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Citation: Pot, C.; Yazdani, M.;
Boyadjian, Q.; Bocher, P.; Béland, J.-F.
Texture and Mechanical Properties of
Extruded AA6063 Aluminum Alloy.
Eng. Proc. 2023,43, 25. https://
doi.org/10.3390/engproc2023043025
Academic Editor: Houshang
Alamdari
Published: 18 September 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
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4.0/).
Proceeding Paper
Texture and Mechanical Properties of Extruded AA6063
Aluminum Alloy †
Clément Pot 1, *, Majid Yazdani 1, Quentin Boyadjian 1, Philippe Bocher 1and Jean-François Béland 2
1Département de Génie Mécanique, École de Technologie Supérieure, 1100 Rue Notre-Dame Ouest,
Montréal, QC H3C 1K3, Canada; majid.yazdaniesmaeilabad.1@ens.etsmtl.ca (M.Y.);
quentin.boyadjian.1@ens.etsmtl.ca (Q.B.); philippe.bocher@etsmtl.ca (P.B.)
2
Conseil National de Recherches Canada, 501 Boulevard de l’UniversitéEst, Saguenay, QC G7H 8C3, Canada;
jean-francois.beland@cnrc-nrc.gc.ca
*Correspondence: clement.pot.2@ens.etsmtl.ca
†Presented at the 15th International Aluminium Conference, Québec, QC, Canada, 11–13 October 2023.
Abstract:
The extrusion process imposes a large amount of deformation on the material, resulting in
complex changes in microstructure morphology and crystallographic texture, making the predictions
of the final mechanical properties very challenging. In this research, the texture and the mechanical
properties of AA6063 aluminum extruded profiles are investigated. This alloy adopts a recrystallized
microstructure with equiaxed grains and a typical texture. The plastic anisotropy is compared with a
calculation method considering only the texture effect. Some attempts were made to numerically
reproduce specific experimental results by accounting for certain restauration mechanisms.
Keywords: extrusion; aluminum; texture; anisotropy; recrystallization
1. Introduction
Aluminum alloys are being widely used across various industry fields, including
automotive, railway vehicles construction, numerous airplane parts, among others. A
common objective in all these applications is the pursuit of materials with low density and
high strength, which enables the creation of lightweight and strong assemblies. Fortunately,
the aluminum extrusion process is well suited for achieving these goals, as the ductility of
aluminum alloys makes them good candidates for that shaping process.
Due to the high amount of plastic deformation encountered by the material during
extrusion, the microstructure of the extruded profiles is usually highly deformed or recrys-
tallized [
1
], which typically leads to plastic anisotropy in the microstructural characteristics.
The sources of anisotropy are not yet fully explained; some authors suggest that it only
depends on texture, while others consider that it results from the interaction among texture,
precipitates, grain shapes and dislocations, or some combination of these factors [
2
]. To
describe the plastic anisotropy of materials, the Lankford coefficient, also known as R-value,
has been a very useful tool [
3
], as it provides an indication of the primary deformation
directions that a part experiences with specific types of loading.
The alloy investigated in this study is AA6063, a commercially available and widely used
alloy in the extrusion industry. It is characterized by a recrystallized microstructure [
4
,
5
] with
equiaxed grains and a typical texture that emerges as a result of this recovery process, such
as the Cube texture and components derived from Goss and Brass. Previous studies have
reported that extruded 6063 alloy profiles typically exhibit diverse texture characteristics,
primarily influenced by their position along the normal direction (ND), indicating different
thermo-mechanical histories based on their location within the material. It has been found
that the edges are dominated by Brass, S and Brass-derived components, which are typical
of recrystallized structures. In contrast, the center is richer in Cube and random components,
Eng. Proc. 2023,43, 25. https://doi.org/10.3390/engproc2023043025 https://www.mdpi.com/journal/engproc
Eng. Proc. 2023,43, 25 2 of 10
indicating the occurrence of recovery processes. Additionally, a thin zone separates the
center and edges, exhibiting a strong Goss component resulting from recrystallization [5].
2. Materials and Methods
2.1. Materials and Characterisation
This study focuses on AA6063, which is frequently used in the industry and formed
with the extrusion process. The composition is provided in Table 1. After DC casting, 4-inch
OD billets were homogenized with a standard cycle prior to extrusion, which produced
rectangular tubes with an extrusion ratio of 25. The extrusion process was carried out at a
speed of 8 mm
·
s
−1
, and an average exit temperature of 535
◦
C was reached. The samples
were investigated in as-extruded condition.
