the quench commences. In another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 10° F. above the solvus temperature until the quench commences. In yet another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 15° F. above the solvus temperature until the quench commences. In another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 20° F. above the solvus temperature until the quench commences. In yet another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 25° F. above the solvus temperature until the quench commences. In another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 30° F. above the solvus temperature until the quench commences. In yet another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 35° F. above the solvus temperature until the quench commences. In another embodiment, the maintaining step (145) comprises maintaining the extruded product at least 40° F. above the solvus temperature until the quench commences.

As shown in FIG. 2, an exit shroud (240) may be used to facilitate the maintaining step (145). The exit shroud (240) may be directly adjacent to the outlet of the extrusion apparatus (230) so as to facilitate the maintaining step (145). For instance, and referring now to FIG. 4, as the billet is extruded through an extrusion die, it is discharged to an extrusion press tunnel. Within the extrusion press tunnel may be located one or more passive and/or active heating apparatus. Examples of a passive heating apparatus include a surrounding shield designed to reflect heat radiated from the extruded product back towards the product. The surrounding shield may fully encompass (e.g., encircle) the extruded product or may partially surround the extruded product. In one embodiment, a heat shield comprises a material adapted to reflect heat radiated from the extruded product, such as a metal (e.g., stainless steel). Insulating materials such as supported fiberglass, ceramic fiber, and mineral wool blankets, for instance, may also or alternatively be used to maintain the extruded product temperature within the needed tolerance. Other apparatus useful for retaining heat include hot air curtains or physical curtains, such as chain mail.

In one embodiment, the exit shroud (240), which may be in the form of an extrusion press tunnel (FIG. 4), may include one or more active heating apparatus. Examples of active heating apparatus include radiative heat lamps, hot air fans, and resistance heaters, among others. Both active and passive heating apparatus/materials may be used.

Referring back to FIGS. 1-2, after the discharging step (140), the extruded product is immediately moved to a quenching apparatus (250), such as an apparatus including a stationary or moving water spray and/or a water bath, so as to rapidly quench the product to a suitable low temperature, such as room temperature. This is illustrated, for instance, in FIGS. 3a-3b, where the quenching step (f) rapidly quenches the extruded product received from the exit shroud to T_room.

As noted above, the quenching step (150) occurs immediately after the discharging step (140). The quenching step may be begin by contacting exposed portions of the extruded product as they exit the exit shroud (240), i.e., when the exposed portions are those no longer contained within the exit shroud (240). In one embodiment, the exposed portions of the extruded product are within 50° F. of the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are within 40° F. of the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are within 30° F. of the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are within 20° F. of the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are within 10° F. of the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are at or above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are at least 5° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are at least 10° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are at least 15° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are at least 20° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are at least 25° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are at least 30° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are at least 35° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In another embodiment, the exposed portions of the extruded product are at least 40° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product. In yet another embodiment, the exposed portions of the extruded product are at least 45° F. above the solvus temperature when the quenching medium initially contacts the discharged extruded product.

As noted above, the quenching step (150) may begin by contacting the exposed portions of the extruded product as they exit the exit shroud (240). As shown in FIG. 4, this may be accomplished, for instance, by using a water spray located immediately adjacent the outlet of the exit shroud, which may be in the form of an extrusion press tunnel. In one embodiment, the water contacts the exposed portions of the extrusion within 60 seconds of their exit from the exit shroud. In another embodiment, the water contacts the exposed portions of the extrusion within 45 seconds of their exit from the exit shroud. In yet another embodiment, the water contacts the exposed portions of the extrusion within 30 seconds of their exit from the exit shroud. In another embodiment, the water contacts the exposed portions of the extrusion within 20 seconds of their exit from the exit shroud. In yet another embodiment, the water contacts the exposed portions of the extrusion within 10 seconds of their exit from the exit shroud. In another embodiment, the water contacts the exposed portions of the extrusion within 8 seconds of their exit from the exit shroud. In yet another embodiment, the water contacts the exposed portions of the extrusion within 5 seconds of their exit from the exit shroud.

With continued reference to FIG. 4, the quenching apparatus may include a quench bath, such as an immersion bath (stationary water cooling). The quench bath may be located downstream of any quenching water spray. The use of the water bath may facilitate further rapid cooling of the extruded product (extrudate) to an appropriate temperature (e.g., quenching to room temperature, as shown in FIGS. 3a-3b (T_room)). In one embodiment, the relative motion between the extrudates and the water creates a shear flow on the surfaces of the extrudate, which increases cooling effectiveness. In one embodiment, the water bath facilitates a quench rate of at least 1° F./second. The water bath quench rate is measured by determining the temperature of the extruded prior to entering the water bath and then measuring the time it takes for the extruded product to reach a temperature of 125° F. In another embodiment, the water bath facilitates a quench rate of at least 5° F./second. In yet another embodiment, the water bath facilitates a quench rate of at least 10° F./second. In another embodiment, the water bath facilitates a quench rate of at least 20° F./second. In yet another embodiment, the water bath facilitates a quench rate of at least 30° F./second.

Although water is used herein to describe the inventive systems/methods, any suitable quenching medium may be used, which quenching medium is preferably in liquid form.

