O. TRUDONOSHYN ET al.: USE OF THE ABI TECHNIQUE TO MEASURE THE MECHANICAL PROPERTIES ...
427–431
USE OF THE ABI TECHNIQUE TO MEASURE THE
MECHANICAL PROPERTIES OF ALUMINIUM ALLOYS: EFFECT
OF HEAT-TREATMENT CONDITIONS ON THE MECHANICAL
PROPERTIES OF ALLOYS
UPORABA ABI TEHNIKE ZA MERJENJE MEHANSKIH
LASTNOSTI ALUMINIJEVIH ZLITIN: VPLIV POGOJEV
TOPLOTNE OBDELAVE NA MEHANSKE LASTNOSTI ZLITIN
Oleksandr Trudonoshyn1,2, Maxim Puchnin1, Olena Prach1,3
1Czech Technical University in Prague, Karlovo námìstí 13, 12135, Prague 2, Czech Republic
2Friedrich Alexander Universität Erlangen Nürnberg, Martenstraße 5, 91058 Erlangen, Germany
3Technische Universität Darmstadt, Karolinenplatz 5, 64289 Darmstadt, Germany
trudonoshyn@fhotm.kpi.ua
Prejem rokopisa – received: 2014-12-08; sprejem za objavo – accepted for publication: 2015-05-04
doi:10.17222/mit.2014.295
Effects of chemical composition and heat treatment on the microstructures and mechanical properties were investigated with
automated ball-indentation tests, scanning and transmission electron microscopy, and energy-dispersive X-ray analysis. In this
work, the automated ball-indentation (ABI) technique was compared with the standard mechanical tests. The ABI method is
based on load-controlled multiple indentations into a polished surface by a spherical indenter. The indentation depth is
progressively increased to the specified maximum limit with intermediate partial unloading. This technique allows us to
measure the yield strength, the stress-strain curve, the strength coefficient and the strain-hardening exponent. For all the test
materials and conditions, the ABI-derived results were in very good agreement with those obtained with conventional standard
test methods. We analyzed the effect of heat treatment on the alloys with different chemical compositions. Heat treatment leads
to changes in the mechanical properties of the alloys, which are the results of several processes.
Keywords: Al-alloys, heat treatment, tensile strength, yield strength, ABI hardness test
Vpliv kemijske sestave in toplotne obdelave na mikrostrukturo in mehanske lastnosti je bil preiskovan z avtomatiziranim
preizkusom trdote z vtiskovanjem kroglice, z vrsti~no in presevno elektronsko mikroskopijo in energijsko disperzijsko
rentgensko spektroskopijo. V tem delu je bila tehnika avtomatskega vtiskovanja kroglice (ABI) primerjana s standardnimi
mehanskimi preizkusi. ABI metoda temelji na kontrolirani obte`itvi pri ve~kratnem vtiskovanju krogli~nega telesa v polirano
povr{ino. Globina vtiskovanja postopoma nara{~a do maksimalne dolo~ene globine z vmesnimi razbremenitvami. Ta tehnika
omogo~a merjenje meje te~enja, krivulje raztezek-obremenitev, koeficienta trdnosti in eksponenta napetostnega utrjevanja. Za
vse preizku{ane materiale in pogoje, so se dobljeni ABI rezultati dobro ujemali z rezultati dobljenimi iz obi~ajnih metod
preizku{anja. Preu~evan je bil vpliv toplotne obdelave na zlitine z razli~no kemijsko sestavo. Toplotna obdelava povzro~i
spremembo mehanskih lastnosti zlitin, kar je posledica ve~ih procesov.
Klju~ne besede: Al-zlitine, toplotna obdelava, natezna trdnost, meja te~enja, trdota pri ABI preizkusih
1 INTRODUCTION
A large number of aluminum alloys have been deve-
loped for casting, but most of them are varieties of six
basic types (according to the AA Al alloy designation
system): Al-Cu (2XX.X), Al-Cu-Si (or Mg) (3XX.X),
Al-Si (4XX.X), Al-Mg (5XX.X), Al-Zn-Mg (7XX.X)
and Al-St (8XX.X).1 In this context, the alloys of the
Al-Mg-Si (6XXX) system have been widely used in
producing sheets, extruded parts and thin-wall castings.
