Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED 6XXX ALUMINUM ALLOYS
Background
[ow] 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. Patent 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
[002] 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
[003] 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.
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[004] 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.
[005] 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.
[006] 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.
[007] 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 (0) (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.
[008] 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
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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.
[009] 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.
[0010] 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
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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).
[0011] Non-limiting embodiments of a preheating step are shown in
FIGS. 3a-3b. As
shown, the billet is heated (a) from room temperature (Troom) to a preheat
temperature, which,
in this case is the metallurgical required temperature (TimR) or the
temperature required to
achieve high mechanical properties. As shown, the metallurgical required
temperature (TmR)
exceeds the solvus temperature (Tsoh-us). As also shown, the preheat holding
time, referred to
as tmr 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.
[0012] As further shown in FIGS. 3a-3b, the preheat temperature
(TmR) is below the
incipient melting temperature or Tsolidus, 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 Tsolidus 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.
[0013] 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
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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.
[0014] 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.
[0015] 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 (Tim), 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
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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.
[0016] 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.
[0017] 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
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)
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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.
[0018] 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.
[0019] 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.
[0020] 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...
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[0021] 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
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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.
[0022] 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.
[0023] 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 (Troom)). 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.
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[0024] 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.
[0025] 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.
[0026] 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
[0027] 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.
[0028] 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
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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.
[0029] 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.
[0030] 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.
[0031] 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
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include those associated with the theta (0), omega (S2) and/or S phases, among
others. In the
case of 7xxx aluminum alloys, applicable solvus temperatures include those
associated with
the eta (ii) phase, among others.
III. Microstructure
[0032] 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.
[0033] 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
[0034] As noted above, the new 6xxx aluminum alloys may realize an
improved
combination of properties, such as an improved combination of strength and
elongation.
[0035] 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
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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.
[0036] 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% (T,). Tn yet an other
embodiment, the new 60261,F
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).
[0037] 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.
[0038] 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-
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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).
[0039] 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 36, 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 7Ø
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[0040] 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).
[0041] 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
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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 7Ø
[0042] 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).
[0043] 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,
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or at least 15 vol. % cube (ED) texture, at least 16 vol. ()/0 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
[0044] 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
[0045] "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.
[0046] "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).
[0047] Temper definitions are per ANSI H35.1 (2009), entitled
"American National
Standard Alloy and Temper Designation Systems for Aluminum," published by The
Aluminum
Association.
[0048] Strength and elongation are measured in accordance with
ASTM E8/E8M-16a and
B557-15.
VII. Miscellaneous
[0049] 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.
[0050] 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
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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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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
[0055] FIG. 1 is a block diagram illustrating one embodiment of a
method (100) for
producing extruded 6xxx aluminum alloy products.
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[0056] 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.
[0057] FIG. 3a is a flowchart illustrating one method for
producing extruded 6xxx
aluminum alloy products in the T6 or T9 temper.
[0058] FIG. 3b is a flowchart illustrating one method for
producing extruded 6xxx
aluminum alloy products in the T8 temper.
[0059] 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.
[0060] FIG. 5a illustrates micrographs of a conventionally press-
quenched 6026LF
product.
[0061] FIG. 5b illustrates micrographs of a new 6026LF product
made by the inventive
systems and methods described herein.
[0062] FIG. 6a is a micrograph of a 6026LF product made with a
conventional process
employing a separate post-extrusion solution heat treatment.
[0063] FIG. 6b is a micrograph of a new 6026LF product made by the
inventive systems
and methods described herein.
[0064] FIGS. 7a-7b are graphs showing properties of a 6026LF
product made by the
inventive systems and methods described herein.
[0065] FIG. 8a illustrates micrographs of a new 6020 product made
by the inventive
systems and methods described herein.
[0066] FIG. 9a is a micrograph of a new 6020 product (50
micrometer scale) made by the
inventive systems and methods described herein.
[0067] FIG. 9b is a micrograph of a 6020 product (50 micrometer
scale) made with a
conventional press-quench process.
[0068] FIGS. 9c-9d illustrate additional micrographs (200
micrometer scale) of a new 6020
product made by the inventive systems and methods described herein.
[0069] FIGS. 10a-10b are graphs showing properties of a 6020
product made by the
inventive systems and methods described herein.
[0070] FIGS. ha-1 lb illustrate micrographs of a new 6262A product
made by the
inventive systems and methods described herein.
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[0071] FIGS. 12a-12b are graphs showing properties of a 6262A
product made by the
inventive systems and methods described herein.
[0072] 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.
[0073] FIG. 13b is a photograph showing machining chips of a 6262A
product made by
the inventive systems and methods described herein.
[0074] FIGS. 14a-14b are graphs showing properties of a 6061
product made by the
inventive systems and methods described herein.
Detailed Description
[0075] Example 1
[0076] 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 for 3 to 5 Hold at preheat temperature for 50
minutes minutes
Move to extrusion press within 90
Reduce the temperature and move to
seconds
extrusion press
(e.g., to achieve a heat loss of <
(high heat losses)
F)
Extrude billet into rod Extrude billet into rod
Discharge rod to exit shroud
Discharge rod to ambient air (e.g., to maintain the rod
above its
solvus temperature)
Move rod from ambient air to water Move rod from heating
shroud to
bath water sprays and then water
bath
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Method 1 Method 2
(Conventional) (Inventive)
Temper to 16, 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.
[0077] 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).
[0078] 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 El ong.
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
[0079] 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
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illustrated in FIGS. 2 and 4. As shown, the grains of the extruded 6020 alloy
are fibrous and
uniform in the cross section direction.
[0080] 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 sph eroi
di zed. 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
Item (ksi) (ksi) Elong. (%)
R+10f 20% B 1 45.3 42.9 15
R+10f 20% B2 45.5 42.5 15
R+10f 25% Bl 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% B I 46.7 43.8 15
R+22f 25% B2 45.6 42.6 15
R+22f 30% B 1 47.6 45.2 15
R+22f 30% B2 47.4 45.0 15
[0081] 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.
lla-1 lb, 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
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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
Item (ksi) (ksi) Elong. (%)
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
[0082] 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.
[0083] 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
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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
[0084] Example 2
[0085] 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)
6020-18
(Conventional SHT) 3.545 15% 52
6020-18
(Conventional PQ) 3.439 16% 74
6020-T8
(Inventive Method) 6.982 27% 142
6262A-T9
(Conventional SHT) 5.473 22% 192
6262A-T9
(Conventional PQ) 3.864 17% 64
6262A-T9
(Inventive Method) 6.282 24% 184
6026LF-T9
(Conventional SHT) 2.751 4% 1310
6026LF-T9
(Conventional PQ) 9.621 16% 33
6026LF-T9
(Inventive Method) 11.225 19% 23
6061-T6
(Conventional SHT) 1.558 6% 171
6061-T6
(Conventional PQ) 1.995 4% 137
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Max. ODF Cube Texture Grain Size
Alloy Intensity (ED)(Vol. %)
(micrometers)
6061-T6
(Inventive Method) 10.824 17% 51
[0086] 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).
[0087] 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. %).
[0088] 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 OM 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).
[0089] For the present application, ODF intensities are measured
according to the EBSD
sample procedure (described below), or a substantially similar OTIV1 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.
[0090] 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
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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.
[0091] 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.
[0092] 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 4x4 binning and EDAX Orientation Image Microscopy
softeware
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(0IM v. 7.3.1), or similar. The EB SD 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 OTM 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.
[0093] 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.
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