Table 1. Chemical composition of the tested alloy.
Alloy Mg Si Cu Mn Cr Fe Al
AA6063 0.49 0.44 0.01 0.03 0.00 0.18 Bal.
Prior to measuring their textures, the samples were mirror-polished using SiC griding
paper and then electropolished at 30 V for 60 s following the ASTM E1558 standard
electrolyte for Al-alloys with the following composition: 800 mL of ethanol, 140 mL of
distilled water and 60 mL of perchloric acid.
The textures were measured with the electron backscatter diffraction (EBSD) technique
with a Hitachi SU-70 field emission gun scanning electron microscope. The obtained results
were analyzed using ATEX [
6
] and in-house Python code developed for generating texture
plots and performing calculations. The list of texture components used to characterize the
crystallographic orientations is provided below in Table 2, and orientations are classified
with a 12◦misorientation angle.
Table 2. List of the texture components used in this work.
Texture Component Euler Angles (ϕ1,φ,ϕ2) Miller Indices
Cube (0, 0, 0) {001}<100 >
Rotated Cube (0, 0, 45) {001}<110 >
Brass (35, 45, 0) {011}<211 >
Brass 2 (145, 45, 0) {011}<211 >
Goss (0, 45, 0) {011}<100 >
Rotated-Goss (90, 45, 0) {011}<011 >
Goss/Brass (35, 90, 45) {110}<111 >
Goss/Brass 2 (145, 90, 45) {110}<111 >
Copper (90, 35, 45) {112}<111 >
Copper 2 (270, 35, 45) {112}<111 >
A (0, 35, 45) {112}<110 >
A(180, 35, 45) {112}<110 >
Inverse Brass (0, 55, 45) {111}<110 >
Inverse Copper (30, 55, 45) {111}<121 >
Brass-R (90, 55, 45) {111}<112 >
E (60, 55, 45) {111}<011 >
S1 (61, 34, 64) {213}<364 >
S2 (241, 34, 64) {213}<364 >
S3 (299, 34, 26) {123}<634 >
S4 (119, 34, 26) {123}<634 >
2.2. Mechanical Characterisation
Microtensile tests were conducted using a 5000 N tensile/compression module from
Kammrath & Weiss GmbH (Schwerte, Germany). The dimensions of the tensile specimens
Eng. Proc. 2023,43, 25 3 of 10
were selected according to the ASTM E8 standard and are illustrated in Figure 1. The
samples were machined from the larger side of an extruded tube at various angles between
the extrusion direction and the sample direction. Angles of 0, 22.5, 45, 67.5 and 90 degrees
were tested, as shown in Figure 2, which displays the placement of the tensile samples
within an extruded rectangular tube (5 and 10 degrees were not studied).
Eng. Proc. 2023, 43, x 3 of 10
2.2. Mechanical Characterisation
Microtensile tests were conducted using a 5000 N tensile/compression module from
Kammrath & Weiss GmbH (Schwerte, Germany). The dimensions of the tensile specimens
were selected according to the ASTM E8 standard and are illustrated in Figure 1. The sam-
ples were machined from the larger side of an extruded tube at various angles between the
extrusion direction and the sample direction. Angles of 0, 22.5, 45, 67.5 and 90 degrees were
tested, as shown in Figure 2, which displays the placement of the tensile samples within an
extruded rectangular tube (5 and 10 degrees were not studied).
The deformation fields were calculated using a digital image correlation technique,
implemented in open source software called OpenDIC [7].
Figure 1. Microtensile specimen according to ASTM E8 standard, dimensions in millimeters.
Figure 2. Machining plan of the microtensile specimens from an extruded tubular profile. ED: ex-
trusion direction; TD: transverse direction. Recto and Verso are the larger sides of the extruded
tubes.
