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Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444 (ISSN: 2141-7016)
440
Strength and Hardness of Directionally- Rolled AA1230 Aluminum Alloy
Samson Oluropo Adeosun; Wasiu Ajibola Ayoola;
Muideen Bodude; and Samuel Olujide Sanni
Department of Metallurgical and Materials Engineering,
University of Lagos, Akoka -Yaba, Lagos, Nigeria
Corresponding Author: Wasiu Ajibola Ayoola
___________________________________________________________________________ Abstract
There are processes that have been utilized to improve the tensile strength and hardness of aluminum alloys,
some of which include elemental and particle additions, since work hardening cannot be used to improve
strength and hardness of 1xxx wrought aluminum alloys. This work examines the possibility of introducing
secondary processing of transverse rolling after the initial primary rolling to strengthen and hardened wrought
aluminum alloy. The effects of transverse and longitudinal rolling on the tensile strength and hardness of
AA1230 aluminum alloy worked at ambient temperature (32 oC) have been studied. Samples were rolled in
longitudinal and transverse directions from thickness of 1.55 mm to 0.45 mm in 3-7 passes in two-high
irreversible mill. The samples rolled in transverse direction have hardness and tensile strength which are
superior to samples rolled in the longitudinal direction. The resultant crystals in transverse directions were
elongated in the rolling direction and agglomerate into larger crystals in this direction.
__________________________________________________________________________________________
Keywords: transverse direction, longitudinal direction, microstructures, hardness, tensile strength
________________________________________________________________________________________
*OME*CLATURE
1A 78 % deformation parallel to the rolling direction
1B 78 % deformation perpendicular to the rolling direction
2A 85 % deformation parallel to the rolling direction
2B 85 % deformation perpendicular to the rolling direction
3A 88 % deformation parallel to the rolling direction
3B 88 % deformation perpendicular to the rolling direction
4A 92 % deformation parallel to the rolling direction
4B 92 % deformation perpendicular to the rolling direction
5A 93 % deformation parallel to the rolling direction
5B 93 % deformation perpendicular to the rolling direction
6A 94 % deformation parallel to the rolling direction
6B 94% deformation perpendicular to the rolling direction
I*TRODUCTIO* Recent technological advancement in aerospace,
automotive, marine, construction and leisure
industries has made the demand for materials having
high strength to weight ratio, high specific modulus,
good corrosion resistance and good thermal
conductivity to be on the increase (Myer, 2002).
Aluminum and its alloys offer such combination of
tremendous properties. Aluminum 1230 alloy can be
manufactured into semi-finished or finished products
using techniques such as forging, rolling, welding,
casting e.t.c (Myer, 2002 and Polmear, 1995).The
mechanical properties of this alloy are better when
mechanically worked at temperatures below or above
it recrystallization temperature (Suraj, 2001; Zainul
2009; and Perovic, 1999). During cold working,
dislocation motions within metal matrix are restricted
resulting in strength increment as its shape is
changed. Structural components made from such
strengthened alloys are vital to the building,
aerospace and transportation industries, as well as for
the production of utensils for domestic use. Several
studies have been carried out on wrought aluminum
alloys (Ibrahim, 2007; Ming-xing et al, 2008; Sh
Ranjbar et al, 2010 and Lee et al, 2011) to understand
the effects of mechanical workings on its mechanical
properties. The effects of post rolling after the twist
extrusion process on commercially pure aluminum
were considered by Sh Ranjbar et al (2010). The
results show that both the hardness profile and bulk
strength were enhanced with post rolling. In addition,
the microstructural evolutions showed that post
rolling not only reduces the grain size but also
reduces the heterogeneity of microstructure across the
longitudinal section. Aluminum alloy sheets
fabricated by direct chill (DC) and continuous casting
(CC) routes were investigated by Lee et al, (2011).
The aluminum sheet produced through heavy cold-
rolling and recovery anneal exhibits highly
anisotropic tensile properties, and poor ductility at
45o from the rolling direction. This ductility was
attributed to the evolvement of intense shear bands
which is triggered by the yielding phenomenon in DC
specimens and less severe in CC. In both DC and CC
sheets, increasing strain rate enhance the strength and
also improved the ductility.
