[0001] This invention concerns a method of producing improved aluminum alloy elongate products
and components by operations including extrusion; and specifically improved elongated
products and components that are particularly useful in the manufacture of vehicle
primary structures.
[0002] It is known to manufacture a vehicle frame by providing separate subassemblies, each
subassembly being composed of several separate components that can include lineal
frame members. Each subassembly is manufactured by joining together several members
by means of a node structure that can be a cast, extruded, or sheet component. The
frames and subassemblies can be assembled by adhesive bonding, welding, or mechanical
fastening; or by combinations of these and other joining techniques. An example of
such a vehicle frame structure is available in United States Patent No. 4,618,163,
entitled "Automotive Chassis" the entire contents of which are incorporated herein
by reference. Aluminum alloys are highly desirable for such vehicle frame constructions
because they offer low density, good strength and corrosion resistance. Moreover,
aluminum alloys can be employed to improve the vehicle frame stiffness and performance
characteristics. Use of aluminum provides the potential for environmental benefits
and efficiencies through a lightweight aluminum vehicle frame that also demonstrates
reduced fuel consumption due to the lightweighting. Finally, the application of aluminum
alloy components in a vehicle frame presents an opportunity to ultimately recycle
the aluminum components/subassemblies when the useful life of the vehicle is spent.
Moreover, it is believed that an aluminum vehicle frame retains the perceived strength
and crashworthiness typically associated with much heavier, conventional steel frame
vehicle designs.
[0003] As suggested above important considerations for aluminum primary automotive body
structures include crashworthiness in conjunction with reducing the overall vehicle
weight and/or improving vehicle performance. For the automotive application, crashworthiness
reflects the ability of a vehicle to sustain some amount of collision impact without
incurring unacceptable distortion of the passenger compartment or undue deceleration
of the occupants. Upon impact, the structure should deform in a prescribed manner;
the energy of deformation absorbed by the structure should balance the kinetic energy
of impact; the integrity of the passenger compartment should be maintained; and the
primary structure should crush in such a manner as to minimize the occupant deceleration.
Various standard tests can be used to evaluate the physical and mechanical properties
of an aluminum alloy for use in an automotive structure or other applications. As
examples, tensile testing and standard formability tests can be used to provide information
on strength and relative performance expectations, or a tear test can be used to examine
fracture characteristics and provide a measure of the resistance to crack growth or
toughness under either elastic or plastic stresses. These and other test methods are
used to examine the general performance of materials representative of those used
for the manufacture of vehicle components, subassemblies, and frames. However, few
standard tests are available to allow the evaluation of aluminum alloy components
intended for use in primary body structures. Accordingly, in addition to the tests
described above, it is believed that a static axial crush test allows the evaluation
of the response of a vehicle frame component to axial compressive loading. If used
for evaluation of component geometries designed to provide absorb energy under compressive
loading, the static axial crush test provides the severe conditions necessary to examine
a component's response to compressive loading. During the static axial crush test,
a specified length of an energy absorbing component is compressively loaded at a predetermined
rate creating a final deformed component height of approximately half the original
free length or less. Various modes of collapse can be experienced under these conditions;
including: regular folding - stable collapse, irregular folding, and bending. The
desired response for evaluation of energy absorbing components is stable axial collapse
characterized by regular folding. The crushed sample is examined to determine material
response to the severe deformation created during this test. It is generally desirable
to demonstrate the ability to deform without cracking. In this case, samples are visually
examined following static axial crush testing and assigned a rating based on the appearance
of the deformed samples. The results of the examination are registered on a scale
of from 1 to 3. A "3" indicates that the area proximate the fold shows evidence of
open cracking that is often visible to the naked eye and roughening damage. A "3"
rated material is considered to be unacceptable. A "2" indicates that the area proximate
the folds or displaced side wall material of the extrusion is roughened and may be
slightly cracked, but the basic integrity of the side wall is maintained. A sample
rated "2" is better than one rated a "3" but not as good as a sample rated "1". A
rating of "1" indicates that the crushed extrusion contains no cracking or roughened
areas and the folds are substantially smooth; this is the preferred material response
following the static axial crush test.