3. Results
3.1. Microstructure of the Extruded Samples
The microstructure of the AA6063 samples was investigated, and the results are
shown in Figure 3. In Figure 3a, the EBSD map of the full thickness is presented, clearly
showing that the grains at the upper and lower edges have different orientations com-
pared with the center. The texture of the whole thickness is given in Figure 3b with the
{111} pole figure. Additionally, Figure 3c displays the pole figure (PF) of the upper edge;
Figure 3d shows the center PF; Figure 3e the lower-edge PF. They clearly show that the
texture in the center of the sample is different compared with the edges. The whole thick-
ness is dominated by Cube and Rotated Cube (13.3% and 9.2%, respectively) with small
amounts of S, Goss/Brass and E components. This is related to the high proportion of
Cube-related components at the center (16.6% for Cube and 11.3% for Rotated Cube). At
the upper edge, the Goss/Brass 1 component is the most present, with 11.9%, followed by
S, with 5.8%. At the lower edge, 4.0% and 8.5% of Goss/Brass components, 7.4% of Brass 2
and 4.6% of S can be found. A few remarks can be made regarding all these PFs. Firstly, it
can be observed that the Cube orientations are clearly visible in Figure 3b,d, but there is
no distinct paern discernible in Figure 3c,e. Moreover, the texture index (TI) is not as
high as for textured polycrystals, indicating that a significant proportion consists of ran-
domly oriented grains, representing roughly 60% of the grains in all zones of the sample
(the last row of the table in Figure 3 accounts for orientations that are not solely random
orientations).
Figure 1. Microtensile specimen according to ASTM E8 standard, dimensions in millimeters.
Eng. Proc. 2023, 43, x 3 of 10
2.2. Mechanical Characterisation
Microtensile tests were conducted using a 5000 N tensile/compression module from
Kammrath & Weiss GmbH (Schwerte, Germany). The dimensions of the tensile specimens
were selected according to the ASTM E8 standard and are illustrated in Figure 1. The sam-
ples were machined from the larger side of an extruded tube at various angles between the
extrusion direction and the sample direction. Angles of 0, 22.5, 45, 67.5 and 90 degrees were
tested, as shown in Figure 2, which displays the placement of the tensile samples within an
extruded rectangular tube (5 and 10 degrees were not studied).
The deformation fields were calculated using a digital image correlation technique,
implemented in open source software called OpenDIC [7].
Figure 1. Microtensile specimen according to ASTM E8 standard, dimensions in millimeters.
Figure 2. Machining plan of the microtensile specimens from an extruded tubular profile. ED: ex-
trusion direction; TD: transverse direction. Recto and Verso are the larger sides of the extruded
tubes.
3. Results
3.1. Microstructure of the Extruded Samples
The microstructure of the AA6063 samples was investigated, and the results are
shown in Figure 3. In Figure 3a, the EBSD map of the full thickness is presented, clearly
showing that the grains at the upper and lower edges have different orientations com-
pared with the center. The texture of the whole thickness is given in Figure 3b with the
{111} pole figure. Additionally, Figure 3c displays the pole figure (PF) of the upper edge;
Figure 3d shows the center PF; Figure 3e the lower-edge PF. They clearly show that the
texture in the center of the sample is different compared with the edges. The whole thick-
ness is dominated by Cube and Rotated Cube (13.3% and 9.2%, respectively) with small
amounts of S, Goss/Brass and E components. This is related to the high proportion of
Cube-related components at the center (16.6% for Cube and 11.3% for Rotated Cube). At
the upper edge, the Goss/Brass 1 component is the most present, with 11.9%, followed by
S, with 5.8%. At the lower edge, 4.0% and 8.5% of Goss/Brass components, 7.4% of Brass 2
and 4.6% of S can be found. A few remarks can be made regarding all these PFs. Firstly, it
can be observed that the Cube orientations are clearly visible in Figure 3b,d, but there is
no distinct paern discernible in Figure 3c,e. Moreover, the texture index (TI) is not as
high as for textured polycrystals, indicating that a significant proportion consists of ran-
domly oriented grains, representing roughly 60% of the grains in all zones of the sample
(the last row of the table in Figure 3 accounts for orientations that are not solely random
orientations).
Figure 2.
Machining plan of the microtensile specimens from an extruded tubular profile. ED:
extrusion direction; TD: transverse direction. Recto and Verso are the larger sides of the extruded
tubes.
The deformation fields were calculated using a digital image correlation technique,
implemented in open source software called OpenDIC [7].