As shown in the Examples section, below, steps (120)-(150) and their associated system components (220)-(250), described above, facilitate the production of press-quenched 6xxx aluminum alloy product having improved microstructures and, hence, an improved combination of properties. As illustrated in FIGS. 3a-3b, such press-quenched products may be immediately aged (g) and/or further cold worked (h) (e.g., drawn) and without any additional solution heat treatment steps. For instance, after quenching, the extruded products may be processed to any of a T6, T8 or T9 temper, as illustrated in FIGS. 3a-3b. Such T6, T8 or T9 tempered products generally realize an improved combination of properties due to the press-quenching methods and apparatus described herein.

It should be appreciated that the maintaining step (145) is optional. For instance, in one embodiment, an extruded product may be discharged (140) from the extrusion apparatus but without the use of an exit shroud (240). In such embodiments, the extruded product should be quenched (150) as soon as possible after the discharging step (140) when high tensile properties are required.

II. Compositions

As noted above, the new systems and methods may be applied to any 6xxx aluminum alloy that is suited for extrusion. In one embodiment, the 6xxx aluminum alloy includes from 0.2 to 2.0 wt. % Si, from 0.2 to 1.5 wt. % Mg, from 0.07 to 1.0 wt. % Mn, up to 1.5 wt. % Bi, up to 1.5 wt. % Sn, up to 1.0 wt. % Cu, up to 1.0 wt. % Zn, up to 0.7 wt. % Pb, up to 0.7 wt. % Fe, up to 0.35 wt. % Cr, up to 0.35 wt. % V, up to 0.25 wt. % Zr, and up to 0.20 wt. % Ti, the balance being 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 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 in 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 6xxx aluminum alloys may contain low amounts of impurities. In one embodiment, a new 6xxx aluminum alloy includes not greater than 0.15 wt. %, in total, of the impurities, and wherein the aluminum alloy includes not greater than 0.05 wt. % of each of the impurities. In another embodiment, a new 6xxx aluminum alloy includes not greater than 0.10 wt. %, in total, of the impurities, and wherein the aluminum alloy includes not greater than 0.03 wt. % of each of the impurities.

In one embodiment, the 6xxx aluminum alloy is one of a 6026LF, 6020, 6262A and a 6061 aluminum alloy. The compositions of the conventional 6020, 6262A, and 6061 alloys described herein are per the Aluminum Association document entitled “International Alloy Designations and Chemical Composition Limits for Wrought Aluminum and Wrought Aluminum Alloys” (2015). The “6026LF” alloy is a lead-free version of the 6026 alloy, and includes 0.60-1.40 wt. % Si, ≤0.70 wt. % Fe, 0.20-0.50 wt. % Cu, 0.20-1.00 wt. % Mn, 0.60-1.20 wt. % Mg, ≤0.30 wt. % Cr, ≤0.30 wt. % Zn, ≤0.20 wt. % Ti, ≤0.05 wt. % Sn, ≤0.05 wt. % Pb, and 0.50-1.50 wt. % Bi, the balance being aluminum and impurities.

Although the present methods and systems have been described relative to 6xxx aluminum alloys, it is anticipated that such methods and systems could also be applied to other heat treatable (precipitation hardenable) aluminum alloys, such a 2xxx or a 7xxx aluminum alloy. Thus, the present patent application is also expressly directed to methods and systems of extruding 2xxx aluminum alloys as well as methods and systems of extruding 7xxx aluminum alloys. In the case of 2xxx aluminum alloys, applicable solvus temperatures may include those associated with the theta (θ), omega (Ω) and/or S phases, among others. In the case of 7xxx aluminum alloys, applicable solvus temperatures include those associated with the eta (η) phase, among others.

III. Microstructure

As noted above, the 6xxx aluminum alloy products may realize inventive microstructure. In one approach, a 6xxx aluminum alloy realizes an unrecrystallized microstructure as measured from T/10 to 9T/10 of the 6xxx extruded product wherein the unrecrystallized microstructure comprises at least 50 vol. % unrecrystallized grains. In one embodiment, at least 60% of the unrecrystallized grains are fibrous grains. Fibrous grains are those having an aspect ratio (grain length/diameter) of at least 5:1. In one embodiment, the average grain size of the unrecrystallized microstructure is not greater than 200 microns.

In another approach, the 6xxx extruded product realizes a recrystallized microstructure as measured from T/10 to 9T/10 of the 6xxx extruded product wherein the recrystallized microstructure comprises at least 50 vol. % recrystallized grains. In one embodiment, at least 60% of the recrystallized grains are equiaxed grains having as aspect ratio of less than 5:1 (L:LT) (e.g., from 1:1 to 4.9:1; or from 1.5:1 to 4.9:1). In one embodiment, the average grain size of the recrystallized microstructure is not greater than 200 microns.

IV. Properties

As noted above, the new 6xxx aluminum alloys may realize an improved combination of properties, such as an improved combination of strength and elongation.

In one embodiment, the new 6xxx aluminum alloy is a new 6026LF extruded product i.e., made by the inventive methods and/or systems described herein. The new 6026LF extruded product may realize at least 5% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6026LF product. In one embodiment, a new 6026LF extruded product may realize at least 10% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6026LF product of the same product form, size and temper. In another embodiment, a new 6026LF extruded product may realize at least 15% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6026LF product of the same product form, size and temper. In yet another embodiment, a new 6026LF extruded product may realize at least 20% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6026LF product of the same product form, size and temper. In one embodiment, a new 6026LF extruded product realizes a tensile yield strength (typical)(L) of at least at least 54 ksi, or at least 55 ksi, or at least 56 ksi, or at least 57 ksi, or more.

