Solution Treatment AC8A Aluminum with Aging Temperature
Variations on Density, Hardness and Microstructure
Roymons Jimmy Dimu, Antonius Pangalinan, Oktovianus Dharma Rerung, Mamiek Mardyaningsih
and Yanes Boimau
Mechanical Engineering Department, State Polytechnic of Kupang, Street Adisucipto, Kupang City, Indonesia
Keywords: Aluminum AC8A, Temperature aging, Density, Microstructure and Hardness.
Abstract: Solution Treatment is the process of heating the material and cooling it with a fast cooling rate. The solution
treatment process with rapid cooling can cause dislocations, so it is necessary to carry out the aging process.
This study aims to smooth the coarse primary silicon structure and eliminate dislocations on the surface of
the piston material and also to determine the hardness of the material and the density of the material through
solution treatment with variations in aging temperature. The method used in this study is a direct experiment
with AC8A aluminum solution treatment at a temperature of 490
0
C for 1 hour then quenched with water
cooling media. The material resulting from the solution treatment was observed for microstructure, density
and hardness. Then the material is subjected to an aging process with variations in aging temperatures of 125
0
C, 150
0
C and 175
0
C holding time for the same 30 minutes. After completion, observations of microstructure,
density, and hardness tests were carried out for each treatment. The results of the study of homogeneous
microstructure with the smallest crystal grain size occurred in the aging process with a temperature of 150
0
C.
Density value or the highest density occurs in the aging process with a temperature of 150
0
C. The highest
hardness value occurs in the aging process with a temperature of 175
0
C.
1 INTRODUCTION
Aluminum alloy is a material that is widely used in
industry and automotive, AC8A aluminum material is
one of the aluminum alloys used for automotive
components, one of which is the piston. The piston is
the main component in an engine that moves up and
down in the cylinder doing the intake, compression,
effort, exhaust. The main function of the piston is to
receive combustion pressure and transmit combustion
pressure through the piston rod to the crankshaft.
Pistons receive high temperatures and pressures, so a
material that has good durability is needed. AC8A
aluminum is aluminum silicon alloy which has Si
content between 11-13% wt. The high silicon content
in AC8A aluminum or piston material acts as an
insulator to prevent aluminum from absorbing
excessive heat and silicon can increase the hardness
and wear-resistant properties of the piston. The
weakness of pistons with high silicon content is brittle
or brittle as the silicon content increases so that the
morphology of the primary silicon is coarse and large.
(Indriyati, 2008). For this reason, it is necessary to have
Solution Treatment to get a solid solution that is close
to homogeneous. Refining the silicon crystal structure
to remove or eliminate the coarse and large primary
silicon crystal structure this structure can cause brittle
properties. Solution Treatment is a process of heating
the material and cooling it with a fast cooling rate
(Wibowo & Nurato, 2018). The solution treatment
process with rapid cooling can cause dislocation, so an
aging process is necessary (Dimu, 2020).
In this research, the piston material that has been
treated with solution treatment with water cooling
media will be subjected to an aging process with
variations in aging temperature. By varying the aging
temperature, it is expected that maximum hardness
and a homogeneous structure without dislocation can
be obtained. And also in this study, we want to know
the density of the material after solution treatment and
after the aging process.
2 LITERATURE REVIEW
This study aims to smooth the coarse primary silicon
structure and eliminate dislocations on the surface of
the piston material and also to determine the hardness
Dimu, R., Pangalinan, A., Rerung, O., Mardyaningsih, M. and Boimau, Y.
Solution Treatment AC8A Aluminum with Aging Temperature Variations on Density, Hardness and Microstructure.
DOI: 10.5220/0010944600003260
In Proceedings of the 4th International Conference on Applied Science and Technology on Engineering Science (iCAST-ES 2021), pages 309-313
ISBN: 978-989-758-615-6; ISSN: 2975-8246
Copyright
c
 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)
309

of the material and the density of the material through
solution treatment with variations in aging
temperature.