[0004] The ability of a structure or structural component to absorb energy and deform in
a desired, progressive manner under compressive loading during both static and dynamic
crash testing is a function of both the component design, e.g., geometry, cross-section
shape, size, length, thickness, joint types included in the assembly, and the properties
of the material from which the component is manufactured, i.e., yield and ultimate
tensile strength at the actual loading rate, modulus of elasticity, fracture behavior,
etc. Various aluminum alloys are potential candidates for the manufacture of a primary
body structure which includes such energy absorbing components. For example, 6XXX
alloys, could be utilized in the production of extruded components for incorporation
into aluminum intensive vehicles. The 6XXX series alloys are a popular family of aluminum
alloys, designated as such in accordance with the Aluminum Association system wherein
the 6XXX series refers to heat treatable aluminum alloys containing magnesium and
silicon as their major alloying additions. Strengthening in the 6XXX alloys is accomplished
through precipitation of Mg2Si or its precursors. The 6XXX are widely used in either
the naturally aged -T4 or artificially aged -T6 tempers. This series of alloys also
commonly includes other elements such as chromium, manganese, or copper, or combinations
of these and other elements for purposes of forming additional phases or modifying
the strengthening phase to provide improved property combinations.
[0005] The 6XXX alloys are commonly used for production of architectural shapes, and because
these products are most often used in applications requiring only a minimum strength
level the 6XXX alloys typically are air quenched in production due to cost considerations.
Alloy 6063 represents one of the most widely used 6XXX products. It provides typical
yield strengths of 90 MPa [13 ksi], 145 MPa [21 ksi], and 215 MPa [31 ksi] in the
naturally aged -T4 and artificially aged -T5 and -T6 tempers, respectively. By accepted
industry convention, both the -T5 and -T6 temper designations for extrusions can refer
to a product which has been press benched and artificially aged in lieu of the strict
definition of -T6 that includes a solution heat treatment and quenching operation.
[0006] Quenching from elevated temperature processing operations is often critical to the
development of properties and performance required of the final product. The objective
of quenching is to retain the Mg, Si and other elements in the solid solution resulting
from an elevated temperature operation such as extrusion. In the case of extrusion,
the product is often quenched as it exits the extrusion press to avoid the additional
cost associated with a separate solution heat treatment and quenching operation. Water
quenching can be used to provide a fast cooling rate from the extrusion temperature.
A fast cooling rate provides the best retention of the elements in solid solution.
However water quenching creates the need for additional equipment and can create excessive
distortion and the need for subsequent processing to correct the shape prior to use.
Air cooling is commonly used for press quenching of 6063 products. Air cooling reduces
the distortion experienced and improves dimensional capability in hollow products.
However, 6XXX products typically exhibit some quench sensitivity or loss of strength
or other properties with reduced quench rates experienced in air quenching. Quench
sensitivity is due to precipitation of elements from the solid solution during a slow
quench. This precipitation typically occurs on grain boundaries and other heterogeneous
sites in the microstructure. Precipitation during the quenching operation makes the
solute unavailable for precipitation of strengthening phases during subsequent aging
operations. A slow quench typically results in a loss of strength, toughness, formability
or corrosion resistance. A slow quench can also adversely effect the fracture performance
of the product by promoting low energy grain boundary fracture. Quench sensitivity
with respect to yield strength is generally small in dilute alloys such as 6063. However,
pronounced quench sensitivity can be observed with respect to toughness and toughness
indicators as well as other properties which are strongly influenced by the fracture
behavior of the material. Differences are often noted in the results obtained through
tear tests, and formability evaluations. Dramatic influences of the quench rate have
also been noted in the results obtained using the static axial crush test in common
commercial extrusion materials such as 6063. In order to overcome the loss of desired
properties, a separate solution heat treatment and quench, or an in line press spray
water quench can be used to provide cooling at the required rate to minimize precipitation
during quenching. However, as indicated above, water quenching can create distortion,
inhibit process speed, require additional processing for dimensional correction, and
limit the ability to produce component profiles to tolerance. The strictest of tolerances
must be maintained during the assembly of a vehicle subassembly or frame. Quench distortion
associated with use of a water quenching operation adversely effects the production
of a complex, thin walled, hollow extrusion, potentially distorting it and rendering
it out of tolerance for the desired application and in need of further labor intensive
correction.