In one embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation (longitudinal or L) of at least 3%. In another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 4% (L). In yet another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 5% (L). In another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 6% (L). In yet another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 7% (L). In another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 8% (L). In another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 9% (L). In yet another embodiment, the new 6026LF extruded product may realize the above strength values in combination with an elongation of at least 10% (L).

In one approach, a new extruded 6026LF aluminum alloy product realizes at least one of (a) 17 vol. % cube (ED) texture and (b) a maximum ODF [001] intensity of at least 9.7, as measured per the EBSD Sample Procedure, below. In one embodiment, the extruded 6026LF aluminum alloy realizes at least 18 vol. % cube (ED) texture, or at least 19 vol. % cube (ED) texture. In one embodiment, the extruded 6026LF aluminum alloy product realizes a maximum ODF [001] intensity of at least 9.8, or at least 10.0, or at least 10.2, or at least 10.4, or at least 10.6, or at least 10.8, or at least 11.0, or at least 11.2.

In one embodiment, the new 6xxx aluminum alloy is a new 6020 extruded product i.e., made by the inventive methods and/or systems described herein. The new 6020 extruded product may realize at least 5% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6020 product, e.g., a 6020 extruded product made in accordance with U.S. Pat. No. 7,422,645, of the same product form, size and temper. In one embodiment, a new 6020 extruded product may realize at least 10% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6020 product of the same product form, size and temper. In another embodiment, a new 6020 extruded product may realize at least 15% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6020 product of the same product form, size and temper. In yet another embodiment, a new 6020 extruded product may realize at least 20% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6020 product of the same product form, size and temper. In one embodiment, a new extruded 6020 product realizes a tensile yield strength (typical) (L) of at least 34 ksi, or at least 35 ksi, or at least 36 ksi, or at least 37 ksi, or at least 38 ksi, or at least 39 ksi, or at least 40 ksi, or at least 41 ksi, or at least 42 ksi, or at least 43 ksi, or at least 44 ksi, or at least 45 ksi. In one embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation (longitudinal or L) of at least 8%. In another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 9% (L). In yet another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 10% (L). In another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 11% (L). In yet another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 12% (L). In another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 13% (L). In yet another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 14% (L). In another embodiment, the new 6020 extruded product may realize the above strength values in combination with an elongation of at least 15% (L).

In one approach, a new extruded 6020 aluminum alloy product realizes at least one of (a) 17 vol. % cube (ED) texture and (b) a maximum ODF [001] intensity of at least 3.6, as measured per the EBSD Sample Procedure, below. In one embodiment, a new extruded 6020 aluminum alloy product realizes at least 18 vol. % cube (ED) texture, or at least 19 vol. % cube (ED) texture, or at least 20 vol. % cube (ED) texture, or at least 21 vol. % cube (ED) texture, at least 22 vol. % cube (ED) texture, or at least 23 vol. % cube (ED) texture, at least 24 vol. % cube (ED) texture, or at least 25 vol. % cube (ED) texture, at least 26 vol. % cube (ED) texture, or at least 27 vol. % cube (ED) texture, or more. In one embodiment, a new 6020 extruded aluminum alloy product realizes a maximum ODF [001] intensity of at least 3.8, or at least 4.0, or at least 4.2, or at least 4.4, or at least 4.6, or at least 4.8, or at least 5.0, or at least 5.2, or at least 5.4, or at least 5.6, or at least 5.8, or at least 6.0, or at least 6.2, or at least 6.4, or at least 6.6, or at least 6.8, or at least 7.0.

In one embodiment, the new 6xxx aluminum alloy is a new 6262A extruded product i.e., made by the inventive methods and/or systems described herein. The new 6262A extruded product may realize at least 5% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6262A product. In one embodiment, a new 6262A extruded product may realize at least 10% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6262A product of the same product form, size and temper. In another embodiment, a new 6262A extruded product may realize at least 15% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6262A product of the same product form, size and temper. In yet another embodiment, a new 6262A extruded product may realize at least 20% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6262A product of the same product form, size and temper. In one embodiment, a new 6262A extruded product realizes a tensile yield strength (typical) (L) of at least 37 ksi, or at least 38 ksi, or at least 39 ksi, or at least 40 ksi, or at least 41 ksi, or at least 42 ksi, or at least 43 ksi, or at least 44 ksi, or at least 45 ksi, or at least 46 ksi, or at least 47 ksi, or at least 48 ksi, or at least 49 ksi, or at least 50 ksi, or at least 51 ksi, or at least 52 ksi, or at least 53 ksi, or at least 54 ksi. In one embodiment, the new 6262A extruded product may realize the above strength values in combination with an elongation (longitudinal or L) of at least 5%. In another embodiment, the new 6262A extruded product may realize the above strength values in combination with an elongation of at least 6% (L). In yet another embodiment, the new 6262A extruded product may realize the above strength values in combination with an elongation of at least 7% (L). In another embodiment, the new 6262A extruded product may realize the above strength values in combination with an elongation of at least 8% (L).

