This work presents the experimental results concerning the behavior on heat treatment of on aluminum based alloy. The laboratory level experiments achieved on samples of ATN-Si10Cu4 (4145 series) alloy illustrate the variation of properties depending on the variation of heat treatment technological parameters specific to different heat treatment. We have experimented more variants of heat treatment in order to establish the optimal variant treatment. The samples were characterized by HB hardness and microstructure analysis

Elisabeta VASILESCU

Simona BOICIUC

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

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19 76
 
 
THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 2 – 2007, ISSN 1453 – 083X 
 
 
 
 
STUDY OF HEAT TREATMENT INFLUENCE ON  
ALUMINUM -BASED ALLOY ATN-Si10Cu4 
 
Elisabeta VASILESCU, Simona BOICIUC 
 “Dunărea de Jos” University of Galaţi 
email: elisabeta.vasilescu@yahoo.com 
 
ABSTRACT 
 
This work presents the experimental results concerning the behavior on heat 
treatment of on aluminum based alloy. The laboratory level experiments achieved 
on samples of ATN-Si10Cu4 (4145 series) alloy illustrate the variation of properties 
depending on the  variation of heat treatment technological parameters specific to 
different heat treatment. We have experimented more variants of heat treatment in 
order to establish the optimal variant treatment. The samples were characterized by 
HB hardness and microstructure analysis. 
 
KEYWORDS: heat treatment, quenching in solution and heat ageing, 
aluminum based alloy. 
 
 
1. Introduction 
 
ALUMINUM, the second most plentiful 
metallic element on earth, became an economic 
competitor in engineering applications as recently as 
the end of the 19th century. It was to become a metal 
for its time. The emergence of three important 
industrial developments would, by demanding 
material characteristics consistent with the unique 
qualities of aluminum and its alloys, greatly benefit 
growth in the production and use of the new metal. 
The properties of aluminum that make this metal 
and its alloys the most economical and attractive for a 
wide variety of uses are appearance, light weight, 
fabricability, physical properties, mechanical 
properties, and corrosion resistance. 
Aluminum has a density of only 2.7g/cm3. It can 
display excellent corrosion resistance in most 
environments, including atmosphere, water, 
petrochemicals, and many chemical systems. 
Aluminum surfaces can be highly reflective. 
Aluminum typically displays excellent electrical and 
thermal conductivity, but specific alloys have been 
developed with high degrees of electrical resistivity. 
It is nonferromagnetic, a property of importance in 
the electrical and electronics industries [1, 2, 3, 4, 5, 
6]. 
It is convenient to divide aluminum alloys into 
two major categories: casting compositions and 
wrought compositions. A further differentiation for 
each category is based on the primary mechanism of 
property development. Many alloys respond to 
thermal treatment based on phase solubilities. 
These treatments include solution heat treatment, 
quenching, and precipitation, or age, hardening. For 
either casting or wrought alloys, such alloys are 
described as heat treatable. A large number of other 
wrought compositions rely instead on work hardening 
through mechanical reduction, usually in combination 
with various annealing procedures for property 
development (Fig.1). These alloys are referred to as 
work hardening. Some casting alloys are essentially 
not heat treatable and are used only in as-cast or in 
thermally modified conditions unrelated to solution or 
precipitation effects [1, 2]. 
1xxx Series. Aluminum of 99.00% or higher 
purity has many applications, especially in the 
electrical and chemical fields. These grades of 
aluminum are characterized by excellent corrosion 
resistance, high thermal and electrical conductivities, 
low mechanical properties, and excellent workability. 
Moderate increases in strength may be obtained by 
strain hardening. Iron and silicon are the major 
impurities. Typical uses include chemical equipment, 
reflectors, heat exchangers, electrical conductors and 
capacitors, packaging foil, architectural applications, 
and decorative trim.  
2xxx Series. Copper is the principal alloying 
element in 2xxx series alloys, often with magnesium 
as a secondary addition. These alloys require solution 
heat treatment to obtain optimum properties; in the 
solution heat-treated condition, mechanical properties 
are similar to, and sometimes exceed, those of low-
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carbon steel. In some instances, precipitation heat 
treatment (aging) is employed to further increase 
mechanical properties.  
This treatment increases yield strength, with 
attendant loss in elongation; its effect on tensile 
strength is not as great. 
 
