Mechanical Properties and Microstructure Aspects of AlSi10Mg [600305]

Mechanical Properties and Microstructure Aspects of AlSi10Mg
Casting in Vibrating Field
TIEREAN Mircea Horia1,a, BALTES Liana Sanda1,b* and
BANEA Alexandru Stefan1,c
1Transilvania University of Brasov, 29 Eroilor Blvd., 500036 Brasov, Romania
amtierean @unitbv.ro , [anonimizat] , [anonimizat]
Keywords: AlSi10Mg alloy, casting, vibration, silicon phase .
Abstract. Aluminum alloys are one of the most extended groups of functional materials by reason
of combination between good mechanical pr operties and low mass. The aim of the present paper is
to test the influence of the vibrations on the AlSi10Mg (EN 1706 -2010) solidification. For
comparison, six lots were casted in cold and preheating molds, with or without vibrations within 50
Hz and 105 0 Hz. For each casting frequency was measured the silicon phase dimension, hardness,
tensile stress and impact strength. The mechanical properties increase with the vibration frequency.
Increasing the vibration frequency, the structure will be refined and also the size of the silicon
phase is decreasing. Considering that one source of porosity is the gas entrapped or dissolved in the
liquid metal during the casting, using vibration along casting and cooling allows it’s decreasing.
Introduction
Commercial ca st aluminum alloys are polyphase materials that strongly influence the high
specific tensile strength compared with other cast alloys, such as ductile cast iron or cast steel
[1,2,3]. Vibration during solidification has a significant contribution to increasi ng of mechanical
properties [ 4,5].
Labisz et al. investigated the effect of cooling rate on the size and distribution of the
precipitation occurred in AC -AlSi7Cu3Mg aluminum cast alloy [6]. The solidification process was
done without any protective atmosph ere in the open air, the cooling rates being between 0.2 șC/s and
1.25șC/s. The SEM micrographs revealed a dendritic silicon phase having approx. 100 μm length
and 10 μm thickness.
In [7] Sun et al. analyzed the nucleation and growth of eutectic cell in hypoeutectic Al−Si alloy.
The tested material was Al−10%Si alloy modified by 0 .025% Sr. Authors found that irregular
eutectic Si and branches had no rational or consistent growth axes. The SEM micrographs revealed
the approx. 15 μm length and 3 μm thickness of dendritic silicon.
Al Helal et al. investigated the refinement a nd modification of silicon phases in hypereutectic
Al-Si alloys. The tested material was Al -18Si [8]. The untreated Al -18Si contains coarse primary
silicon phase with average particle size of approximately 50 µm and the silicon eutectic had a
mostly plate -like morphology. The conventionally cast Al -18Si treated with P and Sr contains
refined primary Si particles with average particle size of 20 µm dispersed in a partially modified
Al-Si eutectic matrix. In Al -18Si treated with P and Sr using the solid -liquid duplex casting system
the primary Si was refined to less than 15 μm and the eutectic Si has a fibrous structure.
In [9] Singh et al. characterize the primary Si particles from permanent mold -cast unmodified
Al-12 wt.% Si -1 wt.% Ni base co mmercial alloy. The 3D topology and first -order geometric
attributes (volume, surface area and mean diameter) of the primary Si particles measured directly
from their 3 -D digital images were reported. The 3D volume of materials was reconstructed fr om
80 montage serial sections, each of them having a pixel resolution of 0.3 µm. The obtained volume
of primary Si particles was 1.45·106 µm3.