It was reported by H. Sternau et al.2 that an
AlMg5Si2Mn alloy (HPDC) shows high mechanical
properties such as ductility (up to 18 %), yield strength
(up to 220 MPa) and tensile strength (up to 350 MPa),
compared with the other casting alloys.
When comparing the AlSi7Mg and AlMg5Si2Mn
casting alloys, the most evident difference is in the fact
that the highest strength of AlSi7Mg is achieved only
after the heat treatment, whereas AlMg5Si2Mn exhibits
its highest properties in the as-cast condition.
Heat-treatable Al-Mg-Si alloys are important for the
investigation because of the possible hardening process,
which leads to specific properties. The hardening effects
are shown when the dislocations interact with the preci-
pitates, which act as obstacles to the dislocation mo-
tion.1,3 It is well known that the ductility of such alloys
decreases with the increasing Si content. Brittle coarse Si
particles usually make further deformation difficult.3
In this regard, it is important to apply not only the
optimum chemical composition of the material but also
the optimum heat-treatment conditions. The main task of
this paper is to investigate the influence of heat treatment
on the mechanical properties and structure of Al-Mg-Si-
Mn alloys.
Materiali in tehnologije / Materials and technology 50 (2016) 3, 427–431 427
UDK 669.715:620.172:67.017 ISSN 1580-2949
Professional article/Strokovni ~lanek MTAEC9, 50(3)427(2016)
The ABI test is used to measure material properties
when a conventional technique cannot be applied
(welded parts, brittle materials, samples with a high po-
rosity and the parts currently used).4,5 As shown previ-
ously6, the results obtained with this method achieve
good compatibility with those of the conventional
methods.
2 MATERIALS AND METHODS
The chemical compositions of the evaluated alloys
are shown in Table 1.6
Two types of heat treatment were applied. The first
type was the solution treatment, carried out in an electric
resistance furnace. After the solution treatment, the
specimens were quenched at water at room temperature.
The second type of heat treatment was T6, combining
solution treatment at 570 °C (60 min), quenching in
water at room temperature and artificial aging at 175 °C
during various periods.
Indentation tests were carried out using a special
device (patent CZ 304637 B1), which, due to its design,
is capable of continuously recording the load and inden-
tation depth of the used indenter. The system includes: a
recording device, an analog-to-digital converter, a PC
with software and an Instron 5582 tensile-testing ma-
chine as the force-producing mechanism. The maximum
indentation load was 2.5 kN and the indenter diameter
was 5 mm. Plane-parallel samples were used for ABI
(automatic ball indentation) testing.
Series of measurements were carried out for all the
samples. The obtained HB hardness was compared with
the hardness, measured with a standard testing machine.
In the case of a good reproducibility of the results (an
error of the order of 10 %) from the obtained curve (Fig-
ure 1), values of the yield strength and tensile strength
were calculated.
The hardness was calculated with Equation (1):
HB
P
Dh
=
π
(1)
where HB is the Brinell hardness, P is the load (kN), D
is the diameter of the indenter (mm), h is the indentation
depth (mm) (Figure 1).
For the determination of the tensile strength (Rm), we
used Equation (2):7
R c HBm = ⋅ (2)
where c is the coefficient of uncertainty. For the pre-
sented series of alloys, we used the following value of
this coefficient – 2.8.6
For the determination of the yield strength (Rp0.2), the
methodology proposed in 7, together with Equation (3),
was used. The Meyer hardness was calculated with
Equation (4):
R c HMp0.2 = ⋅ (3)
HM
P
a
=
π 2
(4)
where c is the coefficient of uncertainty (2.8), HM is the
Meyer hardness and a is the contact radius.
Using the values of the indentation depth (h),
according to Equations (5) and (6), strain values () and
the contact radius (a) were determined. The value of
deformation for the yield stress was 0.2 %, by analogy
with the tensile tests.