In this paper the effect of transverse and longitudinal
rolling on tensile strength and hardness of AA1230
aluminum alloy at ambient temperature are presented,
as a compliment to the results of post rolling effects
discussed by Sh Ranjbar et al (2010).
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444
© Scholarlink Research Institute Journals, 2011 (ISSN: 2141-7016)
jeteas.scholarlinkresearch.org
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444 (ISSN: 2141-7016)
441
EXPERIME*TAL PROCEDURE
Cold rolled aluminum 1230 sheet with thickness 7.20
mm used in this study was provided by Aluminum
Rolling Mills, Ota, Nigeria, and its nominal chemical
composition is given in Table 1.
Table 1: Chemical Composition of AA1230 Aluminum Alloy Sheet (Aluminum Rolling Mills, Ota, Nigeria,
2010)
Elements Fe Si Mn Zn Ti Pb Sn Mg Cu Al
Weight (%) 0.441 0.19 0.008 0.02 0.012 0.002 0.006 0.001 0.017 99.303
The sheet obtained from the rolling mills was blanked
into 20 x 20 x 7.20 mm samples and rolled at ambient
temperature (32 oC) in a two-high irreversible mill.
The thickness and percent reduction of the samples
produced are 1.55 mm (78 %), 1.08 mm (85 %), 0.85
mm (88 %), 0.60 mm (92 %), 0.47 mm (93 %) and
0.45 mm (94%) in accordance with ASTM E8-8ST
standard. These were produced in 3, 4, 5, 6, 7 and 7
passes, respectively, in both the longitudinal and
transverse directions (see nomenclature).
Hardness test was conducted by polishing each test
sample with emery papers down to 1000 mesh prior
to using the Webster hardness tester Model B. Ten
(10) measurements were taken for each sample and
the mean hardness determined. The mean hardness
values of the samples were converted to Rockwell
using Rockwell E scale. The tensile strengths of the
test samples were determined using a Monsanto
Tensometer in accordance with ASTM 1414
specifications. Samples were prepared for
metallographic examinations using Modern Wet-
grinding Machine. Four strips of 300 mm x 50 mm
emery paper (water proof base) were clamped, side
by side, on a sloping glass. The samples were then
pressed against the rotating paper with a stream of
water acting as coolant and particles remover. Coarse
grinding was done with emery papers of meshes 60,
240,320 followed by fine grinding with 600 and 800
meshes. The ground and polished samples were
etched in sodium hydroxide solution for 20 seconds.
The etched samples morphologies were examined
using a Digital Metallurgical Microscope at a
magnification of 100X.
The rolling process, tensile and hardness tests were
carried out using facilities at Aluminum Rolling Mills
Ota, Ogun State Nigeria while the microstructural
analysis was done at Metallurgical and Materials
Engineering laboratory of the University of Lagos,
Nigeria.
RESULTS A*D DISCUSSIO* Table 2 show the results of hardness and tensile tests
carried out on the samples. Increase in degrees of
deformation increases the hardness values from 52-
54Hv between 78-92 percent reduction and decreases
to 50 Hv between 92-94 percents reduction. During
cold rolling of wrought aluminum 1xxx alloy,
dislocation density increases as the degree of
deformation increases. Immobile dislocations are
created by the complicated network of interlocking
dislocations and this is responsible for its increase
work hardening rate resulting in hardness and
strength increment but with lost in ductility (Davis
and Oelmann, 1983) (see Figures 1-6). As
deformation processing increases from 93 to 94
percents more dislocations become mobile due to
unmerge of interlocking dislocations. This
eventually resulted in reduction in hardness and UTS
values of the alloy.
Figure 1 shows the stress-strain behaviour of the
samples at 78 % reduction in both the longitudinal
and transverse directions. The tensile strengths
response in these directions are linear and the same at
ε < 0.02. However, beyond this level, samples
strength in longitudinal direction surpasses that of the
transverse direction at the same strain up to 0.055
strain with ultimate tensile strength of 195.16 MPa.
However, sample deformed in the transverse
direction has superior UTS of 204.3 MPa. It should
be noted that the elongation responses are
independent of direction of rolling but the stress at
fracture depends on working direction.
