ISSN 00360295, Russian Metallurgy (Metally), Vol. 2014, No. 9, pp. 750–755. © Pleiades Publishing, Ltd., 2014.

Original Russian Text © Kh. Ri, V.G. Komkov, E.Kh. Ri, 2014, published in Metally, 2014, No. 5, pp. 80–86.

Effect of Alloying Elements on the Physicomechanical Properties

of Copper and Tin Bronze
Kh. Ri, V. G. Komkov, and E. Kh. Ri
Pacific State University, Khabarovsk, Russia
email: SL166@rambler.ru
Received October 10, 2013

Abstract—The effect of alloying elements (Al, Si, Mn, Zn, Ni, As) on the physicomechanical properties of
copper and tin bronze (6 wt % Sn) is studied. These alloying elements are found to increase the hardness and
the microhardness of the structural constituents of Cu–X alloys due to hardening the α solid solution and
eutectoid, and this effect of alloying elements is most effective in tin bronze. Alloyed copper and tin bronze
have a lower thermal conductivity and corrosion resistance as compared to plain copper and tin bronze.
DOI: 10.1134/S0036029514090158

INTRODUCTION Micro Flash device intended for determining the ther

Modern mechanical engineering needs materials mal diffusivity, the thermal conductivity, and the heat
that have a high strength and specialpurpose proper capacity of materials. All measurements were carried
ties (thermal conductivity, corrosion resistance, hard out using standard techniques. For structural investi
ness, etc.) that ensure longterm reliable operation gations, we used a Micro 200 optical microscope.
under various operating conditions. For such copper
based materials to be manufactured, one has to alloy RESULTS AND DISCUSSION
copper by proper elements, including zinc, alumi
num, and silicon [1]. The structure and composition When copper is alloyed with up to 7.5 wt % Al, its
of an alloy substantially affect its physicomechanical hardness HB increases monotonically (Fig. 1a). When
properties [2, 3]. The aim of this work is to study the the aluminum content increases to 12.5 wt %, the
effect of alloying elements (Al, Si, Mn, Zn, Ni, As) on hardness increases sharply, threefold as compared to
the physicomechanical properties (hardness, micro initial copper. The increase in the hardness of copper
hardness of structural constituents, thermal conduc containing up to 7.5 wt % Al can be explained by an
tivity, corrosion resistance) of copper and tin bronze increase in the microhardness of the α solid solution
(6 wt % Sn). (Fig. 1b). The hardness increment at >7.5 wt % Al can
be explained by eutectic solidification L → α + β [5],
the β phase of which undergoes the eutectoid transfor
EXPERIMENTAL mation β → α + γ2 (eutectoid α + γ2 has a high micro
To form samples, copper was overheated to a tem hardness, HV0.02 2652–2660 MPa; see Fig. 1b).
perature above the temperature threshold of an anom Thermal conductivity λ of copper alloyed with alu
alous change in the structuresensitive properties of minum decreases sharply when the aluminum content
liquid copper (1300°C) and was held for 5 min, and increases because of the distortion of the crystal lattice
alloying elements (AEs) were then introduced into of the α solid solution, the refinement of structural
copper. Melting was performed on a Paraboloid4 constituents, and the appearance of a eutectoid com
(TsNIITMASh) furnace in an alundum crucible under ponent in the structure (see Fig. 1a).
a layer of ground graphite powder for copper deoxida When copper is alloyed with silicon up to 3.0 wt %,
tion. After mixing and degassing, the melt was cooled its hardness HB increases monotonically and then
at a rate of 20°C/min in a pure argon atmosphere. increases sharply (Fig. 1a'). Microhardness HV0.02 of the
To study corrosion resistance, we used a weighing α solid solution increases from 783 to 1850 MPa as the
method. The samples were weighed on an ADB200 silicon content increases from 0 to 5 wt %. At >2 wt % Si
analytical balance before and after tests. A sample was in copper, the peritectic solidifies (L + α → P) and then
held in an aggressive medium (38% nitric acid solu undergoes the eutectoid decomposition P → α + γ with
tion) for 5 min [4]. Hardness HB was measured on a the formation of a eutectoid, which has a high micro
TSh2M hardness tester; microhardness HV0.02 was hardness as compared to the α solid solution (2000 MPa
measured on a PMT2 microhardness tester; and at 2.0 wt % Si and 2600–2670 MPa at 5.0 wt % Si).
thermal conductivity λ was measured on an LFA 457 Therefore, the increase in the hardness of copper

750
 EFFECT OF ALLOYING ELEMENTS ON THE PHYSICOMECHANICAL PROPERTIES 751

HB (a) (a') λ, W/(m K)

HB
100 HB 400
λ

λ
60 200

20 0
(b) (b')
HV0.02, MPa Eutectoid (α + γ2) Eutectoid (α + γ2)

2200
α sol. sol.