Abu-Dheir et al [10] demonstrated that through solidification of Al – 12.5 % Si aluminum alloy
in vibrating condi tions, the increasing of vibrations’ amplitude reduces the interlamellar distance
and changes the morphology of Si, which becomes more fibrous. Vibrating solidification caused an
increase in elongation of 19 … 68%, accompanied by increasing of the tensil e stress .
Chirita et al. analyzed the influence of the vibrations on the solidification of AlSi18 alloy [11].
The excitation was performed horizontally with an amplitude of 0.5 mm and three frequencies of 0,
8 and 24 Hz. F or 8 Hz frequency was obtained 31% increasing of the tensile strength compared
with static solidification. The same trend was observed in the study of the thickness of the Si
lamellas. In the case of solidification with vibration at 8Hz, a decrease in the thickness of the Si
slides is o bserved. At low frequency and excitation in the vertical direction, with spheroidizing
annealing, Gencalp et al [12] discovered an increasing of silicon phase.
Wang et al. demonstrated the presence of primary Si in cast hypoeutectic Al−Si alloys
investigating their growth [13]. The tested material was Al−10%Si alloy melted at 715 șC, kept for 2
minutes and then cooled with different cooling rates, between 3.8 șC/s and 16.1 șC/s. Lots of primary
Si particles that occu r in the hypoeutectic Al−Si alloy were found. Increasing the cooling rate from
3.8șC/s to 16.1 șC/s, the equivalent diameter of primary Si particles was reduced from 88.9 μm to
17.1 μm. The dimension of α(Al) decreases with increasing the cooling rate. The paper presents
also the nucleation and growth mechanisms of primary Si particles. The authors presume that,
during solidification, Al atoms are rejected by Si diffuses through the liquid toward the liquid/α(Al)
interface, and they are incorporated into the α(Al) phase. Similarly, Si atoms are rejected by Al
diffuse toward the liquid/Si interface, and they form a cluster of Si atoms in the liquid. The
concentration of Si clusters increases with solidification time and once it exceeds eutectic
concentration, the primary Si particles are shaped from the liquid.
Barbosa and Puga studied the Al7Si0.3Mg alloy [ 14]. High frequency vibrations (20 kHz) were
applied at 1000W electric power. It was observed approx. 20% increasing of the ultimate tensile
strength, 50% o f the yield strength and 15% of the elongation .
The effects of ultrasonic vibrations on die casting of AA7075 alloy have been investigated by
Haghayeghi et al. [15]. There were applied vibration frequencies of 10, 14, 17.5 and 20 kHz with a
power of 4kW. The tests reveal the reduction of the grain size up to 73% and up to 5% of the
porosity. The obtained ultimate stress was 590 MPa, the yield stress was 502 MPa and elongation
improved to 18%.
The microstructure and mechanical properties of 7039 alloy were t ested by Mishra and Sharma
after casting with microwaves at 2.45 GHz and 1400 W [16]. The yield strength increased with
22%, the ultimate tensile strength increased with 33%, the elongation increased with 20%, while the
medium reduction of the grain size w as approx. 28%.
The goal of the present paper is to test the influence of the vibrations on the AlSi10Mg (EN
1706 -2010) solidification.
Sample preparation and operating methods
For the samples preparation, AlSi10Mg alloy were used, with the chemical compos ition
according to the EN AC -AlSi10Mg (EN 1706 -2010). The cylindrical shape dimensions of the
samples were ϕ20×150 mm, obtained by different casting conditions.
The metal mold material was carbon steel S 235 (SR EN 10025 -2:2004). The mold was designed
in two mold parts with one vertical separation plane . The mold was cold or preheated.
The AlSi10Mg alloy, with the chemical composition before mentioned, was melted in an open
flame furnace at 720 șC, ma intaining and casting in four cavity mold, with vibrations, th e frequency
range between 0 Hz to 1050 Hz (Table 1).
For metallographic inspection , the bottom part of 12 mm length was removed from the casted
samples (from A to F, Table 1) . The samples having Φ20x10mm dimensions w ere prepared for
metallographic and hardness research, in each of the studied cases. The samples were polished and
5% fluorohydrin acid reagent was used.

Table 1. Samples and conditions
Samples symbol Mould temperature Frequency [Hz]
A cold 0
B preheating 0
C preheating 50
D preheating 350
E preheating 675
F preheating 1050

The experimental assembly casting/vibration specially designed for this research are detailed
presented in [ 17,18 ]. The infrared thermometer Omegascope OS523E for temperature
measurements was used; the range of tem perature is between 0 and 1370°C. Mold temperature
analysis along with the tests was performed using the Thermovision camera FLIR ThermaCAM
S45, the temperature range being from -40 to +1500°C. Scanning electron microscope (SEM
3500N, Hitachi) was used, wi th energy dispersive X -ray device (EDX Thermo Scientific Ultra
Dry). Each solidified sample was SEM and EDS tested. The magnifications were 140x … 500x.
Results
The values of densities and hardness of the samples prepared according to conditions presented
in the precedent paragrap h are presented in Fig. 1 and Fig. 2.

Fig. 1. The influence of frequency on the density
of AlSi10 Mg Fig. 2. The influence of frequency on the
hardness of AlSi10 Mg

The values of ultimate tensile stress and yield s tress are presented in Fig. 3. The values of
elongation are presented in and Fig. 4.

Fig. 3. The influence of frequency on the
ultimate tensile stress and yield of AlSi10 Mg Fig. 4. The influence of frequency on the
elongation of AlSi10 Mg

SEM microstr uctures (500x) are presented in figures 5, 6, 7, 8, 9 and 10, for determination of the
silicon phase dimension.

Fig. 5. Sample cast in cold mold (A), without
vibration s Fig. 6. Sample cast in preheated mold (B),
without vibrations

Fig. 7. Cast sample preheated (C), vibrations
50Hz Fig. 8. Cast sample preheated (D), vibrations
350Hz

Fig. 9. Cast sample preheated (E), vibrations
675Hz Fig. 10. Cast sample preheated (F), vibrations
1050Hz

The next figures (Fig. 11 … Fig. 14 ) show the results of the EDS tests .