 
 
Fig.1. Al alloys and treatment classification system 
 
Table 1. Characterization of aluminum based alloys 
 
Alloy 
series Composition 
σc 
[MPa] 
σr 
[MPa] 
ε 
[%] Notes 
1000 Pure Al 30 - 100 100 - 135 Up to 50 Foil, decoration, electrical conductors 
2000 ∼4.5%Cu (+Mn, Si, Mg) age - hardened Up to 480 Up to 520 5 - 20
General purpose forgings and 
extrusions, esp.airframes 
3000 ∼1%Mn, Mg cold - worked Up to 215 Up to 290 5 
Ductile sheet for cladding trucks, 
trailers; food containers, drink cans. 
4000 
12%Si (+Mg, Ni, 
Cu) forgeable, age - 
hardened 
∼295 ∼325 0.5 IC engine pistons 
5000 ∼5%Mg (+Cr, Mn)cold - worked Up to 350 Up to 415 15 
Good formability and weldability; 
excellent corrosion resistance; 
structural applications, esp. marine. 
6000 Up to 1% Mg – Si, age - hardened ∼275 ∼310 12 Hot extrusions; window frames. 
7000 
Up to 8% Zn (+Mg, 
Cu, Cr) age - 
hardened 
500 575 11 Highest strength alloys; aircraft structures. 
8000 Other, e.g. up to 2.5% Li    Novel and specialist alloys 
Cast 
Near Al – 13%Si 
eutectic + 0.01% 
Na 
Up to 200 Up to 300 2 - 5 Automotive castings; can age – harden if Cu and Mg added. 
 
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N0. 2 – 2007, ISSN 1453 – 083X 
 