O. TRUDONOSHYN ET al.: USE OF THE ABI TECHNIQUE TO MEASURE THE MECHANICAL PROPERTIES ...
428 Materiali in tehnologije / Materials and technology 50 (2016) 3, 427–431
Table 1: Nominal compositions of the alloys (Al – bal.), in mass fractions (w/% )
Tabela 1: Nominalna sestava zlitin (Al – ostalo), v masnih dele`ih (w/% )
Alloys Mg Si Mn Fe Ti Cu Zn Comment
AlMg6Mn (M3) 6.0 0.4 0.6 0.3 0.1 0.1 0.1 Al-1Mg2Si-5Mg
AlMg7SiMn (MS1) 7.0 1.0 0.6 0.02 0.1 0.05 0.05 Al-3Mg2Si-5Mg
AlMg7Si2Mn (MS2) 7.0 2.0 0.6 0.02 0.1 0.05 0.05 Al-6Mg2Si-3Mg
AlMg5Si2Mn (M59) 5.0 2.0 0.6 0.02 0.1 0.05 0.05 Al-6Mg2Si-1Mg
AlMg7Si3Mn (MS3) 7.0 3.0 0.6 0.02 0.1 0.05 0.05 Al-9Mg2Si-1Mg
AlMg7Si4Mn (MS4) 7.0 4.0 0.6 0.02 0.1 0.05 0.05 Al-10.5Mg2Si-0.5Si
AlMg7Si5Mn (MS5) 7.0 5.0 0.6 0.02 0.1 0.05 0.05 Al-10.5Mg2Si-1.5Si
AlSi7Mg (S1) 0.3 6.9 0.02 0.2 - 0.05 0.05 Al-7Si
Figure 1: Scheme for determining: a) contact radius, b) indentation
curve for the AlMg6Mn alloy
Slika 1: Shematski prikaz za dolo~anje: a) kontaktnega premera, b)
krivulja vtiskovanja pri zlitini AlMg6Mn
 =
h
D
(5)
a Dh h= − 2 (6)
3 RESULTS AND DISSCUSION
3.1 Mechanical properties
The values of the HB hardness and ABI tests are
summarized in Figure 2. Figure 4 represents the
dependencies of the load-indentation depth, which were
recorded in the ABI study. The differences between two
curves given in the diagrams (Figure 4) may be
connected with the changes in the value of the load (P),
leading to a diversity in the indentation depth and diffe-
rences in the hardness of the materials (HB).6
Figure 4 shows indentation curves of the alloys in
the as-cast state and after the heat treatment (T6).
As the result of the solution treatment, both HB and
tensile-strength values are significantly decreased
(except for the LP5 alloy). In addition, artificial aging
leads to an increase in all the mechanical properties of
the alloys.
The change during the heat treatment is the result of
several processes, which occur during the heating.
3.2 Processes which occur during homogenization
The first process is the eutectic spheroidisation (Fig-
ure 3a). A higher solution-treatment temperature leads
to a faster eutectic-lamella decomposition into smaller
segments and to the spheroidising effect. In 8,9 is pre-
O. TRUDONOSHYN ET al.: USE OF THE ABI TECHNIQUE TO MEASURE THE MECHANICAL PROPERTIES ...
Materiali in tehnologije / Materials and technology 50 (2016) 3, 427–431 429
Figure 2: Mechanical properties.*Classical method
Slika 2: Mehanske lastnosti.*Klasi~na metoda
Figure 3: Processes which occur during homogenization: a) spheroidisation of eutectic lamellas, b) formation of -(Al15(Mn,Fe)3Si2)
dispersoids, c) chemical composition (EDX) of Al15(Mn,Fe)3Si2 dispersoids
Slika 3: Procesi med homogenizacijo: a) sferoidizacija lamel evtektika, b) nastajanje disperzioidov -(Al15(Mn,Fe)3Si2), c) kemijska sestava
(EDX) disperzioidov Al15(Mn,Fe)3Si2
sented a model of the spheroidisation of eutectic lamellas
in the alloys of the Al-Mg-Si system. This process leads
to a decrease in the hardness of the alloys.
The second process is the dissolution of the primary
Mn-containing phases, forming dispersoids, which
include Mn, Si and Fe (Figure 3).10 Particle morphology
is shown in Figures 3b and 5b. These particles can be
identified as the -(Al15(Mn,Fe)3Si2) phase (Figure 3c).
A lack of coherence of phase -(Al15(Mn,Fe)3Si2) with
-Al probably affects (along with a disintegration of
eutectic cells) the decrease in the hardness of the alloys.
A dissolution of the ’-Mg9Si5 particles also occurs
during the homogenization.
The last process occurs in alloys MS4 and MS5. This
is a transformation of metastable acicular-shaped -pha-
ses to a more stable state due to diffusion processes.11–13
After the solution treatment, the excess silicon from the
-phase dissolves in the -aluminum solid solution.6 As
it can be seen from Table 2 and Figure 5f, this process
improves the hardness even after the homogenization.
