Journal of Materials and Metallurgical Engineering
ISSN: 2231-3818 (online), ISSN: 2321-4236 (print)
Volume 4, Issue 2
www.stmjournals.com
A Study of Improvement of Mechanical Properties
of Aluminum by Conventional Casing
and Deformation Process
Hafiz Abdul Ahad Qazi*
Mehran University of Engineering and Technology, Jamshoro, Pakistan
Abstract
Nowadays, Aluminum-Zinc alloy system are the major and rapid development in the field
of automotive and aerospace industries for growing demand of efficient vehicles and
aircrafts to reduce energy consumption and air pollution. Aluminum is a very soft metal
by nature. Different alloying elements were added in the past to increase its strength and
toughness. Zinc is considered as a major alloying element in aluminum to increase its
strength and toughness. Present experimental work was conducted to determine the
appropriate amount of zinc to be added in pure aluminum to increase its mechanical
properties. A wide range of experimental work was conducted on pure aluminum to
determine the appropriate amount of zinc to be added to develop Al-Zn alloy using
conventional foundry method. Pure aluminum was mixed with different percentages of
zinc with constant percentage of magnesium and copper. The molten alloys were cast in
metal mold. Wrought alloys have high strength as compared to cast alloy so after casting,
the alloy was subjected to mechanical rolling. Standard samples were prepared for
tensile tests and a number of samples were age hardened. Various characterization
techniques were used to investigate the chemical composition, tensile strength, ductility
(elongation), and hardness. It has been observed that the alloy containing 5% Zn and 2%
Mg, gives highest strength, and have good ductility in heat-treated condition.
Keywords: Aluminum-Zinc alloy, foundry method, mechanical rolling
*Author for Correspondence E-mail: ahadqazi10@yahoo.com
INTRODUCTION
Aluminum-Zinc (Al-Zn) alloys are the major
and rapid development in the field of
metallurgy in recent years especially in
nonferrous metallurgy. Al-Zn alloys are
widely used for many engineering applications
such as in automobile and aerospace industries
due to its attractive physical as well as
mechanical properties such as strength to
weight ratio.
purpose aluminum and its additional required
materials were purchased from the local
market. The material was developed and
characterized at the Department of Metallurgy
& Materials Engineering, MUET, Jamshoro,
Pakistan.
One of the major issues concerned with the
development of Al-Zn alloy system is the
appropriate amount of its alloying elementzinc. There is continuous demand to determine
the appropriate amount of alloying element
zinc which is added in pure aluminum to
enhance its strength and toughness [1–8].
Keeping in view the above facts, the present
work was planned to develop such material at
MUET labs, Jamshoro, Pakistan. For this
JoMME (2014) 16-20 © STM Journals 2014. All Rights Reserved
Fig. 1: Melting of Charge.
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A Study of Improvement
Hafiz Abdul Ahad Qazi
Tensile strength and percentage elongation of
all the samples was determined using Zwick/
Roell tensile test machine in the Department of
IT, MUET, Jamshoro, Pakistan as shown in
Figure 4.
The Vickers hardness test was conducted at
the Department of Metallurgy & Materials
Engineering, MUET, Jamshoro, Pakistan using
Vickers hardness testing machine. The details
of the mechanical properties such as tensile
strength, hardness and elongation are given in
Table 1.
Fig. 2: Molds, Pouring and Casted Sample.
EXPERIMENTAL WORK
Pure aluminum rods, zinc, magnesium and
copper were purchased from local market for
developing Al-Zn alloys. The aluminum rods
were melted in a graphite crucible and alloyed
with varying quantity of Zn with constant
amount of magnesium and copper metals. The
composition and manufacturing processing
details of the theoretically selected alloys are
given in Table 1 and Figures 1–3.
Once the aluminum came into complete
molten form at a temperature of 700 °C,
calculated amount of alloying elements i.e.,
zinc and magnesium were added and mixed
properly by a stirrer. Suitable amount of flux
and degasser were added at the end. After all
the above steps finally the molten charge was
casted in metal molds having dimensions-160
mm length, 12 mm width and 10 mm height.
The casting temperature was maintained at
700–730 °C.
Fig. 3: Rolling Machine.
The cast samples were hot rolled up to 4 mm
thickness at 350 °C to increase the strength of
casting alloy and decrease the casting defects
(as shown in Figure 3).
The rolled samples were machined to prepare
standard flat specimen for tensile test.
Prepared sample solution was heat treated at
500 °C in a muffle furnace for 1 hour and then
water was quenched at room temperature.