There are several previous studies that serve as the
first reference, namely the analysis of the effect of
temperature instability on the results of the material
hardness of the piston heat treatment process resulting
in the hardness of the material obtained depending on
the aging temperature setting, the lower the
temperature, the higher the hardness, while the higher
the temperature the hardness will decrease (Wibowo &
Nurato, 2018). The solution treatment process with
rapid cooling can cause dislocation, so an aging
process needs to be done (Dimu, 2020). The solution
treatment temperature is 490
o
C and the temperature of
the fluid itself must be in the range of 60
o
C, this is
because to prevent the material from cracking /
breaking during immersion due to significant
temperature differences (Wibowo & Nurato, 2018). the
effect of artificial aging time on the crystal structure of
dislocation density and hardness in the Al-7075 alloy
resulted in Aluminum 7075 reaching its maximum
hardness at an artificial aging temperature of 200
o
C
with a holding time of 1 hour of 23,035 HBN and the
smallest crystal size occurred in artificial aging heat
treatment at a temperature of 200
o
C holding time 24
hours at 3.4405 nm (Dian Permata Putri*, Budiarto
Jono Siswanto, 2020). Testing the crystal size of the
micro-lattice strain dislocation density with XRD on
the effect of artificial aging temperature on Al 5052
alloy shows that the crystal size value is inversely
proportional to the artificial aging temperature where
the higher the artificial aging temperature the smaller
the crystal size, while for the dislocation density and
density the lattice is proportional to the temperature so
that along with the high temperature, the value of
dislocation density and lattice density also increases
(Regi Megantara, Budiarto Djono Siswanto*, 2020).
The effect of solution treatment and artificial aging on
the mechanical properties and microstructure of A383
aluminum alloy. From the optimization results, the best
hardness is with aging temperature of 200
o
C and
holding time of 88 minutes or aging temperature of
100
o
C with holding time of 30 minutes. (Sultan &
Hamzah, 2019).
Furthermore, in the study of the microstructure
and mechanical properties of al-si alloys under heat
treatment conditions, the results of microstructural
observations show that the eutectic silicon particles
are spherical and homogeneously distributed in grain
boundaries after T6 heat treatment. (Moh. Indra P,
Mahros Darsin, 2011).
Figure 1: Research roadmap.
3 METHOD
The steps in this research:
1. Making specimens taken from pistons on the
market
2. Prepare all tools and materials.
3. Put the specimen into the furnace and carry out
the solution treatment process with a heating
temperature of 490
0
c.
4. After heating the specimen to 490
0
c, do the
holding time for 1 hour.
5. Remove the specimen from the furnace quickly,
do quenching with water media (cooling media
temperature 60
0
c ± 2).
6. Testing density, hardness and hardness
materials from solution treatment.
7. Put the specimen into the furnace and carry out
the aging process at a heating temperature of
125
0
c with a holding time of 30 minutes.
8. Repeat step 7 for aging temperatures of 150
0
c
and 175
0
c with the same holding time of 30
minutes.
9. Observing the microstructure using an optical
microscope, hardness and density.
Density is a physical quantity that is the ratio of
mass (m) to the volume of the object (v). The
measurement of the density of the material in the form
of solids or bulk used the Archimedes method. To
calculate the actual and theoretical density values
used Equation:
Actual density:
……..(Fahmi Fasya, 2015)
With:
ρm : Actual density (gr/cm
3
)
ms :
Dry sample mass (gr
mg :
mass of sample suspended in water (gr)
ρ H2O : density of water = 1 gr/cm
3
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4 RESULT AND DISCUSION
4.1 Test Result
4.1.1 Hardness Test Result Data
Table 1: Material Solution Treatment 490
0
C holding time
1 hour.
No Treatment
Hardness Value
(HRB)
1
Solution Treatment 490
0
C
holding time 1 hour
67,29
2 69,74
3 69,95
Average Hardness Value (HRB) 68,99
Table 2: Treatment material Solution Treatment 490
0
C
followed by the Aging process at a temperature of 125
0
C.
No Treatment
Hardness Value
(HRB)
1
Aging 125
0
C
75,26
2 76,51
3 77,12
Average Hardness Value (HRB) 76,29
Table 3: Material treatment Solution Treatment 490
0
C
followed by Aging process at a temperature of 150
0
C.
No Treatment
Hardness Value
(HRB)
1
Aging 150
0
C
79,55
2 79,66
3 78,05
Average Hardness Value (HRB) 79,08
Table 4: Material treatment Solution Treatment 490
0
C
followed by Aging process at a temperature of 175
0
C.