3.3 Processes which occur during aging
The remaining processes occur in the solid solution
and consist of the formation of nanoscale precipitates via
a decomposition of a supersaturated solid solution
O. TRUDONOSHYN ET al.: USE OF THE ABI TECHNIQUE TO MEASURE THE MECHANICAL PROPERTIES ...
430 Materiali in tehnologije / Materials and technology 50 (2016) 3, 427–431
Table 2: Average compositions of Mn-containing phases in the MS4 and MS5 alloys, measured with EDX
Tabela 2: Povpre~na sestava faz, ki vsebujejo Mn v zlitinah MS4 in MS5, izmerjenih z EDX
Phase stoichiometry Condition
Chemical composition, in mass fractions (w/%)
O Mg Al Si Mn Fe Cu
-Al4(Mn,Fe)Si2 (acicular-shaped) AC 1.5 1.1 60.4 26.8 7.6 2.2 0.4
-Al5(Mn,Fe)Si (blocky-shaped, stable) ST 0.5 0.2 59.2 11.9 25.1 2.4 0.7
Figure 4: ABI indentation curves
Slika 4: ABI krivulje pri vtiskovanju
Figure 5: TEM bright-field images of the precipitates in the AlMgSiMn casting alloy: a) as-cast state, b) after homogenization, c) after artificial
ageing
Slika 5: TEM-posnetek (svetla polja) izlo~kov v AlMgSiMn livni zlitini: a) lito stanje, b) po homogenizaciji, c) po umetnem staranju
(SSSS) during aging (Figure 5). It is established that in
the Al-Mg-Si alloys, the decomposition of the super-
saturated solid solution takes place during aging and the
precipitation sequence is SSSS  GP-I  ''  ' 
-Mg2Si where GP-I is the Guiner-Preston zone.12,13
Solid-solution grains contain plate-like particles. One
of their sides is connected with curved lines, which
might be identified as dislocations.
Authors in 14,15 reported that these particles are
formed after natural aging as a result of a heterogeneous
nucleation of dislocations. They must be particles of the
’-Mg9Si5 phase. A direct relationship between the
dislocation density and the number of particles it is
shown in 14,15.
As can be seen from the graphs (Figures 4a and 4b),
heat treatment does not have a significant effect on the
mechanical properties (both the hardness and tensile
strength) of the alloys with extra magnesium.
According to the test results (Figure 4), heat treat-
ment of the alloys with extra silicon improves the
mechanical properties. With the increasing time of artifi-
cial aging (at 175 °C), the hardness of the alloys with
extra silicon grows. This is due to a sufficient amount of
silicon in solid solution needed for forming a larger
number of strengthening particles.
4 CONCLUSIONS
A higher solution-treatment temperature leads to a
faster eutectic-lamella decomposition into smaller seg-
ments and to the spheroidising effect, which causes a
sharp reduction in the mechanical properties.
Homogenization leads to a dissolution of the primary
Mn-containing phases and a formation of dispersoids
- (Al15(Mn,Fe)3Si2).
Homogenization leads to a transformation of the
metastable acicular-shaped -phase into a more stable
state ( or ) due to diffusion processes.
Artificial aging at 175 °C leads to a formation of
strengthening particles in -Al, causing an increase in
the hardness and tensile strength of the alloys. The
difference between the best results for the mechanical
properties of the alloys with excess Mg after the heat
treatment and the properties of the as-cast alloys, is not
significant.
Comparing the AlSi7Mg and AlMg5Si2Mn casting
alloys, the most evident difference is the fact that the
highest strength for AlSi7Mg is achieved only after the
heat treatment, whereas AlMg5Si2Mn exhibits its
highest properties in the as-cast condition.
Acknowledgments
The authors gratefully thank the Visegrad Fund and
DAAD for their support of the research. Trudonoshyn O.
and Prach O. would like to thank Mykhalenkov K. for
stimulating the investigations and helping us formulate
the discussion.
This work was supported by the Ministry of
Education, Youth and Sport of the Czech Republic, pro-
gram NPU1, project No LO1207 and SGS13/186/
OHK2/3T/12 – Research on the influence of surface
treatment on the improvement of service life and
reliability of exposed water-turbine components.
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