Fig. 4: Tensile Test Machine.
JoMME (2014) 16-20 © STM Journals 2014. All Rights Reserved
Page 17
Journal of Materials and Metallurgical Engineering
Volume 4, Issue 2
ISSN: 2231-3818 (online), ISSN: 2321-4236 (print)
RESULTS AND DISCUSSION
The strength of aluminum alloys depends upon
chemical composition and processing method.
Fig. 5: Stress–Strain Diagram of Pure Sample.
Considering the stress–strain diagram of the
sample (Figure 5), in received condition
without the addition of alloying elements, the
sample shows lower tensile strength equal to
145 MPa and percentage elongation of only
5.8. The tensile test result of alloy 1 (Figure 6)
showed an increase in tensile strength up to
Fig. 7: Stress–Strain Diagram of Alloy 2.
The main processing parameter
precipitation heat treatment.
is
the
Fig. 6: Stress–Strain Diagram of Alloy 1.
171 MPa and ductility up to 13%. This
increase in strength and ductility was due to
addition of 2% Zn and 2% Mg as alloying
elements in this alloy. This has been reported
in the literature that both the alloying element
increases the strength and ductility.
Fig. 8: Stress–Strain Diagram of Alloy 3.
JoMME (2014) 16-20 © STM Journals 2014. All Rights Reserved
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A Study of Improvement
Hafiz Abdul Ahad Qazi
Alloy 2 showed further increase in strength up
to 218 MPa and elongation up to 13 %
resulting in good strength and ductility. This
proves that both the properties of strength and
elongation increases with increase in
percentage of Zn (Figure 7).
The stress–strain diagram of alloy 3 containing
7% Zn, 8% Mg and 8% Cu showed the tensile
strength of 210.5 MPa and elongation up to
10.4% (Figure 8).
This decrease in strength may be due to
addition of Zn above 5%. It has been
mentioned in the literature that addition of Zn
above 5% will decrease the strength of alloy.
Whereas addition of Cu up to 2% could
increase the strength but it may decrease the
elongation which is practically true in the
present investigation [9–15].
By comparing the tensile test results of
original sample with sample 1, 2, and 3, it was
observed that the original sample showed
lowest strength and ductility as compared to
sample 1, 2, and 3.
Highest tensile strength and hardness were
observed in alloy 2 as compared to all other
samples resulting best properties.
Horizontal scale in Figure 9 shows numbering
of samples. Id number 1 represents pure
aluminum sample, Id number 2 represents
alloy 1, Id number 3 represents alloy 2 and Id
number 4 represents alloy 3. Vertical scale on
the left shows hardness in VHN and the same
scale show strain in percentage. The vertical
scale on the right shows strength in N/mm2 or
MPa.
From this combined graph it is found that as
strength of samples is increasing the hardness
is also increasing as can be seen how blue line
follows red line.
Table 1: Composition and Mechanical Properties of All Samples.
Sample No
Elements
Weight in grams
Percentage
Tensile Strength N/mm2
Strain % in inch
VHN (Mean)
Original
Alloy 1
Al
Al
Zn
400
400
10
100
95.7
2.4
144.83
5.79
5.8
171
13
9.46
Mg
Al
Zn
Mg
Al
Zn
Mg
Cu
8
400
20
8
400
30
8
8
1.9
93.45
4.67
1.9
89.68
6.73
1.79
1.79
218
12.6
15.836
210.46
10.42
13.2
Alloy 2
Alloy 3
Fig. 9: Combined Graphical Representation of Hardness, Strain and Strength.
JoMME (2014) 16-20 © STM Journals 2014. All Rights Reserved
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Journal of Materials and Metallurgical Engineering
Volume 4, Issue 2
ISSN: 2231-3818 (online), ISSN: 2321-4236 (print)
CONCLUSION






Addition of Zn and Mg increases the
strength and ductility after casting and
rolling of the samples.
Highest strength up to 218 MPa was
achieved in alloy 2 containing 5% Zn and
2% Mg.
Highest ductility (percentage elongation)
up to 13% was also obtained in alloy 2.
Percentage of Zn above 5% decreases the
tensile strength and ductility even does not
increase with addition of 1.7% Cu in the
alloy. The hardness of Al alloy depends
upon percentage of alloying elements.
Lowest mechanical properties including
the strength and hardness were recorded in
pure aluminum.
The overall properties of aluminum alloy
showed good relation with composition
and heat treatment which increases the
strength.
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