No Treatment
Hardness Value
(HRB)
1
Aging 175
0
C
84,74
2 85,49
3 84,69
Average Hardness Value (HRB) 84,97
Figure 2: Graph of the relationship between material
treatment and the average hardness value.
4.1.2 Density Test Data
Density testing is carried out based on Archimedes'
law. Density testing is carried out to find the value of
porosity in the specimen. The equipment used is the
One Mad brand scale with an accuracy of 0.01 grams
and water fluid. The results of the density test can be
seen from Table 5.
Table 5: Density Test Data.
NO Treatment
Dry mass
of the test
specimen
(gr)
Mass of the test
specimen was
hung in water
(gr)
Actual
density
(gr/cm
3
)
1
Solution
Treatment
490
0
C
1,81 0,66 1,57
2
Aging
125
0
C
1,82 0,67 1,57
3
Aging
150
0
C
2,51 0,98 1,64
4
Aging
175
0
C
2,88 1,11 1,62
0
10
20
30
40
50
60
70
80
90
Solution
treatmen
490 0C
Aging 125
0C
Aging 150
0C
Aging 175
0C
Hardness (HRB)
Solution Treatment AC8A Aluminum with Aging Temperature Variations on Density, Hardness and Microstructure
311

4.1.3 Microstructure Observation Data
Figure 3: The microstructure of the material resulting from
the solution treatment process at a temperature of 490
0
C.
Figure 4: The microstructure of the material resulting from
the solution treatment process at a temperature of 490
0
C
and continued with the Aging process at 125
0
C.
Figure 5: The microstructure of the material resulting from
the solution treatment process at a temperature of 490
0
C
and continued with the Aging process at 150
0
C.
Figure 6: The microstructure of the material resulting from
the solution treatment process at a temperature of 490
0
C
and continued with the Aging process at 175
0
C.
4.2 Discussion
4.2.1 Analysis of Hardness Test
From the results of hardness testing, it can be seen
that the average hardness value of the solution
treatment material with a temperature of 490
0
C
holding time 1 hour is 68.99 HRB. In the Aging
process with a temperature of 125
0
C the material
experienced an increase in the hardness value to 76.29
HRB. and also for the aging process with a
temperature of 150
0
C an increase in the hardness
value of 79.08 HRB. The hardness value continues to
increase to 84.97 HRB for the aging process with a
temperature of 175
0
C. It can be seen that the material
resulting from solution treatment which continues
with the aging process, the hardness value continues
to increase in direct proportion to the increase in
aging temperature.
4.2.2 Density Test Analysis
From the results of the density test, it can be seen that
the density value in the solution treatment treatment
of 490
0
C is 1.57 gr / cm
3
and in the aging process at
125
0
C the density value does not change, namely
1.57 gr / cm
3
. In the aging process at 150
0
C the
density value increases to 1.64 gr /cm
3
. The density
value decreased to 1.62 gr/cm
3
in the aging process
with a temperature of 175
0
C. The highest density
value or density occurs in the aging process of 150
0
C, if it is seen from the observation data of the
microstructure of the smallest or smoothest crystal
size, it is also in the aging process of 150
0
C.
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4.2.3 Analysis of Microstructure
Observations
From the observation of the microstructure, it can be
seen that the material resulting from the 490
0
C
solution treatment occurred dislocation due to the
rapid cooling process. In the aging process at 125
0
C,
it is still visible at the location and in the aging
process at 150
0
C, a fine and fairly homogeneous
microstructure is formed. Starts to form primary
silicon structure deposits in the aging process with a
temperature of 175
0
C.
5 CONCLUSION
Based on the results of this study, several conclusions
can be drawn as follows:
1. Homogeneous microstructure with the smallest
crystal grain size occurs in the aging process
with a temperature of 150
0
C.
2. Density value or the highest density occurs in
the aging process with a temperature of 150
0
C.
3. The highest hardness value occurs in the aging
process with a temperature of 175
0
C.
ACKNOWLEDGEMENTS
Thank you to the politeknik negeri kupang because
this research can fund the scope of routine lecturers'
research through the DIPA PNK 2021 funding
source.
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