In one approach, a new extruded 6262A aluminum alloy product realizes at least one of (a) 18 vol. % cube (ED) texture and (b) a maximum ODF [001] intensity of at least 3.9, as measured per the EBSD Sample Procedure, below. In one embodiment, a new extruded 6262A aluminum alloy product realizes at least 19 vol. % cube (ED) texture, or at least 20 vol. % cube (ED) texture, or at least 21 vol. % cube (ED) texture, at least 22 vol. % cube (ED) texture, or at least 23 vol. % cube (ED) texture, at least 24 vol. % cube (ED) texture, or at least 25 vol. % cube (ED) texture, at least 26 vol. % cube (ED) texture, or at least 27 vol. % cube (ED) texture. In one embodiment, a new extruded 6262A aluminum alloy product realizes a maximum ODF [001] intensity of at least 3.8, or at least 4.0, or at least 4.2, or at least 4.4, or at least 4.6, or at least 4.8, or at least 5.0, or at least 5.2, or at least 5.4, or at least 5.6, or at least 5.8, or at least 6.0, or at least 6.2, or at least 6.4, or at least 6.6, or at least 6.8, or at least 7.0.

In one embodiment, the new 6xxx aluminum alloy is a new 6061 extruded product i.e., made by the inventive methods and/or systems described herein. The new 6061 extruded product may realize at least 5% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6061 product. In one embodiment, a new 6061 extruded product may realize at least 10% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6061 product of the same product form, size and temper. In another embodiment, a new 6061 extruded product may realize at least 15% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6061 product of the same product form, size and temper. In yet another embodiment, a new 6061 extruded product may realize at least 20% higher tensile yield strength (typical) and/or ultimate tensile strength (typical) than a conventionally press-quenched 6061 product of the same product form, size and temper. In one embodiment, a new extruded 6061 product realizes a tensile yield strength (typical) (L) of at least 22 ksi, or at least 24 ksi, or at least 26 ksi, or at least 28 ksi, or at least 30 ksi, or at least 32 ksi, or at least 34 ksi, or at least 36 ksi, or at least 38 ksi, or at least 40 ksi, or at least 42 ksi, or at least 44 ksi, or at least 46 ksi, or at least 47 ksi, or at least 48 ksi, or at least 49 ksi, or at least 50 ksi, or at least 51 ksi, or at least 52 ksi. In one embodiment, the new 6061 extruded product may realize the above strength values in combination with an elongation (longitudinal or L) of at least 8%. In another embodiment, the new 6061 extruded product may realize the above strength values in combination with an elongation of at least 10% (L). In yet another embodiment, the new 6061 extruded product may realize the above strength values in combination with an elongation of at least 12% (L). In another embodiment, the new 6061 extruded product may realize the above strength values in combination with an elongation of at least 14% (L).

In one approach, a new extruded 6061 aluminum alloy product realizes at least one of (a) 5 vol. % cube (ED) texture and (b) a maximum ODF [001] intensity of at least 2.0, as measured per the EBSD Sample Procedure, below. In one embodiment, a new extruded 6061 aluminum alloy product realizes at least 6 vol. % cube (ED) texture, or at least 7 vol. % cube (ED) texture, or at least 8 vol. % cube (ED) texture, at least 9 vol. % cube (ED) texture, or at least 10 vol. % cube (ED) texture, at least 11 vol. % cube (ED) texture, or at least 12 vol. % cube (ED) texture, at least 13 vol. % cube (ED) texture, or at least 14 vol. % cube (ED) texture, or at least 15 vol. % cube (ED) texture, at least 16 vol. % cube (ED) texture, or at least 17 vol. % cube (ED) texture. In one embodiment, a new extruded 6061 aluminum alloy product realizes a maximum ODF [001] intensity of at least 2.5, or at least 3.0, or at least 3.5, or at least 4.0, or at least 4.5, or at least 5.0, or at least 5.5, or at least 6.0, or at least 6.5, or at least 7.0, or at least 7.5, or at least 8.0, or at least 8.5, or at least 9.0, or at least 9.5, or at least 10.0, or at least 10.2, or at least 10.4, or at least 10.6, or at least 10.8.

V. Product Applications

The new 6xxx extruded aluminum alloy products described herein may be used in a variety of product applications, such as rods, bars and profiles. Such products may be used make transmission valves (e.g., for free-machining 6xxx aluminum alloys having Sn, Bi, and/or Pb). Automotive structural components may also be produced. The extrusions may also be used as electrical connectors and in general industrial applications.

VI. Definitions

“Hot working” such as by hot extruding means working the aluminum alloy product at elevated temperature, and generally at least 250° F. Strain-hardening is restricted/avoided during hot working, which generally differentiates hot working from cold working.

“Cold working” such as by cold drawing means working the aluminum alloy product at temperatures that are not considered hot working temperatures, generally below about 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.

VII. Miscellaneous

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.

The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

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.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating one embodiment of a method (100) for producing extruded 6xxx aluminum alloy products.

FIG. 2 is a block diagram illustrating one embodiment of system (200) for producing extruded 6xxx aluminum alloy products relative to the methods of FIG. 1.