In Figure 2, at 85 % reduction the strengths of the
alloy are higher in transverse than longitudinal
direction. At tensile strain of 0.05, UTS are almost
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444 (ISSN: 2141-7016)
442
equal (206.79 MPa-transverse and 206.22 MPa-
longitudinal) in both directions. The strains at
fracture are the same (0.068) and stress at fracture
very similar with negligible difference.
Samples deformed at 88 % show similar trend to that
at 85 % reduction (see Figure 3). The strains in the
deformation directions are similar at ε < 0.015. At ɛ >
0.02, the sample deformed in transverse direction
exhibited higher stresses.
Figure 4 show samples deformed at 92 % reduction
in both directions. Samples have slightly superior
strength in transverse direction than its longitudinal
direction at ε > 0.014.
In Figure 5, the deformed alloy at 93 % thickness
reduction possess similar strengths in both transverse
and longitudinal directions at 0 < ɛ ≤ 0.01. The
longitudinal direction deformed sample has UTS of
225 MPa (ɛ = 0.02), while UTS in the transverse
direction is slightly lower (220 MPa, ɛ = 0.03).
However, the elongation of the sample in the
transverse direction is superior (0.036) to that in the
longitudinal direction.
But, at 93 % thickness reduction (see Figure 5)
absence of structural homogeneity persists.
At 94 % thickness reduction, the sample morphology
indicates homogeneity in the texture of phases
precipitated. For ε ≤ 0.011, longitudinal and
transverse strengths responses are identical, but at
0.011 < ε < 0.017 stresses are higher in the
longitudinal direction than the transverse. However,
in the transverse direction UTS of 222.22 MPa is
achieved compared to 212.96 MPa in the longitudinal
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444 (ISSN: 2141-7016)
443
direction while the difference in samples’ elongations
with direction of deformation is negligible (Figure 6).
In this investigation, the strain at fracture decreases
as degree of deformation increases and it is
independent of test direction. The thickness reduction
at 78, 85, 88, 92, 93 and 94 percent produced
elongations of 7, 6.9, 5.3, 3.6 and 2.5 respectively in
the longitudinal direction and 7, 6.9, 4.8, 5.1, 3.5 and
2.4 respectively in the transverse direction. Thus
ductility of alloy decreases with degree of
deformation but does not differ appreciably with test
direction.
Table 2 Hardness and Ultimate Tensile Strength of
aluminum 1230 alloy with percent deformation (Authors
Computation, 2011)
Deformation (%)
Hardness
(HV)
Ultimate Tensile Strength (MPa)
Longitudinal A Transverse B
78
85
88
92
93
94
52
52
54
54
50
50
195.16
206.79
207.84
222.22
225.01
212.96
204.30
211.41
222.54
230.55
220.00
222.22
Plate 1a shows the microstructure of as-received
rolled sample. The matrix contains AlFeSi and α-
aluminum phases in approximately equal volume
fractions with other intermetallics predominately
FeAl3. The crystals of FeAl3 are finely dispersed
within the matrix phase while some of its crystals are
found at the grain boundaries. When the alloy sample
was deformed longitudinally with 78 % thickness
reduction, the α-aluminum and AlFeSi crystals
elongated along the deformation direction (see Plate
1b). The volume fraction of AlFeSi phase decline as
more crystals of FeAl3 are precipitated. But in the
transverse direction crystals of AlFeSi phase are
evenly distributed within the matrix, while crystals of
FeAl3 lie side by side with α-Al crystals (see Plate
2a).
Increase in thickness reduction from 78 to 85 %
across the rolling direction resulted in the dissolution
of FeAl3 crystals into the α-aluminum solvent (see
Plate 1c). The α-aluminum crystals are seen broken
up forming channel-like feature along the transverse
rolling direction. AlFeSi phase is still visible and its
crystals are finely distributed in the matrix.
Samples deformed at 85 % thickness reduction show
that deformation has significant effect on intensity,
distribution, orientation and volume fractions of the
phases present. In the rolling direction the intensity of
the FeAl3 phase decreased (see Plate 2b) when
compared with that deformed at 78 % thickness
reduction.