Element
Line Net
Counts Weight % Atom %
Al K 98838 70.03 70.87
Si K 21647 29.97 29.13
Total 100.00 100.00

Element
Line Net
Counts Weight % Atom %
Al K 143577 69.91 71.93
Si K 28588 26.69 26.38
Fe K 1012 3.39 1.69
Total 100.00 100.00

Fig. 11. SEM and EDS for sample C (table 1) Fig. 12. SEM and EDS for sample D (table 1)

Element
Line Net
Counts Weight % Atom %
Al K 164139 70.29 71.12
Si K 35453 29.71 28.88
Total 100.00 100.00

Element
Line Net
Counts Weight % Atom %
Al K 206877 72.20 72.99
Si K 40131 27.80 27.01
Total 100.00 100.00

Fig. 13. SEM and EDS for sample E (table 1) Fig. 14. SEM and EDS for sample F (table 1)

Related subjects were researched by Dinnis C.M. et al. [19], Dobkowska A. [20] and Tillová E.
[21]. Tillová et al. reveal the three -dimensional morphology of the silicon particles and also the
intermetallic phases, usefully results helping our research. The tests data obtained by Dobkowska et
al. were for AlSi10Mg sand casting alloy and offered the possibility to compa re these two types of
casting.
Discussion
From the Fig. 1 to Fig. 4. it can be observed the increasing of density, hardness, tensile stress and
elongation with vibration frequency. As was demonstrated in [ 17], the vibrations break down the
dendrites , resul ting spherical shape solid solution domains .
The vibrations also reduce the porosities inside material. The main types of internal porosity are
shrinkage and gas pores. Pores can affect the results of surface treatment. Gas pores usually look
like a round holes. Porosity reduction involves an increase of compactness of the cast material,
which can be covered by vibrated casting. This is proved if we compare for example the
microstructure from Fig. 1 1, which was casted with low frequency vibra tion and those from figure
14, where the frequency was 1050 Hz.
Analyzing microstructures from Fig. 5 to Fig. 10 one may see that as vibration frequency
increases, the size of the silicon phase decreases. Variation of the Si phase size is presented in Fig.
13. The silicon growth mechan ism in the structure was demonstrated by Wang et al. [13] .

Fig. 1 5. The influence of frequency on the Si phase dimension

The size of the silicon phase is not the only one influenced. The results of EDS for the
hypoeutectic A l-Si alloy revealed the increas ing of the net cou nts with increas ing of frequency (Fig.
11…Fig. 14) .
Aluminum reacts also very quickly with atmospheric oxygen and forms the oxide film. Also,
iron can enrich particles and give rise to gas pores and shrinkage effect.
Conclusions
Al-Si alloys , due to the silicon properties to increase their mechanical propertie s, are interesting
for aerospace, aut omotive and electrical industries, but not only. Aluminum -silicon alloys are also
highly versatile materials. For industrial applications, the majority of these alloys are hypoeutectic
alloys. The performances of these alloys depend on the adjustm ent of the cast microstructure, which
means microstructural characteristics and level of defects. The hypereutectic alloys are more wear –
resistant but less ductile than hypoeutectic alloys [2 4].
This research demonstrates the positive influence of the vi bration during solidification on the
mechanical properties of AlSi10Mg alloy. Since porosity is the main defect in cast aluminum