3. Results
3.1. Microstructure of the Extruded Samples
The microstructure of the AA6063 samples was investigated, and the results are shown
in Figure 3. In Figure 3a, the EBSD map of the full thickness is presented, clearly showing
that the grains at the upper and lower edges have different orientations compared with
the center. The texture of the whole thickness is given in Figure 3b with the {111} pole
figure. Additionally, Figure 3c displays the pole figure (PF) of the upper edge; Figure 3d
shows the center PF; Figure 3e the lower-edge PF. They clearly show that the texture in
the center of the sample is different compared with the edges. The whole thickness is
dominated by Cube and Rotated Cube (13.3% and 9.2%, respectively) with small amounts
of S, Goss/Brass and E components. This is related to the high proportion of Cube-related
components at the center (16.6% for Cube and 11.3% for Rotated Cube). At the upper edge,
the Goss/Brass 1 component is the most present, with 11.9%, followed by S, with 5.8%. At
the lower edge, 4.0% and 8.5% of Goss/Brass components, 7.4% of Brass 2 and 4.6% of S can
be found. A few remarks can be made regarding all these PFs. Firstly, it can be observed
that the Cube orientations are clearly visible in Figure 3b,d, but there is no distinct pattern
discernible in Figure 3c,e. Moreover, the texture index (TI) is not as high as for textured
polycrystals, indicating that a significant proportion consists of randomly oriented grains,
representing roughly 60% of the grains in all zones of the sample (the last row of the table
in Figure 3accounts for orientations that are not solely random orientations).
Eng. Proc. 2023,43, 25 4 of 10
Eng. Proc. 2023, 43, x 4 of 10
Figure 3. Microstructure of the full thickness of an AA6063 extruded tube on the larger side. The
EBSD map is given in the ND-TD plane in (a), and pole figures are given as follows: (b) full thick-
ness, (c) upper edge, (d) center, (e) lower edge. The table provides the volumetric fraction of each
texture component (including only the most important ones).
Figure 4 highlights different data: In Figure 4a, a map of the grain boundary angles
is shown, revealing that the majority of the grain boundaries (79.1%) are classified as high-
angle grain boundaries (HAGBs), with angles ranging from 15 to 63.5 degrees, in as-ex-
truded condition, which is typical of a non-deformed or fully recovered state. In both Fig-
ure 4a,b, it is evident that most of the grains exhibit an equiaxed morphology, except at
the upper edge, where they appear to be elongated in the ND (perpendicular to the edge).
In Figure 4b, the grain size is depicted for a total of 1193 grains, showing smaller grains in
the center compared with the edges. The grain size distribution is indicated below in Fig-
ure 4b, with an average size of 140 µm (160 µm at the upper and lower edges and 110 µm
at the center).
Figure 4. (a) Misorientation angle of the grain boundaries and (b) grain size distribution of an es-
extruded sample, all seen in the ND-TD plane.
Figure 3.
Microstructure of the full thickness of an AA6063 extruded tube on the larger side. The
EBSD map is given in the ND-TD plane in (
a
), and pole figures are given as follows: (
b
) full thickness,
(
c
) upper edge, (
d
) center, (
e
) lower edge. The table provides the volumetric fraction of each texture
component (including only the most important ones).
Figure 4highlights different data: In Figure 4a, a map of the grain boundary angles
is shown, revealing that the majority of the grain boundaries (79.1%) are classified as
high-angle grain boundaries (HAGBs), with angles ranging from 15 to 63.5 degrees, in
as-extruded condition, which is typical of a non-deformed or fully recovered state. In both
Figure 4a,b, it is evident that most of the grains exhibit an equiaxed morphology, except
at the upper edge, where they appear to be elongated in the ND (perpendicular to the
edge). In Figure 4b, the grain size is depicted for a total of 1193 grains, showing smaller
grains in the center compared with the edges. The grain size distribution is indicated below
in Figure 4b, with an average size of 140
µ
m (160
µ
m at the upper and lower edges and
110 µm at the center).
Eng. Proc. 2023, 43, x 4 of 10
Figure 3. Microstructure of the full thickness of an AA6063 extruded tube on the larger side. The
EBSD map is given in the ND-TD plane in (a), and pole figures are given as follows: (b) full thick-
ness, (c) upper edge, (d) center, (e) lower edge. The table provides the volumetric fraction of each
texture component (including only the most important ones).