In transverse direction at 88 % thickness reduction
the alloy matrix contain needle-like crystals of the α-
Al phase with very fine crystals of FeAl3 (see Plate
1d) than those found in Plate 1c. Increase in degree of
deformation caused reduction in volume of AlFeSi
crystals that are precipitated. In Plate 2c, however,
deformation in longitudinal direction caused coarse
a b c
d e f
g Plate 1 Microstructure of rolling sample in the
longitudinal direction with thickness reduction.
(a) as-cast (b) 78 (c) 85 (d) 88 (e) 92 (f) 93 (g) 94
a b c
d e f Plate 2 Microstructure of rolling sample in the
transverse direction with thickness reduction
(a) 78 (b) 85 (c) 88 (d) 92 (e) 93 (f) 94
Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 2 (3): 440-444 (ISSN: 2141-7016)
444
formation of α-aluminum crystals and dissolution
into the matrix of some crystals of FeAl3 and AlFeSi
phases. The deformation also caused stretching of
AlFeSi crystals.
As deformation progresses to 92 % thickness
reduction, there is an increase in the amount of FeAl3
crystals in the matrix (Plate 1e). These crystals are
uniformly distributed with higher volume fraction to
sample tested in longitudinal direction (see Plate 2d).
It was observed in Plate 2d that the 92 % thickness
reduction in transverse direction causes fine
segregation of AlFeSi and elongation of crystals of
α-aluminum.
Plate 1f shows sample deformed in longitudinal
direction at 93 % thickness reduction. Crystals of
FeAl3 are absorbed by the α-Al matrix with
consequent increase in the volume fraction of α-
aluminum phase compared to that in Plate 2e. The
crystals of α-aluminum phase are seen stretched in
the deformation directions.
Further increase in degree of deformation in
longitudinal direction (94 %) enhanced uniform
distribution of all the three major phases precipitated
(see Plate 1g). The α-aluminum and AlFeSi phases
are fine and devoid of segregation. The effect of
rolling direction on the alignment and orientation of
the phases are negligible. However for sample rolled
at 94 % reduction in the longitudinal direction,
needle-like shaped crystals of α-aluminum are formed
within the matrix (see Plate 2f) while the volume
fraction of FeAl3 phase increase with decrease in
volume fraction of AlFeSi phase.
CO*CLUSIO*
This study has shown that before yielding at small
strains, the mechanical properties of 1230 aluminum
alloy are independent of deformation directions and
amount of reductions taken.
For alloy 1230, maximum hardness of 54 Hv can be
obtained at 92 % reduction and with superior strength
of 230 MPa in the transverse direction. Transverse
rolling of the alloy would be preferred as the
mechanical properties are unlikely to be
compromised.
Strain at fracture decreases as degree of deformation
increases and it is independent of test direction. The
ductility of this alloy decreases with degree of
deformation and does not differ appreciably with
direction of test.
REFERE*CES
Davis, D. J., and Oelmann, A., 1983, The Structure,
Properties and Heat Treatment of Metals. Piman
Books Limited.
Ibrahim, O., 2007 “A Study on the Re-solution Heat
Treatment of AA2618 Aluminum Alloy” Materials
Charaterisation, 58(3) 3, 312-317.
Lee, N. H., Chen, J.H., Kao, P.W., Tseng T.Y., and
Su, J.R., 2011, “Anisotropic Tensile Properties of
Recovery annealed Aluminum Alloy sheet” Materials
and Engineering A 528(4-5), 1979-1986.
Ming-xing G., Ming-pu W., Shen-fei C., Ruo-shan
L., and Shu-mei L., 2008 “ Effects of Cold Rolling of
Properties and Microstructures of Dispersion
Strengthened Copper Alloys” Trannsactions of
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Myer, K., 2002, Handbook of Materials Selection.
John Wily and Sons.
Perovic, A., Perovic, D.D., Weatherly, G.C., and
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AA6111 and AA6016” Scipta Materialia, 41(7), 703-
708.
Polmear, I.J., 1995, Light Alloys, Metallurgy of the
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Suraj, R., 2001 “Metal-Matrix Composites for Space
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Zainul, H., 2009 “Precipitation Strengthening and
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