FIG. 3a is a flowchart illustrating one method for producing extruded 6xxx aluminum alloy products in the T6 or T9 temper.

FIG. 3b is a flowchart illustrating one method for producing extruded 6xxx aluminum alloy products in the T8 temper.

FIG. 4 is a top-down schematic view of one embodiment of portions of a system for producing extruded 6xxx aluminum alloy products relative to the methods of FIG. 1.

FIG. 5a illustrates micrographs of a conventionally press-quenched 6026LF product.

FIG. 5b illustrates micrographs of a new 6026LF product made by the inventive systems and methods described herein.

FIG. 6a is a micrograph of a 6026LF product made with a conventional process employing a separate post-extrusion solution heat treatment.

FIG. 6b is a micrograph of a new 6026LF product made by the inventive systems and methods described herein.

FIGS. 7a-7b are graphs showing properties of a 6026LF product made by the inventive systems and methods described herein.

FIG. 8a illustrates micrographs of a new 6020 product made by the inventive systems and methods described herein.

FIG. 9a is a micrograph of a new 6020 product (50 micrometer scale) made by the inventive systems and methods described herein.

FIG. 9b is a micrograph of a 6020 product (50 micrometer scale) made with a conventional press-quench process.

FIGS. 9c-9d illustrate additional micrographs (200 micrometer scale) of a new 6020 product made by the inventive systems and methods described herein.

FIGS. 10a-10b are graphs showing properties of a 6020 product made by the inventive systems and methods described herein.

FIGS. 11a-11b illustrate micrographs of a new 6262A product made by the inventive systems and methods described herein.

FIGS. 12a-12b are graphs showing properties of a 6262A product made by the inventive systems and methods described herein.

FIG. 13a is a photograph showing machining chips of a 6262A product made with a conventional process employing a separate post-extrusion solution heat treatment.

FIG. 13b is a photograph showing machining chips of a 6262A product made by the inventive systems and methods described herein.

FIGS. 14a-14b are graphs showing properties of a 6061 product made by the inventive systems and methods described herein.

DETAILED DESCRIPTION

Example 1

A conventional 6026LF (lead free) aluminum alloy was produced by two different methods. The basic steps of the two methods are shown in Table 1, below.

TABLE 1
Method 1                     Method 2
(Conventional)               (Inventive)
Cast Billet                  Cast Billet
Homogenize Billet            Homogenize Billet
Cool to Ambient              Cool to Ambient
Preheat to 775-800° F.       Preheat above the solvus temperature
Hold at preheat temperature  Hold at preheat temperature
for 3 to 5 minutes           for ≈50 minutes
Reduce the temperature and   Move to extrusion press within
move to extrusion press      90 seconds (e.g., to achieve
(high heat losses)           a heat loss of ≤10° F.)
Extrude billet into rod      Extrude billet into rod
Discharge rod to ambient air Discharge rod to exit shroud
                             (e.g., to maintain the rod
                             above its solvus temperature)
Move rod from ambient        Move rod from heating shroud to
air to water bath            water sprays and then water bath
Temper to T6, T8 or T9       Temper to T6, T8 or T9

The systems used to conduct the second, inventive method are consistent with those illustrated in FIGS. 2 and 4.

Micrographs of the extrudates were taken in the longitudinal direction. FIG. 5a illustrates the microstructure of the 6026LF-T9 alloys processed via Method 1, i.e., a conventional press-quench. FIG. 5b illustrates the microstructure of the 6026LF-T9 alloys processed via Method 2, i.e., the inventive method. As shown, Method 1 results in the 6026LF product having large recrystallized grains near the surface. Conversely, Method 2 produces fine fibrous unrecrystallized grains, uniform in the cross-section direction. Moreover, as shown in FIG. 6b, the microstructure of Method 2 results in a uniform distribution of fine and small constituent particles, consistent with that of a conventionally processed rod that has a completely separate furnace solution heat treatment after extrusion (FIG. 6a).

FIG. 7a illustrates the strength properties achieved by 0.5625 inch extruded 6026LF-T9 rod extruded produced according to Method 2. FIG. 7b illustrates the elongation properties achieved by these same rods. As shown, the strength and elongation of the extruded rod significantly exceed the ASTM requirements for the 6026LF alloy. The measured property values are also shown in Table 2. (All values are relative to the longitudinal direction.)

TABLE 2
Mechanical Properties of 6026LF Alloy
		UTS	TYS	Elong.
	Item	(ksi)	(ksi)	(%)
	Billet 1-11	56.6	55.8	10
	Billet 2-10	57.0	56.5	9
	Billet 3-10	56.8	56.2	9
	Billet 6-10	56.9	56.1	8
	Billet 10-10	57.3	56.5	8
	Billet 13-10	56.2	55.9	9
	Billet 14-10	57.1	56.9	8

The new methods and systems described herein also produce improved microstructures and properties in other 6xxx aluminum alloys. For instance, FIG. 8a shows the microstructure of a 6020 alloy that has been prepared using the methods consistent with those illustrated in FIGS. 1 and 3b (T8 temper) and using systems consistent with those illustrated in FIGS. 2 and 4. As shown, the grains of the extruded 6020 alloy are fibrous and uniform in the cross section direction.