alloys, it is indicate d a possibility to reduce the size of the silicon phase and obtain a microstructure
in which the casti ng defects as shrinkage and gas pores can be reduced . Considering that one source
of porosity is the gas entrapped or dissolved in the liquid metal during the casting, using vibration
along casting and cooling allows their decreasing. A finer structure was also observed and as
mentioned in the discussion, the size of the silicon phase is also decreasing.
References
[1] M. Warmuzek, Aluminum -Silicon Casting Alloys. An Atlas of Microfractographs, ASM
International (2004).
[2] G.L. Pintilei , V.I. Cri smaru, M. Abrudeanu, C. Munteanu, D. Luca, B. Istrate, The influence of
ZrO2/20%Y2O3 and Al2O3 deposited coatings to the behavior of an aluminum alloy subjected
to mechanical shock . Applied Surface Science 352 (2015) 169–177.
[3] M.Nicoara, A.Raduta, C.Locovei, Computer -aided evaluation of particle distribution in
metallic matrix composites, Proceedings of the Euro International. Powder Metallurgy
Congress and Exhibition, Euro PM 2011, 110 –117.
[4] F. Taghavi, H. Saghafian, Y.H.K. Kharraz i, Study on the ability of mechanical vibration for the
production of thixotropic microstructure in A356 aluminum alloy. Materials and Design 30
(2009) 115 –121.
[5] M.A. Luca, T. Pisu Machedon, Vibration influence on polycrystalline structure and internal
friction of th e material deposited by welding . Journal of Optoelectronics and Advanced
Materials 7-8 (2013 ) 655 –661.
[6] K. Labisz, M. Krupiński, L.A. Dobrzański, Phases morphology and distribution of the Al -Si-Cu
alloy. Journal of Achievements in Materials and M anufacturing Engineering, volume 37, issue
2, December 2009, 309 –316.
[7] Y. Sun, S.P. Pang, X.R. Liu, Z.R. Yang, G.X. Sun, Nucleation and growth of eutectic cell in
hypoeutectic Al−Si alloy. Transaction of Nonferrous Metals Society of China Series, Elsevier
21 (2011) 2186 –2191.
[8] K. Al -Helal, I.C. Stone, Z. Fan, Simultaneous prim ary Si refinement and eutectic modification
in hypereutectic Al-Si alloys . Transactions of the Indian Institute of Metals, December 2012,
Volume 65, Issue 6, 663 –667.
[9] H. Singh, A.M. Gokhale, A. Tewari, S. Zhang, Y. Mao, Three -dimensional visualization and
quantitative characterization of primary silicon particles in an Al –Si base alloy. Scripta
Materialia 61 (2009) 441 –444.
[10] N. Abu -Dheir, M. Khraisheh, K. Saito, A. Male, Silicon morphology modification in the
eutectic Al -Si alloy using mechanical mould vibra tion. Materials Science and Engineering A
393 (2005) 109 –117.
[11] G. Chirita, I. Stefanescu, D. Soares, F.S. Silva, Influence of vibration on the solidification
behaviour and tensile properties of an Al –18wt%Si alloy. Materials and Design 30(5) (2009)
1575 -1580.
[12] S. Gencalp, N. Saklakoglu, Effects of low -frequency mechanical vibration and casting
temperatures on microstructure of semisolid AlSi8Cu3Fe Alloy. Arabian Journal for Science
and Engineering, December 2012, Volume 37, Issue 8, 2255 –2267.
[13] S.R. Wang, R. Ma, Y -Z. Wang, Y. Wang, L. Yang, Growth mechanism of primary silicon in
cast hypoeutectic Al−Si alloys. Transaction of Nonferrous Metals Society of China Series,
Elsevier 22 (2012) 1264 –1269.

[14] J. Barbosa, H. Puga, Ultrasonic melt processing in the low press ure investment casting of Al
alloys. Journal of Materials Processing Technology 244 (2017) 150 –156.
[15] R. Haghayeghi, A.Heydari, P.Kapranos, The effect of ultrasonic vibrations prior to high
pressure die -casting of AA7075, Materials Letters 153 (2015) 175 –178.
[16] R.R. Mishra, A.K., Structure -property correlation in Al –Zn–Mg alloy cast developed through
in-situ microwave casting, Materials Science & Engineering A 688 (2017) 532 –544.
[17] M.H. Tierean, L.S. Baltes, A. Banea, Influence of the vibrations on AlSi10Mg casti ng alloy
structure. Advanced Materials Research 1114 (2015) 166 -171.
[18] M.H. Tierean, L.S. Baltes, M. Luca, A. Banea, Measurements of dynamic Young modulus of
AlSi10Mg alloy cast in vibrating field. Journal of Optoelectronics and Advanced Materials 11 –
12 (20 15) 1868 -1873.
[19] C.M. Dinnis, A. K. Dahle, J. A. Taylor, Three -dimensional analysis of eutectic grains in
hypoeutectic Al –Si alloys. Materials Science and Engineering A 392 (2005) 440 –448.
[20] B. Dybowski, B. Adamczyk -Cieślak, K. Rodak, I. Bednarczyk, A. Kiełbus , J. Mizera, The
microstructure of AlSi7Mg alloy in as cast condition . Solid State Phenomena 229 (2015) 3 –10.
[21] E. Tillová, M. Chalupová, L. Hurtalová, P. Pa lček, Scanning electron microscopy identification
of intermetallic phases in Al -Si cast alloys . Acta Metallurgica Slovaca 3 (2013) 196 –201.
[22] M. Gupta, S. Ling, Microstructure and mechanical properties of hypo/ hyper -eutectic Al –Si
alloys synthesized using a near -net shape forming technique. Journal of Alloys and Compounds
287 (1999) 284 –294.
[23] W.D. Callister Jr. (Ed.), Materials Science and Engineering: An Introduction, John Wiley and
Sons Inc, New York, (1994).
[24] X. Jian, Q. Han, Formation of hypereutectic silicon particles in hypoeutectic Al -Si alloys under
the influence of high -intensity ultrasonic vibration Vol.10 No.2 , March 2013, 118 -123.