Figure 4 highlights different data: In Figure 4a, a map of the grain boundary angles
is shown, revealing that the majority of the grain boundaries (79.1%) are classified as high-
angle grain boundaries (HAGBs), with angles ranging from 15 to 63.5 degrees, in as-ex-
truded condition, which is typical of a non-deformed or fully recovered state. In both Fig-
ure 4a,b, it is evident that most of the grains exhibit an equiaxed morphology, except at
the upper edge, where they appear to be elongated in the ND (perpendicular to the edge).
In Figure 4b, the grain size is depicted for a total of 1193 grains, showing smaller grains in
the center compared with the edges. The grain size distribution is indicated below in Fig-
ure 4b, with an average size of 140 µm (160 µm at the upper and lower edges and 110 µm
at the center).
Figure 4. (a) Misorientation angle of the grain boundaries and (b) grain size distribution of an es-
extruded sample, all seen in the ND-TD plane.
Figure 4.
(
a
) Misorientation angle of the grain boundaries and (
b
) grain size distribution of an
es-extruded sample, all seen in the ND-TD plane.
Eng. Proc. 2023,43, 25 5 of 10
The same analysis was conducted on a 25%-deformed sample that was elongated in
the ED (necking had already occurred). This sample was extracted from a region nearby
that of the previous sample illustrated in Figure 3. The results are presented in Figure 5,
where an EBSD map once again reveals the presence of these distinct orientations at the
upper and lower edges compared with the center. This information is further supported
by the PFs given in Figure 5b (full thickness), Figure 5c (upper edge), Figure 5d (center)
and Figure 5e (lower edge). This map also reveals the presence of several large grains,
which are colored in various shades. The table indicates the continued presence of strong
Cube-related textures in the deformed sample, since there are 12.8% of Cube and 5.7%
of Rotated-Cube textures and the center exhibits higher Cube (16.5%) and Rotated-Cube
(6.1%) textures. These components are less prevalent at the edges of this sample, with only
5.6% at the upper edge and 3.0% at the lower one. Instead, the most significant components
are S and, particularly, E for the upper edge. Additionally, a few observations can be made
about the PFs. Firstly, similarly to Figure 3, the Cube texture pattern is clearly visible in
Figure 5b,d, while no clear pattern can be observed in Figure 5c,e. Secondly, the TI is
also not as high as that of textured polycrystals, revealing a strong proportion of random
orientations, as indicated in the last line of the table in Figure 4.
Figure 5.
Microstructure of the full thickness of a sample extracted from the larger side of a tube,
after undergoing 25% of elongation in the ED. The EBSD map is given in the ND-TD plane in (
a
),
and pole figures are given as follows: (
b
) full thickness, (
c
) upper edge, (
d
) center, (
e
) lower edge.
The table provides the volumetric fraction of each texture component (including only the most
important ones).
Two maps are displayed in Figure 6. In Figure 6a, the grain boundary angles are
shown, revealing a significant presence of low-angle grain boundaries (LAGBs) in many
grains. This is a characteristic feature of highly deformed aluminum alloys. This type of
grain boundaries represents 68.4% of the total boundaries compared with only 20.3% of
HAGBs. Additionally, there is a small number of grains that are not highly concentrated at
LAGBs, particularly at the edges. In Figure 6b, the grain size distribution is represented
over 893 grains, revealing that the majority of the grains are also equiaxed, with smaller
grains at the center. It is also noticeable that the upper edge exhibits grain shapes similar to
those described in Figure 4.
Eng. Proc. 2023,43, 25 6 of 10
Eng. Proc. 2023, 43, x 6 of 10
Figure 6. (a) Misorientation angle of the grain boundaries and (b) grain size distribution after 25%
of deformation in the ED, all given in the ND-TD plane.
3.2. Mechanical Properties and Anisotropy
The tensile tests conducted on the samples clearly revealed the presence of anisot-
ropy in the mechanical behavior. Figure 7 presents the resulting true stress/true strain
curves for 0, 22.5, 45, 67.5 and 90° between the ED and the tensile direction. The 90°-ori-
ented samples (parallel to the TD) presented higher ultimate strength and higher total
strain at necking. It is interesting to see that all the curves have very close behaviors, with
the highest ultimate strength for the 90° samples and the lowest value for the 0° samples.