[0007] U.S. Patent No. 4,525,326 teaches that the quench sensitivity with respect to strength
of a 6XXX alloy (Si, Fe, Cu, Mg) can be improved by the addition of vanadium. Specifically,
the patent discloses the addition of 0.05 to 0.2% vanadium and manganese in a concentration
equal to 1/4 to 2/3 of the iron concentration to an aluminum alloy for the manufacture
of extruded products. Notwithstanding such efforts to develop alloys that offer reduced
quench sensitivity with respect to strength; there remains a need for alloys that
provide reduced quench sensitivity with respect to static axial crush performance.
[0008] An alloy that could be air quenched would provide the ability to produce thin walled
hollow extruded shapes meeting the dimensional capabilities desired for assembly of
automotive structures and providing the characteristics desired for use in the final
structure including good strength and the ability to deform in a regular way in components
designed to absorb energy when compressively loaded in the event of a collision; and
allow production of these components in a cost effective manner.
[0009] Therefore, it is of interest:
to provide an aluminum alloy component characterized by excellent static axial crush
performance;
to provide an aluminum alloy characterized by reduced quench sensitivity with respect
to static axial crush performance and other characteristics required for application
in automotive structures;
to provide an aluminum alloy capable of an increased range of shapes including thin
walled hollow extrusions and improved dimensional capability for use in the manufacture
of aluminum intensive vehicles or similar structures;
to provide an improved aluminum alloy; and
to provide a method of manufacturing an improved elongated aluminum alloy product.
[0010] In accordance with the present invention there is provided the method of producing
an improved elongate aluminum alloy product comprising:
providing an alloy comprising essentially 0.45 to 0.7% magnesium, 0.35 to 0.6% silicon,
0.1 to 0.35% vanadium and 0.1 - 0.4% iron, the balance substantially aluminum and
incidental elements and impurities;
extruding a body of said alloy; and
quenching said body of said alloy.
[0011] Unless indicated otherwise, all composition percentages set forth herein are by weight.
Additionally, this aluminum alloy demonstrates relatively lower quench sensitive with
respect to the static axial crush performance and provides good strength, formability
and corrosion resistance. The alloy composition of this invention is therefore ideally
suited for air quench yet capable of an increased range of shapes and improved dimensional
capability. The quenching process can include the application of a forced air quenching
of the extruded product in addition to the steps of homogenization, reheating, extrusion,
natural and/or artificial aging.
[0012] The above as well as other features and advantages of the present invention can be
more clearly appreciated through consideration of the detailed description of the
invention in conjunction with the sole figure which is a graph demonstrating the characteristics
of a forced air cooled product according to this invention.
[0013] In accordance with this invention, the alloy composition is formulated to contain
about 0.45 to 0.7% magnesium, preferably about 0.48 to 0.64% magnesium, and about
0.35 to 0.6%, preferably about 0.4 to 0.51% silicon, and about 0.1 to 0.35%, preferably
about 0.2% vanadium, and, 0.1 - 0.4% iron, preferably 0.15 to 0.3%, the balance substantially
aluminum and incidental elements and impurities. The alloy composition of this invention
is free from the intentional addition of copper and is consistent with the Aluminum
Association composition standards for acceptable levels of impurities. The alloy is
typically solidified into extrusion ingot by continuous casting or semi-continuous
casting into a shape suitable for extrusion which is typically a cylindrical ingot
billet. The ingot can be machined or scalped to remove surface imperfections, if desired,
or it can be extruded without machining if the surface is suitable. The extrusion
process produces a substantially reduced diameter but greatly increased length compared
to the extrusion billet. Before extrusion, the metal is typically subjected to thermal
treatments to improve workability and properties. The as-cast billet can be homogenized
above the Mg2Si solvus temperature to allow dissolution of existing Mg2Si particles
and reduce chemical segregation resulting from the casting process. Following homogenization,
ingot can be allowed to air cool. Prior to extrusion, billets are reheated to the
hot working temperature and extruded by direct or indirect extrusion practices. It
is an important preference in practicing the invention that extrusion be conducted
at cylinder temperatures just before extrusion which are typically 50 - 100°F. less
than that of the extrusion; typically within the range of about 700°F. up to about
1000°F., preferably at a temperature of 900°F.
[0014] Extrusion circle size varies but the extrusion typically has a wall thickness of
1.5 mm and greater. The extrusion typically has ends cropped off and can be cut to
desired lengths for subsequent operations. The extruded shape enters a quenching zone
where it is then quenched, preferably by application of forced air cooling practices,
that reduces the temperature of the extrusion to between approximately 250°F. to 450°F.