FIG. 9a illustrates a micrograph of a 6020 alloy product made by the inventive methods and systems described herein. FIG. 9b is a micrograph of a 6020 alloy product made by a conventional press-quench process. The new 6020 product has fewer large tin-bearing constituent particles and the tin-bearing constituent particles are spheroidized. Finer and better distributed tin-bearing phases contribute to improved machinability for the 6xxx free machining alloys. As also shown in FIGS. 9c-9d, the new 6020 product realizes small constituent particles are that are uniformly distributed. Such particle sizes and particle size distribution is consistent with that of a conventionally processed rod that has a completely separate furnace solution heat treatment after extrusion. The mechanical properties of the 6020 alloy in rod form (1.16 inch under 20%, 25% and 30% draw) produced by the inventive methods and systems in the T8 temper are shown in FIGS. 10a-10b. As shown, the strength and elongation values significantly exceed the 6020-T8 ASTM minimums. The measured property values are also shown in Table 3, below. (All values are relative to the longitudinal direction.)

TABLE 3
Mechanical Properties of 6020 Alloy
		UTS	TYS	Elong.
	Item	(ksi)	(ksi)	(%)
	R + 10f_20%_B1	45.3	42.9	15
	R + 10f_20%_B2	45.5	42.5	15
	R + 10f_25%_B1	46.7	43.3	15
	R + 10f_25%_B2	46.5	43.8	15
	R + 10f_30%_B1	47.3	45.2	15
	R + 10f_30%_B2	47.4	44.7	15
	R + 22f_20%_B1	45.9	43.2	15
	R + 22f_20%_B2	45.0	42.0	15
	R + 22f_25%_B1	46.7	43.8	15
	R + 22f_25%_B2	45.6	42.6	15
	R + 22f_30%_B1	47.6	45.2	15
	R + 22f_30%_B2	47.4	45.0	15

Alloy 6262A was also made by the inventive methods and systems (e.g., consistent with FIGS. 1 and 3a (T9 temper) and FIGS. 2 and 4). Again, as shown in FIGS. 11a-11b, the new 6262A products contain small constituent particles and the particle size distribution is uniform, which is consistent with that of a conventionally processed rod that has a completely separate furnace solution heat treatment after extrusion. The mechanical properties of the 6262A alloy in rod form (0.5626 inch rod) produced by the inventive methods and systems in the T9 temper are shown in FIGS. 12a-12b. As shown, the strength and elongation values significantly exceed the 6262A-T9 ASTM minimums. The measured property values are also shown in Table 4, below. (All values are relative to the longitudinal direction.)

TABLE 4
Mechanical Properties of 6262A Alloy
		UTS	TYS	Elong.
	Item	(ksi)	(ksi)	(%)
	2-2-PQ	54.1	53.1	7
	2-13-PQ	54.4	53.3	7
	2-7-PQ	54.1	53.1	8
	3-1-PQ	54.6	53.6	8
	3-6-PQ	54.7	53.7	8
	3-7-PQ	54.9	53.8	7
	3-14-PQ	54.9	53.8	6
	4-7-PQ	54.8	53.7	7
	4-10-PQ	54.6	53.6	7
	4-12-PQ	55.0	53.8	8
	7-1-PQ	55.2	54.1	7
	8-7-PQ	55.3	54.2	6
	8-12-PQ	54.9	53.8	7
	9-1-PQ	54.4	53.3	7
	9-6-PQ	54.9	53.8	7
	9-13-PQ	54.1	53.0	7
	a-PQ	55.0	53.8	6
	b-PQ	55.4	54.3	6

The machinability of the 6262A rods produced by the inventive methods and systems is also significantly improved. As shown in FIG. 13a, 6262A-T9 products made using a conventional post-extrusion solution heat treatment typically exhibit a large amount of extra-long chips. Conversely, as shown in FIG. 13b, the new 6262A-T9 products manufactured using the inventive methods and systems described herein exhibit finer chips, which shows superior machinability.

Alloy 6061 was also made by the inventive methods and systems (e.g., consistent with FIGS. 1-2a (T6 temper) and FIGS. 3-4). The mechanical properties of the 6061 alloy in rod form (1.50 inch rod) produced by the inventive methods and systems in the T6 temper are shown in FIGS. 14a-14b. As shown, the strength and elongation values again significantly exceed the 6061-T6 ASTM minimums. The measured property values are also shown in Table 5, below. (All values are relative to the longitudinal direction.)

TABLE 5
Mechanical Properties of 6061 Alloy
		UTS	TYS	Elong.
	Item	(ksi)	(ksi)	(%)
	6061-1 TR	53.1	50.1	16
	6061-2 TR	54.0	51.2	16
	6061-3 TR	52.1	48.9	16
	6061-1 TF	55.1	51.9	16
	6061-2 TF	55.6	52.4	16
	6061-3 TF	55.4	52.2	16

Example 2

Microstructure data for the alloys was obtained per the EBSD sample procedure shown below. Table 6 provides some illustrative properties of the alloys. The reported maximum ODF texture intensities are in the [001] plane, through the cross section. The cube texture and grain size values are in the transverse direction.