 
The alloys in the 2xxx series do not have as good 
corrosion resistance as most other aluminum alloys, 
and under certain conditions they may be subject to 
intergranular corrosion. Therefore, these alloys in the 
form of sheet usually are clad with a high-purity 
aluminum or with a magnesium-silicon alloy of the 
6xxx series, which provides galvanic protection of the 
core material and thus greatly increases resistance to 
corrosion. Alloys in the 2xxx series are particularly 
well suited for parts and structures requiring high 
strength-to-weight ratios and are commonly used to 
make truck and aircraft wheels, truck suspension 
parts, aircraft fuselage and wing skins, and structural 
parts and those parts requiring good strength at 
temperatures up to 150 °C (300 °F). Except for alloy 
2219, these alloys have limited weldability, but some 
alloys in this series have superior machinability. 
3xxx Series. Manganese is the major alloying 
element of 3xxx series alloys. These alloys generally 
are non-heat treatable but have about 20% more 
strength than 1xxx series alloys. Because only a 
limited percentage of manganese (up to about 1.5%) 
can be effectively added to aluminum, manganese is 
used as major element in only a few alloys. However, 
three of them--3003, 3X04, and 3105--are widely 
used as general-purpose alloys for moderate-strength 
applications requiring good workability. These 
applications include beverage cans, cooking utensils, 
heat exchangers, storage tanks, awnings, furniture, 
highway signs, roofing, siding, and other architectural 
applications. 
4xxx Series. The major alloying element in 4xxx 
series alloys is silicon, which can be added in 
sufficient quantities (up to 12%) to cause substantial 
lowering of the melting range without producing 
brittleness. For this reason, aluminumsilicon alloys 
are used in welding wire and as brazing alloys for 
joining aluminum, where a lower melting range than 
that of the base metal is required. Most alloys in this 
series are non-heat treatable, but when used in 
welding heat-treatable alloys, they will pick up some 
of the alloying constituents of the latter and so 
respond to heat treatment to a limited extent. The 
alloys containing appreciable amounts of silicon 
become dark gray to charcoal when anodic oxide 
finishes are applied and hence are in demand for 
architectural applications. Alloy 4032 has a low 
coefficient of thermal expansion and high wear 
resistance, and thus is well suited to production of 
forged engine pistons. 
5xxx Series. The major alloying element in 5xxx 
series alloys is magnesium. When it is used as a 
major alloying element or with manganese, the result 
is a moderate-to-high-strength work-hardenable alloy. 
Magnesium is considerably more effective than 
manganese as a hardener, about 0.8% Mg being equal 
to 1.25% Mn, and it can be added in considerably 
higher quantities. Alloys in this series possess good 
welding characteristics and good resistance to 
corrosion in marine atmospheres. However, certain 
limitations should be placed on the amount of cold 
work and the safe operating temperatures permissible 
for the higher-magnesium alloys (over about 3.5% for 
operating temperatures above about 65 °C, or 150 °F) 
to avoid susceptibility to stress-corrosion cracking. 
Uses include architectural, ornamental, and 
decorative trim; cans and can ends; household 
appliances; streetlight standards; boats and ships, 
cryogenic tanks; crane parts; and automotive 
structures. 
6xxx Series. Alloys in the 6xxx series contain 
silicon and magnesium approximately in the 
proportions required for formation of magnesium 
silicide (Mg2Si), thus making them heat treatable. 
Although not as strong as most 2xxx and 7xxx alloys, 
6xxx series alloys have good formability, weldability, 
machinability, and corrosion resistance, with medium 
strength. Alloys in this heat-treatable group may be 
formed in the T4 temper (solution heat treated but not 
precipitation heat treated) and strengthened after 
forming to full T6 properties by precipitation heat 
treatment. Uses include architectural applications, 
bicycle frames, transportation equipment, bridge 
railings, and welded structures. 
7xxx Series. Zinc, in amounts of 1 to 8% is the 
major alloying element in 7xxx series alloys, and 
when coupled with a smaller percentage of 
magnesium results in heat-treatable alloys of 
moderate to very high strength. Usually other 
elements, such as cooper and chromium, are also 
added in small quantities. 7xxx series alloys are used 
in airframe structures, mobile equipment, and other 
highly stressed parts. Higher strength 7xxx alloys 
exhibit reduced resistance to stress corrosion cracking 
and are often utilized in a slightly overaged temper to 
provide better combinations of strength, corrosion 
resistance, and fracture toughness. 
 
2. Experimental conditions 
 
The experiments have been made on ATN-
Si10Cu4 aluminum alloy (4145 series) having 
chemical composition shown in table 2.  
 
Table 2. Chemical composition of  Al-Si-Cu- Mg 
 
Cu Fe Mn Ni Zn Si Mg Pb Al 
4.5 0.93 0.61 0.67 3.0 11.05 0.84 0.102 rest 
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FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 2 – 2007, ISSN 1453 – 083X 
 
 
 
 
The laboratory experiments have been made of 
the specific heat treatments: quenching in solution 
and heat ageing with different experimental 
conditions. 
The researches shown the optimal technological 
parameters into experimental conditions, fig. 2: 
 
 The optimal temperature for quenching in 
solution; 
 Time maintaining at optimal temperature for 
quenching in solution; 
 Optimal time and temperature for ageing. 
 
100
200
300
400
600
500
700
t[0C]
τ[h]
*
**
***
****  
Fig.2. Experimental conditions for heat treatment: * - temperature for quenching in solution  
300°C, 350°C, 400°C, 450°C, 500°C, 550 °C; ** - Time maintaining for quenching in solution,  
5 – 8 min/mm in thickness; *** - ageing temperature 120°, 150°, 200°C;  
**** - Time maintaining 1, 3, 6 ore. 
 
The effect of heat treatment on alloy structure 
and physical-mechanical properties was valued by 
hardness measurements (Brinell method, F=62.5 daN, 
bowl diameter D=2.5mm, maintaining time τ=15s ). 
Analyzing this experimental results (Fig.3 and 
Fig.4) we considered that the optimal temperature is 
480 °C and the maintaining time is 2 h. 
 