Preferably the extruded product is at a temperature of about 350°F. as it exits the
quenching zone. The cooling rate, that is the change in temperature of the extruded
product as it traverses the quench zone is ultimately a function of the geometry of
the extruded component, the speed at which the extruded product traverses the quenching
zone, and the air temperature. In experimental trials, product was provided with a
forced air quench to produce a cooling rate of 3 to 6°F./sec [2 to 3°C./sec]. The
extruded component can then be stretched about 1/4 to 1-1/2% to straighten it if desired.
The extruded product is naturally aged. Suitable properties are achieved within a
natural aging period between four and thirty days.
[0015] The extruded component, with or without subsequent stretching, can be artificially
aged to develop its strength properties. This typically includes heating above 250°
or 270°F., typically above 300°F., for instance from about 330° to about 450°F. for
a period of time from about an hour or a little less to about 10 or 15 hours, typically
about 2 or 3 hours for temperatures about 350° to 400°F. The time used varies inversely
with temperature (higher temperature for less time or lower temperature for longer
time) and this develops so called peak or -T6 strength.
EXAMPLES
[0016] Extrusions representing three combinations of aluminum alloy composition and thermal
processing were prepared for evaluation. Samples of each composition were extruded
using water quenching and air quenching. The alloys designated "A" and "B" are 6063
type compositions that do not contain copper. Samples "A" were homogenized and artificially
aged using the practices recommended by the Aluminum Association for production of
6063-T6; homogenization 4 hours at 1075°F. and aging 8 hours at 350°F. All other process
steps were identical to those used for production of the other example materials.
Samples "B" were homogenized and artificially aged according to the process of the
invention. Finally, the alloy of this invention is designated "C" and contains approximately
0.2 vanadium. Table I also provides the registered composition range for 6063 aluminum
alloy.
Table I
Composition |
Samples |
Alloy |
Si |
Fe |
Cu |
Mg |
V |
A |
6063 |
0.48 |
0.24 |
0.02 |
0.47 |
--- |
A |
6063 |
0.48 |
0.24 |
0.02 |
0.47 |
--- |
|
|
|
|
|
|
|
B |
6XXX |
0.51 |
0.2 |
--- |
0.48 |
--- |
B |
6XXX |
0.51 |
0.2 |
--- |
0.48 |
--- |
|
|
|
|
|
|
|
C |
New |
0.51 |
0.2 |
--- |
0.48 |
0.2 |
C |
New |
0.51 |
0.2 |
--- |
0.48 |
0.2 |
|
|
|
|
|
|
|
6063 |
AA range |
0.2-0.6 |
0.35 max |
0.10 max |
0.45-0.9 |
|
[0017] Table II sets forth the data obtained from the analysis of extruded product produced
using water quenching. Three alloys, the commercially available 6063 (sample "A"),
the 6063 type alloy (sample "B"), and the alloy of this invention (sample "C") were
used to produce extruded product using a conventional water quench process. The extruded
product was then aged to the -T6 temper and evaluated using the static axial crush
test and standard tensile tests. In the evaluation of the product representing these
materials, 3" sections of the extrusion were saw cut with ends parallel and subjected
to axial displacement. This test rendered a crushed sample approximately 1.25" in
height having one (1) severe fold. The deformed regions of the crushed product were
then subject to a visual examination and assigned a crush rating as per the rating
system described previously where a rating of "1" constitutes the desired outcome
and a rating of "3" indicates the presence of cracking. The second column of Table
II provides the results of a static axial crush test. As can be seen, all three alloys,
when subject to water quenching, showed the preferred performance in the static axial
crush test.
