Materials Sciences and Applications, 2010, 1, 199-201
doi:10.4236/msa.2010.14031 Published Online October 2010 (http://www.SciRP.org/journal/msa)
199
Effect of Heat Treatment on Mechanical
Properties of Al-1.5Cu-9.5Zn-3Mg Rapidly
Solidified Alloy
El Said Gouda1,2, Emad Makboul Ahmed1, Nabih Lotfi Tawfik1
1Metal Physics Lab., Solid State Physics Department, National Research Center, Dokki, Egypt; 2Physics Department, Faculty of
Science, Jazan University, Jazan, K.S.A.
Received April 29th, 2010; revised June 17th, 2010; accepted June 18th, 2010.
ABSTRACT
Ribbons with the composition Al-1.5Cu-9.5Zn-3Mg were prepared by melt spinning technique. Microhardness and ten-
sile strength were measured. The melt spun hardness and ultimate tensile strength values were as high as 291 HV and
660 MN/m2, respectively. Hardness values are relaxed to lower values on prolonged thermal annealing to around 50%.
X-ray diffraction lines corresponding to Cu, Zn and Mg were disappeared for the as melt spun ribbons, which indicates
a complete solubility of these element in Al matrix. On prolonged thermal annealing these alloying elements were pre-
cipitated.
Keywords: Microhardness, Rapid Solidification, UTS, Tensile Strength
1. Introduction
The study of the material strength is an important subject
because it is the first characteristic comes in mind when
used in industrial applications specially that subjected to
shock loading. Steel is a good example for the most
strength materials, but its high density restricts its uses.
Aluminum alloys are increasingly employed in many
important manufacturing areas, such as the automobile
industry, aeronautics and the military [1]. Currently, it
offers the greatest potential for cost effective weight
savings in automotive body structures and closures. With
a density of only 33% of that of steel and a greater
strength to weight ratio, there is the possibility for a
weight savings of 40% to 50%. Also, Mg alloys are very
attractive materials for producing lightweight compo-
nents for automobiles because they have densities that
are 66% of Al alloys and 22% of steel. With their lower
density and moderate strength, Al-Mg alloys are well
suited for a number of applications, ranging from steering
wheels and instrument panels to engine and transmission
components. The mechanical properties of the Al-Mg plas-
tically processed alloys depend on the content of magne-
sium in the alloy. With an increase of magnesium from
0.5 to 5% the properties increase; this rise is greater
when magnesium increases from 3 to 6% [2]. There are
many studies characterize the strength and mechanical
properties of Al-based and Mg-based alloys with differ-
ent elements [3-8]. The present paper aims to character-
ize hardness and tensile strength of the quaternary alloy
Al-1.5Cu-9.5Zn-3Mg as an example for a high strength
material.
2. Experimental
Al-1.5Cu-9.5Zn-3Mg alloy was prepared from 99.75
wt.% pure Al, 99.9 wt.% pure Cu, Zn and Al-10 wt.%Mg
master alloy. The required quantities were weighted out
and melted in electrical resistance furnace then thermally
agitated to ensure the homogenization. The molten alloy
was casted into graphite moulds to produce rods of 25
mm length and 4 mm diameter. A stream of the molten
alloy at 850℃ was ejected by argon gas at a gauge pres-
sure of 1.5 atm., from a silica tube with 0.5 μm orifice
diameter. The melt jet fell on a copper wheel of the melt
spinning apparatus fixed at 2950 r/m. The estimated
cooling rate was about 105 K/s. The resulting alloys are
in ribbons form of about 50 μm thickness and width 2
mm. X-ray diffraction analyses was performed to iden-
tify the structure of the ribbons using a 1390 Philips
X-ray Diffractometer with Cu radiation. The ribbons

Effect of Heat Treatment on Mechanical Properties of Al-1.5Cu-9.5Zn-3Mg Rapidly Solidified Alloy 200
were tensile tested with a gauge length of 5 cm at strain
rate of 1.66 × 10-5 s-1, at room temperature. Measure-
ments of hardness were done with the specimen placed
against a glass slide with a load of 150 gm and indenta-
tion time of 10 s. Tests were done for the as melt-spun
ribbons and for fully aged ribbons.