TABLE 6
Microstructure Data
	Max. ODF	Cube Texture	Grain Size
Alloy	Intensity	(ED)(Vol. %)	(micrometers)
6020-T8	3.545	15%	52
(Conventional SHT)
6020-T8	3.439	16%	74
(Conventional PQ)
6020-T8	6.982	27%	142
(Inventive Method)
6262A-T9	5.473	22%	192
(Conventional SHT)
6262A-T9	3.864	17%	64
(Conventional PQ)
6262A-T9	6.282	24%	184
(Inventive Method)
6026LF-T9	2.751	4%	1310
(Conventional SHT)
6026LF-T9	9.621	16%	33
(Conventional PQ)
6026LF-T9	11.225	19%	23
(Inventive Method)
6061-T6	1.558	6%	171
(Conventional SHT)
6061-T6	1.995	4%	137
(Conventional PQ)
6061-T6	10.824	17%	51
(Inventive Method)

As shown in Table 6, the alloys produced by the invention process realize a much higher maximum texture intensity over the conventional press quenched alloys and even the solution heat treated alloys. For instance, the new 6020 extruded alloy has a maximum ODF texture intensity that is 203% higher than the maximum ODF texture intensity of the conventionally extruded and press-quenched 6020 alloy (6.982/3.439=2.03).

As also shown in Table 6, the alloys produced by the invention process realize more cube ED (extrusion direction) texture as compared to the conventional press quenched alloys and even the solution heat treated alloys. For instance, the new 6020 extruded alloy includes 9 vol. % more cube ED texture than the conventionally extruded and press-quenched 6020 alloy (26 vol. % versus 17 vol. %).

Textured aluminum alloys have grains whose axes are not randomly distributed. Since the images can vary based on various factors, measured texture intensities are generally normalized by calculating the amount of background intensity, or random intensity, and comparing that background intensity to the intensity of the textures of the image. Thus, the relative intensities of the obtained texture measurements are dimensionless quantities that can be compared to one another to determine the relative amount of the different textures within a polycrystalline material. For example, an OIM analysis may determine a background (random) intensity and use orientation distribution functions (ODFs) to produce ODF intensity values. These ODF intensity values may be representative of the amount of texture within a given aluminum alloy (or other polycrystalline material).

For the present application, ODF intensities are measured according to the EBSD sample procedure (described below), or a substantially similar OIM procedure (x-ray diffraction is not used), where a series of ODF plots containing intensity (times random) representations may be created. The new 6xxx aluminum alloy products generally have a high maximum ODF intensity, indicating a high amount of texture. It is believed that the high amount of texture in the new 6xxx aluminum alloy products may contribute to their improved properties.

In one embodiment, the new extruded 6xxx aluminum alloy product realizes a maximum ODF intensity that is at least about 10% higher than a conventionally extruded and press-quenched 6xxx aluminum alloy product of comparable product form, composition and temper. For instance, if a conventionally extruded and press-quenched 6026 alloy realized a maximum ODF intensity of 4.0, then a new 6026 aluminum alloy product made by the new processing disclosed herein may realize a maximum ODF intensity of at least 4.4 (10% higher than the 4.0). In other embodiments, the new extruded 6xxx aluminum alloy product may realize a maximum ODF intensity that is at least about 20% higher, or at least about 40% higher, or at least about 40% higher, or at least about 60% higher, or at least about 80% higher, or at least about 100% higher, or at least about 120% higher, or at least about 140% higher, or at least about 160% higher, or at least about 180% higher, or at least about 200% higher, or at least about 220% higher, or at least about 240% higher, or at least about 260% higher, or at least about 300% higher, or at least about 340% higher, or at least about 360% higher, or at least about 380% higher, or at least about 400%, or at least about 420% higher, or at least about 440% higher, or at least about 460% higher, or at least about 480% higher, or at least about 500% higher, or more, than a conventionally extruded and press-quenched 6xxx aluminum alloy product of comparable product form, composition and temper.

In one embodiment, the new extruded 6xxx aluminum alloy product realizes at least 1 vol. % more cube ED texture that than a conventionally extruded and press-quenched 6xxx aluminum alloy product of comparable product form, composition and temper. For instance, if a conventionally extruded and press-quenched 6026 alloy realized 15 vol. % cube ED texture, then a new 6026 aluminum alloy product made by the new processing disclosed herein may realize 16 vol. % cube ED texture (1 vol. % more than 15 vol. %). In other embodiments, the new extruded 6xxx aluminum alloy product may realize at least 2 vol. % more, or at least 3 vol. % more, or at least 4 vol. % more, or at least 5 vol. % more, or at least 6 vol. % more, or at least 7 vol. % more, or at least 8 vol. % more, or at least 9 vol. % more, or at least 10 vol. % more, or at least 11 vol. % more, or at least 12 vol. % more, or at least 13 vol. % more than a conventionally extruded and press-quenched 6xxx aluminum alloy product of comparable product form, composition and temper.