A synthesis of the mechanical properties is given below in Table 3, displaying the close
yield and ultimate strength for all orientations.
Figure 7. True stress/true strain curves for AA6063 as-extruded samples for several orientations.
Figure 6.
(
a
) Misorientation angle of the grain boundaries and (
b
) grain size distribution after 25% of
deformation in the ED, all given in the ND-TD plane.
3.2. Mechanical Properties and Anisotropy
The tensile tests conducted on the samples clearly revealed the presence of anisotropy
in the mechanical behavior. Figure 7presents the resulting true stress/true strain curves for
0, 22.5, 45, 67.5 and 90
◦
between the ED and the tensile direction. The 90
◦
-oriented samples
(parallel to the TD) presented higher ultimate strength and higher total strain at necking. It
is interesting to see that all the curves have very close behaviors, with the highest ultimate
strength for the 90
◦
samples and the lowest value for the 0
◦
samples. A synthesis of the
mechanical properties is given below in Table 3, displaying the close yield and ultimate
strength for all orientations.
Eng. Proc. 2023, 43, x 6 of 10
Figure 6. (a) Misorientation angle of the grain boundaries and (b) grain size distribution after 25%
of deformation in the ED, all given in the ND-TD plane.
3.2. Mechanical Properties and Anisotropy
The tensile tests conducted on the samples clearly revealed the presence of anisot-
ropy in the mechanical behavior. Figure 7 presents the resulting true stress/true strain
curves for 0, 22.5, 45, 67.5 and 90° between the ED and the tensile direction. The 90°-ori-
ented samples (parallel to the TD) presented higher ultimate strength and higher total
strain at necking. It is interesting to see that all the curves have very close behaviors, with
the highest ultimate strength for the 90° samples and the lowest value for the 0° samples.
A synthesis of the mechanical properties is given below in Table 3, displaying the close
yield and ultimate strength for all orientations.
Figure 7. True stress/true strain curves for AA6063 as-extruded samples for several orientations.
Figure 7. True stress/true strain curves for AA6063 as-extruded samples for several orientations.
Eng. Proc. 2023,43, 25 7 of 10
Table 3.
Young’s modulus, yield strength and ultimate strength of representative samples from the
test campaign.
Alloy 0◦22.5◦45 67.5◦90
E (GPa) 71.2 65.2 66.6 62 59.2
Ys(MPa) 76 78 77 74 71
Us(MPa) 247 253 257 252 258
The Lankford coefficients as a function of tensile elongation are shown in Figure 8.
Surprisingly, although the stress/strain curves exhibit similar behavior for most of the
samples, the R-value measurements reveal significant variations among them. For most of
the samples, the R-value undergoes a variable phase in the elastic region before reaching a
relatively constant value during the strain-hardening phase, except for the 90
◦
-oriented
samples. These samples have the lowest anisotropy in the early stages of deformation
(considering the R = 1 behavior to be perfectly isotropic), which gradually increases with
the deformation level. The sample oriented at a 22.5
◦
angle displays the highest degree of
anisotropy among all the tested samples.
Eng. Proc. 2023, 43, x 7 of 10
Tab le 3 . Young’s modulus, yield strength and ultimate strength of representative samples from the
test campaign.
Alloy 0° 22.5° 45 67.5° 90
E (GPa) 71.2 65.2 66.6 62 59.2
Y
s
(MPa) 76 78 77 74 71
U
s
(MPa) 247 253 257 252 258
The Lankford coefficients as a function of tensile elongation are shown in Figure 8.
Surprisingly, although the stress/strain curves exhibit similar behavior for most of the
samples, the R-value measurements reveal significant variations among them. For most of
the samples, the R-value undergoes a variable phase in the elastic region before reaching
a relatively constant value during the strain-hardening phase, except for the 90°-oriented
samples. These samples have the lowest anisotropy in the early stages of deformation
(considering the R = 1 behavior to be perfectly isotropic), which gradually increases with
the deformation level. The sample oriented at a 22.5° angle displays the highest degree of
anisotropy among all the tested samples.
Figure 8. Lankford coefficient curves for as-extruded samples of AA6063 for different orientations.