α sol. sol.
1400

600
(c) (c')
K, g/(cm2 h)
1.6

1.2

0.8
0 2 4 6 8 10 Al, wt % 0 1 2 3 Si, wt %

Fig. 1. Effect of the (a–c) aluminum or (a'–c') silicon content in copper on its hardness HB, thermal conductivity λ, microhard
ness HV0.02, and corrosion resistance K.

alloyed with silicon can be explained by an increase in Zinc and arsenic similarly affect the hardness and
the microhardness of the structural constituents. the microhardness of the α solid solution (Fig. 3).
According to the efficiency of increasing the hard
Thermal conductivity λ of copper decreases con ness and the microhardness of the α solid solution and
stantly with increasing silicon content because of the the eutectoid, AEs can be arranged in the following
distortion of the crystal lattice of the α solid solution, increasing order.
structure refinement, and the appearance of an addi At 2.0 wt % AE, according to the effect on
tional structural constituent (eutectoid) at 2–5 wt % Si. (a) hardness HB,
Nickel and manganese insignificantly increase the Al, Zn (40 HB) → Ni (42) → Si (45)
hardness of copper (Figs. 2a, 2a') due to an increase in → As (46) → Mn (50);
the microhardness of the α solid solution (Figs. 2b, 2b'). (b) microhardness of the α solid solution,
Thermal conductivity λ of copper decreases in the Zn, Ni (HV0.02 700 MPa) → As (780)
nickel and manganese alloying range under study. → Al, Mn (800) → Si (1030);

RUSSIAN METALLURGY (METALLY) Vol. 2014 No. 9

752 RI et al.

(a) (a')
HB

40

20
(b) (b')
HV0.02, MPa λ, W/(m K)

α sol. sol.
1000 α sol. sol. 200

λ λ
600 100

200 0
K, g/(cm2 h)
(c) (c')
1.6

1.2

0.8
0 1 2 3 Ni, wt % 0 1 2 3 Mn, wt %
Fig. 2. Effect of the (a–c) nickel or (a'–c') manganese content in copper on its hardness HB, microhardness HV0.02, thermal con
ductivity λ, and corrosion resistance K.

HB (a) HB (a')

40 40

20 20
HV0.02, MPa (b) HV0.02, MPa (b')
α sol. sol.
1000 600
α sol. sol.

600 200
K, g/(cm2 h) (c) K, g/(cm2 h) (c')

1.2 1.2

0.8 0.8

0.4 0.4
0 1 2 3 AAs, wt % 0 2 4 Zn, wt %
Fig. 3. Effect of the (a–c) arsenic or (a'–c') zinc content in copper on its hardness HB, microhardness HV0.02, and corrosion resis
tance K. The abscissa in (a–c) indicates the addition of master alloy AAs containing 6.93 wt % As in copper.

(c) microhardness of the eutectoid, (b) microhardness of the α solid solution,

Si (HV0.02 2000 MPa). Zn (HV0.02 800 MPa) → As (900) → Mn (950)
At 5.0 wt % AE, according to the effect on → Ni (1180) → Al (1300) → Si (1850);
(a) hardness HB,
(c) microhardness of the eutectoid,
Al (40 HB) → Ni (45) → As, Zn (48)
→ Mn (50) → Si (80); Si (HV0.02 2680 MPa).

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 EFFECT OF ALLOYING ELEMENTS ON THE PHYSICOMECHANICAL PROPERTIES 753

(a) (a')
HB λ, W/(m K) HB λ, W/(m K)

80 HB 140

60 100 120 200

40 λ 50 100 150
HB
20 0 80 100

0 60 λ 50
(b)
HV0.02, MPa 40 0
α sol. sol. (b')
HV0.02, MPa
1400 1400
α sol. sol.
1000 1200
4600 (c) 3800 (c')
Eutectoid Eutectoid
4200 3400

3800 3000
K, g/(cm2 h) (d) K, g/(cm2 h) (d')

1.2 1.2

0.8 0.8

0.4 0.4
0 1 2 3 Al, wt % 0 1 2 3 Si, wt %

Fig. 4. Effect of the (a–d) aluminum or (a–d') silicon content in tin bronze (6.0 wt % Sn) on its hardness HB, microhardness
HV0.02, thermal conductivity λ, and corrosion resistance K.