EBSD Sample Procedure

• • Electron backscatter diffraction (EBSD) is carried out using a Thermo-Scientific Apreo S scanning electron microscope (SEM), or similar. The SEM operating conditions are a spot size of 51 nA at an accelerating voltage 20 kV with the sample tilted at 68° and a working distance of 17 mm. The EBSD patterns are collected using an EDAX Velocity camera with 4×4 binning and EDAX Orientation Image Microscopy software (OIM v. 7.3.1), or similar. The EBSD scans are carried out using a square grid scanning pattern and dimensions of 2.8 mm tall and through thickness.
  • The collected scan data is processed using OIM TSL Analysis software (v. 8.0). The scan data is cleaned up using two processes. The first clean-up process is a neighbor orientation correlation with a minimum confidence of 0.1 and a grain tolerance angle of 5°. The second clean-up process is a grain dilation which specified a minimum grain size of five data points containing multiple rows. These two processes were carried out with one iteration of clean up.
  • A grain is defined as have a grain tolerance angle of 5° and a minimum number of 5 points. The grain shape is assumed to be spherical. Grain size charts are then calculated using the grain size diameters. In the charts, grain size diameters were binned and plotted against the area fraction.

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. Various ones of the unique aspects noted hereinabove may be combined to yield various new 6xxx aluminum alloy products having an improved combination of properties. Additionally, these and other aspects and 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.

Claims

1. A 6xxx extruded product comprising: wherein, when the 6xxx extruded product includes less than 0.07 wt. % Mn, the 6xxx extruded product comprises a recrystallized microstructure as measured from T/10 to 9T/10 of the 6xxx extruded product;

from 0.2 to 2.0 wt. % Si;

from 0.2 to 1.5 wt. % Mg;

one of either: (i) from 0.07 to 1.0 wt. % Mn; or (ii) less than 0.07 wt. % Mn;

up to 1.5 wt. % Bi;

up to 1.5 wt. % Sn;

up to 1.0 wt. % Cu;

up to 1.0 wt. % Zn;

up to 0.7 wt. % Pb;

up to 0.7 wt. % Fe;

up to 0.35 wt. % Cr;

up to 0.35 wt. % V;

up to 0.25 wt. % Zr;

up to 0.20 wt. % Ti;

the balance being aluminum, optional incidental elements and impurities;

wherein, when the 6xxx extruded product includes from 0.07 to 1.0 wt. % Mn, the 6xxx extruded product comprises an unrecrystallized microstructure as measured from T/10 to 9T/10 of the 6xxx extruded product;

wherein the unrecrystallized microstructure comprises at least 50 vol. % unrecrystallized grains;

wherein at least 60% of the unrecrystallized grains are fibrous grains;

wherein the fibrous grains have an aspect ratio (grain length/diameter) of at least 5:1;

wherein the average grain size of the unrecrystallized microstructure is not greater than 200 microns; or

wherein the recrystallized microstructure comprises at least 50 vol. % recrystallized grains;

wherein at least 60% of the recrystallized grains are equiaxed grains having as aspect ratio of not greater than 5:1 (L:LT);

wherein the average grain size of the recrystallized microstructure is not greater than 200 microns.

2. The 6xxx extruded product of claim 1, wherein the 6xxx extruded product comprises at least 1 vol. % more cube (ED) texture as compared to a conventional 6xxx extruded product;

wherein the conventional 6xxx extruded product is conventionally press-quenched and is of a comparable composition, product form, size and temper.

3. The 6xxx extruded product of claim 2, wherein the 6xxx extruded product comprises at least 2 vol. % more cube (ED) texture as compared to the conventional 6xxx extruded product.

4. The 6xxx extruded product of claim 2, wherein the 6xxx extruded product comprises a maximum ODF [001] texture intensity, wherein the maximum ODF [001] texture intensity is at least 10% higher than a maximum ODF [001] texture intensity of a conventional 6xxx extruded product;

wherein the conventional 6xxx extruded product is conventionally press-quenched and is of a comparable composition, product form, size and temper.

5. The 6xxx extruded product of claim 4, wherein the extruded 6xxx extruded product realizes a maximum ODF [001] texture intensity that is at least about 20% higher than the conventional 6xxx extruded product.

6. A method comprising:

(a) heating a billet of a 6xxx aluminum alloy to a preheat temperature;

(b) holding the billet at the preheat temperature for a time sufficient to dissolve at least some precipitate hardening phases of the billet;

(c) after the holding step, immediately transferring the billet to an extrusion apparatus;

(d) extruding the billet into an extruded product in the extrusion apparatus, wherein, during the extruding, both the billet and the extruded product are maintained at or above the preheat temperature;

(e) discharging the extruded product from the extrusion apparatus and into an exit shroud, wherein the exit shroud maintains the extruded product within 100° F. of a solvus temperature of the 6xxx aluminum alloy;

(f) moving the extruded product from the heating shroud to a quenching apparatus, wherein the quenching apparatus comprises at least one of a water spray and a water bath, and wherein the quenching apparatus quenches the extruded product to a temperature below 125° F. and at a cooling rate of at least 1° F./second.

7. A system comprising:

(a) a furnace adapted to preheat an extrusion billet of a 6xxx aluminum alloy;

(b) an extrusion apparatus adjacent to and downstream of the furnace, wherein the extrusion apparatus is adapted to extrude the billet into an extruded product;

(c) an exit shroud adjacent to and downstream of the extrusion apparatus, wherein the exit shroud is adapted to maintain the extruded product within 100° F. of a solvus temperature of the 6xxx aluminum alloy;

(d) a quenching apparatus located immediately adjacent to and downstream of the extrusion apparatus, wherein the quenching apparatus is adapted to cool the extruded product received from the exit shroud to a temperature below 125° F. and at a cooling rate of at least 1° F./second.