Table II
Spray Water Quenched Extruded Product |
Longitudinal Tensile Properties |
Sample |
Alloy |
Crush Rating |
Y (MPa) |
UTS (MPa) |
Elongation % |
A |
6063 |
1 |
231 |
252 |
14.0 |
A |
6063 |
1 |
226 |
252 |
13.5 |
|
|
|
|
|
|
B |
6XXX |
1 |
217 |
234 |
13.5 |
B |
6XXX |
1 |
214 |
233 |
13.5 |
|
|
|
|
|
|
C |
New |
1 |
215 |
235 |
13.5 |
C |
New |
1 |
209 |
229 |
13 |
[0018] The remaining Tables III and IV set forth the data obtained from the analysis of
extruded product samples produced using forced air quenching. All three alloys; the
6063, the 6063 type, and the alloy of this invention were extruded using a forced
air quench as described above. The extruded product samples were then aged to the
-T6 temper and evaluated using the static axial crush test, longitudinal tensile tests,
and test methods commonly used to indicate relative levels of fracture toughness,
corrosion resistance and formability. The relative fracture toughness of these materials
is indicated by comparing the unit propagation energy (UPE) values determined using
the Kahn tear test. The relative corrosion resistance of these materials is compared
through the use of bulk solution potential measurements. The relative formability
of these materials was evaluated using the Olsen dome test under dry and lubricated
conditions, and the guided bend test. The Olsen dome test is typically used to provide
an indication of relative formability in sheet products. In this instance samples
of the -T6 extrusion product were evaluated in the dry and lubricated conditions which
simulate plane strain and equal biaxial forming conditions. In this test, a dry or
lubricated punch is used to determine the dome height at which necking or failure
occurs in the material under evaluation with a higher value indicating better relative
formability. The guided bend test was originally developed to provide evaluation of
formability under conditions designed to simulate sheet forming operations. Typically
the samples evaluated represent -T4 sheet product that are given a 10% prestrain to
simulate deformation expected in drawing operations and are subsequently bent over
mandrels of different radii. Given the expected type of material deformation anticipated
in the service application for this extrusion product, strip samples were evaluated
in the -T6 condition and no prestrain was used. The desired outcome of this testing
is the ability to bend over a smaller mandrel without cracking; data from this evaluation
is typically expressed as a ratio of the limiting radius, R, over the thickness of
the sample, t. In this case, a smaller R/t ratio indicates better relative formability.
[0019] The resultant data as shown in Table III and Table IV demonstrates that the forced
air cooled aluminum alloy extrusions of 6063 and 6063 type materials demonstrated
reduced levels of performance in the static axial crush test (as compared to extrusions
that were subject to water quenching), while the new alloy of this invention maintained
desirable performance levels and demonstrated performance results similar to those
obtained on spray water quenched product. The aluminum alloy of this invention exhibits
improved toughness as indicated by the unit propagation energy, UPE, values measured
by the Kahn tear test with no adverse effect on strength. Typically in aluminum alloys,
as toughness increases it does so at the cost of strength. Bulk solution potential
measurements on these alloys are similar indicating that bulk corrosion performance
can be expected to be comparable. Comparison of the results of the formability indicator
tests illustrates that the tested extrusion of the alloy of the instant invention
demonstrated desired increases in the measured results from both the dry and lubricated
Olsen heights and a desired decrease in the guided bend radius achieved.
Table III
Forced Air Quenched |
Transverse Tensiles |
Longitudinal Tensiles |
45 Degree Tensiles |
Sample |
Alloy |
Y (MPa) |
UTS |
Elong. % |
Y (MPa) |
UTS |
Elong. % |
Y (MPa) |
UTS |
Elong. % |
Elong. % |
A |
6063 |
|
|
|
214 |
246 |
14.0 |
|
|
|
|
A |
6063 |
211 |
241 |
23.4 |
217 |
244 |
14.5 |
214 |
244 |
13.5 |
13 |
|
|
|
|
|
|
|
|
|
|
|
|
B |
6XXX |
|
|
|
219 |
241 |
13 |
|
|
|
|
B |
6XXX |
215 |
239 |
26.7 |
219 |
241 |
13.5 |
217 |
239 |
12 |
12 |
|
|
|
|
|
|
|
|
|
|
|
|
C |
New |
|
|
|
219 |
239 |
15 |
|
|
|
|
C |
New |
212 |
237 |
33.3 |
218 |
239 |
13 |
214 |
237 |
13.5 |
13 |
Table IV
Sample |
Alloy |
Crush Rating |
LT UPE (KJ/m^2) |
TL UPE (KJ/m^2) |
Solution Potential (mV v. SCE) |
Olsen Dry Avg. mm |
Olsen Wet Avg. mm |
Guided Bend R/t |
A |
6063 |
3 |
--- |
--- |
--- |
--- |
--- |
--- |
A |
6063 |
3 |
180.4 |
104.9 |
-0.756 |
0.2667 |
0.228 |
2.11 |
|
|
|
|
|
|
|
|
|
B |
6XXX |
3 |
--- |
--- |
--- |
--- |
--- |
--- |
B |
6XXX |
2 |
187.7 |
107.2 |
-0.776 |
0.255 |
0.272 |
2.34 |
|
|
|
|
|
|
|
|
|
C |
New |
1 |
--- |
--- |
--- |
--- |
--- |
--- |
C |
New |
1 |
236.1 |
179 |
-0.746 |
0.2957 |
0.3647 |
1.64 |
[0020] Comparison of the results obtained in the evaluation of the several materials described
in Table I is illustrated in the sole figure. Yield strength, fracture toughness,
and formability indicator results, represent the average of measurements collected
on the forced air cooled extrusion product samples. The data has been normalized with
respect to the 6063 product to allow comparison. It is to be appreciated that the
elimination of conventional water quench processing provides several distinct advantages.