Thus, the hardness and the microhardness of low toid component, which has a high microhardness. The
alloy (2.0 wt % AE) copper are most effectively microhardness of the eutectoid in tin bronze (4000–
increased by Mn, Si, and As, the hardness of high 4200 MPa) is much higher than in aluminum bronze
alloy (5.0 wt % AE) copper is most effectively (2600–2680 MPa). The eutectoid appears at 2 wt % Al
increased by Mn or Si, and the microhardness of high in tin bronze and at >10 wt % Al in aluminum bronze.
alloy copper is most effectively increased by Si, Al, and This difference is likely to be caused by a tininduced
Ni. Hence, there is no direct correlation between the decrease in the solubility of aluminum in the α solid
hardness and the microhardness. Manganese and solution. In this case, alloyed eutectoid α + β
nickel, which form continuous solid solutions, most (Cu31Sn8) or α + γ2 forms.
strongly decrease the thermal conductivity.
As the silicon content increases to 5 wt %, hardness
Al, Si, Ni, and Zn most effectively influence the
hardness and the microhardness of the α solid solution HB of tin bronze increases sharply (Fig. 4a') despite an
in tin bronze. As the aluminum content increases to insignificant increase in the microhardness of the
5 wt %, the hardness of tin bronze increases from 50 to α solid solution (Fig. 4b'). Therefore, the main cause
70 HB and the microhardness of the α solid solution of the sharp increase in the hardness of tin bronze
increases from 1400 to 1700 MPa (Figs. 4a, 4b). The upon silicon alloying is an increase in the fraction of
microhardness of the eutectoid oscillates from 4200 to the eutectoid alloyed with silicon and tin and having a
4000 MPa in the aluminum content range 2–5 wt %. high microhardness (HV0.02 3200–3500 MPa;
Thus, the main factors that increase the hardness of Fig. 4c'). The eutectoid in a Cu–Si alloy is character
aluminumalloyed bronze are an increase in the ized by a microhardness of 2000 MPa at 2 wt % Si to
microhardness of the α solid solution and the eutec 2700 MPa at 5 wt % Si.

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754 RI et al.

HB λ, W/(m K) HB λ, W/(m K)
λ (a) (a')
80 30 80 λ 100
HB
HB
60 20 60 50

40 10 40 0
HV0.02, MPa (b) HV0.02, MPa (b')
Eutectoid
α sol. sol.
1800 1000
α sol. sol.
1400 600

K, g/(cm2 h) (c) K, g/(cm2 h) (c')

0.8 0.8

0.4 0.4
0 1 2 3 Ni, wt % 0 1 2 3 AAs, wt %

Fig. 5. Effect of the (a–c) nickel or (a'–c') arsenic content in tin bronze (6.0 wt % Sn) on its hardness HB, thermal conductivity λ,
microhardness HV0.02, and corrosion resistance K (AAs is the same as in Fig. 3).

At a content of 5 wt %, nickel also increases the As compared to a Cu–As alloy, arsenic in tin
hardness of tin bronze from 50 to 70 HB (Fig. 5a), and bronze decreases the hardness and the microhardness
the microhardness of the α solid solution increases of the α solid solution (Figs. 5a', 5b'). This decrease is
from 1400 to 1650 MPa. In contrast to a Cu–Ni alloy, likely to be caused by a sharp decrease in the solubility
a Cu–Sn–Ni alloy with 5 wt % Ni contains a eutec of tin in the α solid solution and by the formation of
brittle SnxAsyCuz compounds, which form in the
toid with a microhardness of 2000 MPa. structure as the arsenic content increases.
The effect of zinc on the hardness and the micro
(a)
hardness is more complex as compared to the consid
HB ered AEs (Figs. 6a, 6b). At 1 wt % Zn, hardness HB of
tin bronze increases insignificantly (by 5 HB), the
50 microhardness of the α solid solution remains almost
the same, and the microhardness of the eutectoid
40 increases sharply from 1870 to 2200 MPa. As the zinc
HV0.02, MPa (b) content increases to 5 wt %, the hardness of tin bronze
Eutectoid decreases insignificantly (to 50 HB), the microhard
ness of the α solid solution decreases from 1400 to
1050 MPa, and the microhardness of the eutectoid
1800 decreases to 1850 MPa. Hence, the decrease in the
α sol. sol. hardness of tin bronze with >1.0 wt % Zn is related to
1400 a decrease in the microhardness of the α solid solution
and the eutectoid, which was not detected in Cu–Zn
1000 alloys of a similar composition.
K, g/(cm2 h) (c) According to the efficiency of increasing the hard
ness of tin bronze and the microhardness of its struc
0.8 tural constituents, AEs can be arranged in the follow
ing increasing order. At 5.0 wt % AE, according to the
0.4 effect of AEs on
0 2 4 Zn, wt % (a) hardness HB,
Fig. 6. Effect of the zinc content in tin bronze (6.0 wt % Sn) As (45 HB) → Zn (55) → Al (70)
on its hardness, microhardness, and corrosion resistance. → Ni (75) → Si (130);