4. Discussion
4.1. Microstructure of the as-Extruded Samples
The as-extruded samples exhibit high proportions of Cube and Rotated Cube, ac-
counting for 13.3% and 9.2%, respectively. These proportions are higher at the center, and
a large fraction of S and Brass-derived components (Goss/Brass 1 and 2, and Brass 2) are
observed at the upper and lower edges. These findings are consistent with the results re-
ported by Araki et al. [4,5]. The results of their study show slight differences, since they
found 20–30% of Cube, 9–13% of Goss and 4–6% of S textures in the whole section of the
extruded profiles, in contrast with the 22.5% of various Cube, 3.1% of Brass-like and 2.9%
of S textures observed in our profiles. These differences in texture composition can be at-
tributed to variations in extrusion parameters and the dissimilar shape of the final prod-
uct, resulting in different strain paths and levels experienced by the material, which in
turn affect the recrystallisation and recovery capacities of the grains. The measured
Figure 8. Lankford coefficient curves for as-extruded samples of AA6063 for different orientations.
4. Discussion
4.1. Microstructure of the as-Extruded Samples
The as-extruded samples exhibit high proportions of Cube and Rotated Cube, account-
ing for 13.3% and 9.2%, respectively. These proportions are higher at the center, and a
large fraction of S and Brass-derived components (Goss/Brass 1 and 2, and Brass 2) are
observed at the upper and lower edges. These findings are consistent with the results
reported by Araki et al. [
4
,
5
]. The results of their study show slight differences, since they
found 20–30% of Cube, 9–13% of Goss and 4–6% of S textures in the whole section of
the extruded profiles, in contrast with the 22.5% of various Cube, 3.1% of Brass-like and
2.9% of S textures observed in our profiles. These differences in texture composition can
be attributed to variations in extrusion parameters and the dissimilar shape of the final
product, resulting in different strain paths and levels experienced by the material, which
in turn affect the recrystallisation and recovery capacities of the grains. The measured
fractions of texture components in the as-extruded samples are typical of fully recrystallized
material, particularly for Cube-related components, which is attributed to the forming
Eng. Proc. 2023,43, 25 8 of 10
process and the alloy itself, which possesses a high recrystallization capacity. In addition,
the average grain size of the full thickness in our study is higher compared with the range of
75–98 microns reported by Araki et al. [
4
,
5
]. The particularly high grain sizes observed in
our study further support the notion that the alloy is in a fully recrystallized/recovered
state. Considering their shape in the upper-edge region, in Figure 4, suggests that the grains
in this region have grown from the edge, indicating a different energy state compared with
the center. This difference may have been induced by various deformation paths/levels
and needs further investigations.
Nevertheless, the noticeable differences in the proportions of texture components
between the edges and the center indicate that the recrystallization process may have
occurred differently along the thickness of the sample. According to the literature [
5
], it
is suggested that recovery processes primarily occur at the center of the sample, while
recrystallization takes place at the edges [
5
]. This difference in thermal history along the
sample thickness could come from the different strain paths encountered by the material
during the extrusion process but could also be due to the high shear rate imposed on
the edges when the material goes through the extrusion die. Considering the fact that
recrystallization is driven by the stored energy inside the material, higher deformation and
shear levels along the edges could induce high amounts of stored energy, locally modifying
the texture compared with the center [8].
4.2. Microstructure of the Samples Deformed in the ED
The 25% deformation in the ED results in a change in the textures of the samples.
According to Figures 3and 5, it appears that the fraction of Cube orientation is not sig-
nificantly affected by deformation (changing from 13.3% to 12.8% for the whole sample,
from 16.6% to 16.5% at the center, below 1% at the upper edge and from 1.6 to 2.1% at the
lower edge). The slightly different fractions can be attributed to the fact that the studied
samples were not extracted from the same place. Regarding the Rotated Cube texture, this
texture component appears to be relatively unaffected by the deformation at the edges,
as its fraction goes from 5.2% to 4.7% at the upper edge and from 0.0% to 0.9% at the
lower edge. However, a decrease in the fraction of this component is observed at the
center, dropping from 11.3% to 6.1%. This reduction is also evident for the Goss/Brass
1 and 2, and Brass 2 components for the whole sample. This decrease is in favor of an
increase in the E component (rising from 3.6% to 6.0% in the overall sample), as well as
Copper-related components (Copper and Copper 2, particularly present at the upper edge
with fractions of 3.6% and 4.5%, respectively), and of the emergence of Inverse Brass, which
is characteristic of deformed textured materials. This confirms the typical results observed
in plastically deformed aluminum alloys. Furthermore, the EBSD map in Figure 5a reveals
the presence of several large grains scattered throughout the entire thickness, exhibiting a
diverse range of colors. These grains display a high density of LAGBs (2–5
◦
and 5–15
◦
), as
shown in Figure 6a, which suggests that they have been divided into subgrains, which is
characteristic of a strain-hardened microstructure.