3. Results and Discussion
3.1. X-Ray Diffraction
The cooling rates of the melt spinning process exceed 105
℃/s was high enough to retain the high concentrations of
the alloying elements in solid solution with the Al-
1.5Cu-9.5Zn-3Mg alloy. This was confirmed by the pre-
sence of Al reflections only in the X-ray diffraction pat-
tern of the as melt-spun ribbons as illustrated in Figure 1.
For aged ribbon, the Al-Cu compound and the alloying
elements start to precipitate and crystal growth starts to
be exist, so additional X-ray diffraction peaks were
formed for the aged ribbons as illustrated in Figure 2.
The additional diffraction lines were corresponding to
pure Mg, Zn and Al2Cu phases.
3.2. Tensile Test
Samples for the tensile test were chosen such that, a
minimum variation in width and thickness has been ob-
tained. The stander deviation in cross sectional area for
each sample is ±5%. Samples with gauge length 5 cm
were tested. Figure 3 shows the load-elongation curves
for as melt-spun and annealed ribbons. Each curve can be
divided into two regions. The first region is a linear and
ends at strain ratio ε/εf about 80% and 30%, for the as
melt-spun and annealed samples, respectively, εf is the
fracture strain. The second region is slightly curved due
to yielding near the end of the test. Slope of the straight
line in the first region represents Young’s modulus of the
as melt-spun sample. The ultimate tensile strength (UTS)
for the as melt-spun sample was 660 MN/m2. This value
decreased by annealing at 300℃ for 5 h to 442 MN/m2.
Also, toughness, which is expressed as the area under the
load-elongation curve until fracture, was calculated. It
was 3.98 MN/m2 for the as melt-spun samples and 3.39
MN/m2 for the annealed sample.
3.3. Microhardness
Hardness of the as melt spun Al-1.5Cu-9.5Zn-3Mg alloy
is 291 MN/m2 and decreases to 145 MN/m2 by thermal
ageing at 220℃ for 5 h. This decrease takes place in two
stages as illustrated in Figure 4. An initial fast stage fol-
lows by slow stage in which a slight decrease in hardness
can be observed. The as-cast rod with the same composi-
tion gives the value of 141 MN/m2. By comparing the
two values, it is noticed that, the as melt-spun ribbon
has a much higher value than that of the as cast rods,
which agreement with other results [9] for alloy rapidly
solidified at different cooling rates. On thermal aging, the
Figure 1. X-ray diffraction pattern of the Al-1.5Cu-9.5Zn-
3Mg melt spun ribbon.
Figure 2. X-ray diffraction pattern of the Al-1.5Cu-9.5Zn-
3Mg annealed ribbon.
(a) (b)
Figure 3. Load versus elongation for Al-1.5Cu-9.5Zn-3Mg
melt spun ribbons (a) as melt spun and (b) aged for 5 h at
300℃.

Effect of Heat Treatment on Mechanical Properties of Al-1.5Cu-9.5Zn-3Mg Rapidly Solidified Alloy 201
Figure 4. Variation of Vickers hardness ratio H (t)/H (0) at
170 and 220℃ with aging time.
hardness decreases to reach limiting values of 50% of the
as melt-spun values. It was observed that the hardness
relaxation during isothermal ageing is much slower than
that of resistivity relaxation at the same temperature. This
behavior can be explained as that, hardness is closely
related to size of precipitates. Also the electrical resistiv-
ity is sensitive to point defects which are usually the first
properties to recover. On the other hand, the hardness
depends more on line imperfection which may require
higher temperatures for recovery. So, rapid solidification
has a significant effect on increasing the hardness. The
higher value of hardness for the as melt spun state can be
attributed to the effect of the solute atoms upon the sol-
vent lattice and the nature of the lattice forces operative
owning to the interaction of different atomic spices.
4. Conclusions
The effects of rapid solidification and thermal heat treat-
ments on the mechanical properties of quaternary Al-
1.5Cu-9.5Zn-3Mg melt spun alloy were studied. A maxi-
mum solid solubility value of 9.5 wt.% Zn in α-Al was
obtained for the as melt-spun alloy, 3% Mg and 1.5% Cu
were also obtained as solid solutions in Al-matrix. The
existence of the alloying elements as solid solution in
α-Al significantly enhances microhardness, ultimate ten-
sile strength U.T.S values. After aging the values relaxed
to lower values as a result of the Al2Cu, Zn and Mg pre-
cipitations. Hardness and U.T.S were as high as 291 HV
and 660 MN/m2, respectively.
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