The need for a complex water quenching distribution, delivery, and recovery system
is eliminated. The use of the air quench system increases the capacity to meet dimensional
tolerances that are often impaired by water quenching. The positive impact on cost
control and cost reduction occurs both in the extrusion processing stages and the
post-extrusion processing of the extruded component. Post extrusion manual calibration
of the extruded component is substantially reduced or even eliminated.
[0021] Unless indicated otherwise, the following definitions apply herein:
a. The term "ksi" is equivalent to kilopounds (1000 pounds) per square inch.
b. Percentages for a composition refer to % by weight.
c. The term "ingot-derived" means solidified from liquid metal by a known or subsequently
developed casting process rather than through powder metallurgy techniques. This term
shall include, but not be limited to, direct chill casting, electromagnetic casting,
spray casting and any variations thereof.
d. In stating a numerical range or a minimum or a maximum for an element of a composition
or a temperature or other process matter or any other matter herein, and apart from
and in addition to the customary rules for rounding off numbers, such is intended
to specifically designate and disclose each number, including each fraction and/or
decimal, (i) within and between the stated minimum and maximum for a range, or (ii)
at and above a stated minimum, or (iii) at and below a stated maximum. (For example,
a range of 1 to 10 discloses 1.1, 1.2...1.9, 2, 2.1, 2.2...and so on, up to 10, and
a range of 500 to 1000 discloses 501, 502...and so on, up to 1000, including every
number and fraction or decimal therewithin, and "up to 5" discloses 0.01...0.1...1
and so on up to 5.)
[0022] Having described the presently preferred embodiments, it is to be understood that
the invention may be otherwise embodied within the scope of the appended claims.
1. The method of producing an improved elongate aluminum alloy product comprising:
providing an alloy comprising essentially 0.45 to 0.7% magnesium, 0.35 to 0.6% silicon,
0.1 to 0.35% vanadium and 0.1 - 0.4% iron, the balance substantially aluminum and
incidental elements and impurities;
extruding a body of said alloy; and
quenching said body of said alloy.
2. The method according to claim 1, wherein said body of said alloy is air quenched or
water quenched.
3. The method according to claim 1, wherein the alloy contains 0.48 to 0.64% magnesium.
4. The method according to claim 1, wherein the alloy contains 0.4 to 0.5% silicon.
5. The method according to claim 1, wherein the alloy contains 0.2% vanadium.
6. The method according to claim 1, wherein the alloy contains 0.48 to 0.64% magnesium;
0.4 to 0.5% silicon; 0.2% vanadium and 0.2% iron.
7. The method according to claim 1, wherein said extruding is conducted with cylinder
temperatures from 371 to 538°C. (700° to 1000°F.), preferably 454 to 510°C. (850°
to 950°F.).
8. The method according to claim 1, wherein said quenching reduces the extruded product
temperature to from 121 to 232°C. (250° to 450°F.) or approximately 177°C. (350°F.)
or less.
9. The method according to claim 1, wherein said extruded product is stretched after
quenching.
10. The method according to claim 9, wherein the extruded product is straightened by an
amount equivalent to approximately 1.50%, or if desired by an amount equivalent to
approximately 0.25%.
11. The method according to any one of claims 1 to 10, which comprises:
heating said alloy;
extruding said alloy;
air quenching said extruded alloy;
artificially aging said extruded alloy.
12. The method according to any one of the preceding claims, wherein the extruded product
is a lineal frame member in a vehicle.
13. A product whose production includes the method according to any one of claims 1 to
12.
14. A vehicle frame comprising aluminum alloy extruded members joined to make a frame
or subassembly, at least a plurality of said aluminum extruded members comprising
aluminum alloy having the composition defined in any one of claims 1 to 6.