Furthermore, the grains oriented in the [111]//ED (indicated by the blue color in
Figure 5a), which is along the loading direction, exhibit the lowest density of LAGBs, as
shown in Figure 6a. It highlights the fact that these grains are less favorably oriented to be
deformed during a tensile test, since the preferred slip direction in FCC-structured alloys is
[110]. These grains are mainly located at the upper edge, but they are also present at the
center and lower edge with lower occurrence.
Therefore, it is important to note that a source of anisotropy could come from the
different grain textures and shapes at the edges. This is supported by lower LAGB density
in these regions, as observed in Figure 6a. As a result, this leads to distinct mechanical
behaviors in different zones of the sample, resulting in different deformation states between
the center and the edges, especially considering the variable angle between the loading
direction and the ED.
Eng. Proc. 2023,43, 25 9 of 10
4.3. Anisotropy of the Samples
The mechanical response of the ED-, 22.5
◦
-, 45
◦
-, 67.5
◦
- and TD-oriented samples can
be attributed to their fully recrystallized state. The results do align with the ones reported in
the literature, which typically show similar behaviors for all orientations in a recrystallized
state [3], which is attributed to the high fraction of randomly oriented grains.
The R-value curves also require further investigation, as they do not display the same
trend that is commonly observed. Typically, a minimum value is encountered in the 45
◦
orientation (around 5% deformation), and all the measured values are slightly lower com-
pared with the expected values reported in the literature. However, it is important to note
that the literature results usually involve alloys that do not exhibit various microstructural
characteristics, with the presence of distinct textures near the edges of the samples. This
may contribute to the observed divergences in the R-value. Further EBSD investigations in
the 45
◦
direction are required to study the grain orientations, which would likely provide
valuable data on the orientations of slip plans in this direction.
5. Conclusions
This study investigated the microstructural characteristics of as-extruded AA6063
profiles. The material exhibited a fully recrystallized state, characterized by equiaxed grains,
strong Cube and Rotated-Cube textures and significant density of HAGBs. Microstructural
observations revealed that the grains at the edges displayed different shapes and textures
compared with those at the center. This can be attributed to variations in the deformation
path and level during extrusion, which contribute to the development of an anisotropic
behavior during subsequent deformation processes. The tensile tests revealed similar
mechanical response for all orientations. The calculation of the Lankford coefficients
revealed a constant value in the strain-hardening region, with the 22.5
◦
-oriented samples
exhibiting the lowest coefficient and the TD-oriented ones having the highest coefficients.
The tensile deformation resulted in a decrease in the fractions of Rotated-Cube and Brass-
derived components, while there was an increase in the fractions of E and Copper-related
components. However, this behavior varied depending on the zone investigated within
the sample. The formation of LAGBs and variations in texture components did not occur in
the same manner at the upper and lower edges compared with the center after a tensile test
along the ED. The center region displayed higher density of LAGBs compared with the
other regions, supporting the hypothesis that different zones of the material influence its
macroscopic mechanical behavior.
Author Contributions:
Conceptualization, C.P., M.Y., Q.B. and P.B.; methodology, C.P., M.Y., Q.B.,
J.-F.B. and P.B.; software, C.P. and Q.B.; validation, Q.B., P.B. and J.-F.B.; writing—review and editing,
C.P., Q.B., M.Y. and P.B.; supervision, P.B.; funding acquisition, P.B. All authors have read and agreed
to the published version of the manuscript.
Funding:
The APC was funded by National Research Council and Natural Sciences and Engineering
Research Council Canada.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is
not applicable to this article.
Acknowledgments:
The authors are grateful to NRC Canada and Rio Tinto for their
technical support.
Conflicts of Interest: The authors declare no conflict of interest.
Eng. Proc. 2023,43, 25 10 of 10
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