 
50
55
60
65
70
75
80
300 350 400 450 500 550
Temperature, [0C]
H
ar
dn
es
 H
B
, [
da
N
/m
m2 ]
 
Fig.3. The influence of quenching in solution  temperature  on hardness 
 
 
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N0. 2 – 2007, ISSN 1453 – 083X 
 
 
50.0
55.0
60.0
65.0
70.0
75.0
80.0
0.5 1 3 6
Time, [h]
H
ar
dn
es
 H
B
, [
da
N
/m
m2 ]
 
Fig.4. The influence of time maintaining at  
480 °C (optimal one) on hardness. 
0.0
20.0
40.0
60.0
80.0
100.0
2 48 120 182 336
Time, [h]
H
ar
dn
es
 H
B
, [
da
N
/m
m2
]
 
Fig.5. The influence of time maintaining on alloy 
natural ageing in state of quenching in solution 
at 480 °C and 2 h. 
 
 
 
 
 
0.0
20.0
40.0
60.0
80.0
100.0
120.0
1 3 6
Time, [h]
H
ar
dn
es
 H
B
, [
da
N
/m
m2
]
 
 
a 
0.0
20.0
40.0
60.0
80.0
100.0
120.0
1 3 6
Time, [h]
 
 
b 
 
 
 
0
20
40
60
80
100
120
140
1 3 6
Time, [h]
H
ar
dn
es
 H
B
, [
da
N
/m
m2
]
 
c 
Fig.6. The influence of time maintaining on alloy artificial ageing at  
different temperatures:a - 120°C; b - 150°C; c - 200°C. 
 
 
 
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THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI. 
FASCICLE IX. METALLURGY AND MATERIALS SCIENCE 
N0. 2 – 2007, ISSN 1453 – 083X 
 
 
 
 
3. Microstructural aspects 
 
Figure gives the microstructural aspect of the Al alloy to enlargement power 250x, attack with 5% HF. 
 
 
The microstructure of the Al alloy after quenching in 
solution  
 
The microstructure of the Al alloy after quenching in 
solution and artificial ageing at 120°C for 6hours  
 
The microstructure of the Al alloy after quenching in 
solution and artificial ageing at 150°C for 3 hours  
 
The microstructure of the Al alloy after quenching in 
solution and artificial ageing at 200°C for 3hours  
 
 
4. Conclusions 
 
The experimental conditions applied shown 
that this alloy is sensible at structural and properties 
modifications (considering hardness as a measure for 
the variation of the mechanical properties). 
It was established for the alloy with given 
chemical composition (table 1) the optimal 
temperature of quenching in solution - 480 °C for 
maintaining time 2 hours. The increase of the 
temperature over this value or the increase of the 
maintaining time lead to the decrease of hardness. 
Concerning the heat treatment of ageing it comes out 
that at natural ageing the increase of maintaining time 
over 5 – 6 days, didn’t influence the hardness, which 
become constant. 
The artificial ageing achieved at different 
temperatures and different maintaining times show: 
 The maximum hardness (120 HB) was 
achieved at 200 °C, this value couldn’t be achieved  
over a maintaining time of 6 hours for 120 °C and 
150 °C. 
 The maintaining time for artificial ageing at 
optimal temperature 200°C, mustn’t prolonge over 3 
hours, because the hardness decreases. 
 
References 
 
[1]. ASM HANDBOOK – Volume 2 – Properties and selection: 
Nonferrous alloys and special – purpose materials, 1990. 
[2]. S. G. Roberts – Engineering “C” – High performance alloys, 
Department of Materials, University of Oxford. 
[3]. Dulamita T, Florian E – Tratamente termice şi termochimice, 
E.D.P. Bucureşti, 1982. 
[4]. Popescu N, şa – Ştiinţa materialelor vol 2, Editura Fair 
Partners, Bucureşti 1999. 
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Study of Heat Treatment Influence on Aluminum - Based Alloy ATN-Si10Cu4

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Study of Heat Treatment Influence on Aluminum - Based Alloy ATN-Si10Cu4

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