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 EFFECT OF ALLOYING ELEMENTS ON THE PHYSICOMECHANICAL PROPERTIES 755

(b) microhardness of the α solid solution, arsenic exert a similar effect. Mn, Si, and As most
As (HV0.02 1000 MPa) → Zn (1200) → Si (1450) effectively increase the hardness and the microhard
→ Ni, Al (1700); ness of lowalloy copper (2.0 wt % AE), and Si, Al,
and Ni most strongly increase the hardness and the
(c) microhardness of the eutectoid, microhardness of highalloy copper (5.0 wt % AE).
Zn, Ni (HV0.02 2000 MPa) → As (2100) (2) AEs most effectively influence the hardness and
→ Si (3500) → Al (4000). the microhardness of the α solid solution in tin bronze.
When the aluminum content increases to 5.0 wt %, the
Therefore, Al, Si, and Ni most effectively increase
hardness of tin bronze increases from 50 to 70 HB and
the hardness and the microhardness of the structural
the microhardness of the α solid solution increases
constituents in tin bronze.
from 1400 to 1700 MPa.
AEs Al, Si, Ni, and As substantially decrease the
thermal conductivity of tin bronze, and arsenic most (3) The microhardness of the eutectoid oscillates
sharply decreases the thermal conductivity. According from 4000 to 4500 MPa in the aluminum content
to the efficiency of decreasing the thermal conductiv range 2–5 wt %. Thus, the main factors that increase the
ity at 5 wt % AE, AEs can be arranged in the following hardness of tin bronze alloyed with up to 12.5 wt % Al
decreasing order: are an increase in the microhardness of the α solid solu
tion and the existence of a highhardness (4000–
Al(λ = 50 W/(m K)) → Si (25) → Ni (18) → As (12.5). 4200 MPa) eutectoid component. The eutectoid
As follows from the data in Figs. 1c, 1c', 2c, 2c', 3c, appears at 2 wt % Al in tin bronze and at >10 wt % Al
and 3c', all AEs decrease the corrosion resistance of in aluminum bronze of a similar composition. The
copper. According to the efficiency of decreasing the effect of other AEs on the hardness and the micro
corrosion resistance of copper at 5 wt % AE, AEs can hardness of the structural constituents of tin bronze
be arranged in the following order after Cu: was comprehensively studied.
CU (K = 0.82 g/(cm2 h)) → Zn (1.1) → Ni, As (1.2) (4) The thermal conductivity of copper an tin
→ Mn (1.3) → Al (1.7) → Si (2.0). bronze decreases constantly with alloying because of
the distortion of the crystal lattice of the α solid solu
Aluminum and silicon most strongly decrease the tion and the appearance of eutectoid components.
corrosion resistance of copper. In the case of tin (5) AEs degrade the corrosion resistance of copper
bronze, AEs similarly affect its corrosion resistance and tin bronze.
(see Figs. 4d, 4d', 5c, 5c'). Only zinc increases the cor
rosion resistance of tin bronze (Fig. 6c).
According to the efficiency of decreasing the cor ACKNOWLEDGMENTS
rosion resistance of tin bronze with 5 wt % AE, AEs This work was supported by the Ministry of Educa
can be arranged in the following order for bronze Cu + tion and Science of the Russian Federation, project
6 wt % Sn (0.8): no. 14.V37.21.0921.
Zn (K = 0.65 g/(cm2 h)) → Al (1.0)
→ Ni (1.1) → Si, As (1.2).
REFERENCES
Silicon and arsenic are seen to sharply decrease the
corrosion resistance of both copper and tin bronze. 1. N. R. Bochvar and N. P. Leonova, “Alloying of copper
The decrease in the corrosion resistance of copper and based alloys to produce film materials with specialpur
pose properties,” Tekhnol. Legkikh Splavov, No. 3, 71–
tin bronze is related to the refinement of the structural 76 (2009).
constituents and eutectoid solidification, which leads
to an increase in the length of phase interfaces. 2. B. A. Kolachev, V. A. Livanov, and V. I. Elagin, Materi
als Science and Heat Treatment of NonFerrous Metals
(Metallurgiya, Moscow, 1972).
CONCLUSIONS 3. V. G. Komkov, “Effect of alloying elements on the
structure of the liquid phase, solidification, and struc
(1) The hardness of copper increases as AEs ture formation in bronzes,” Vestn. TOGU, No. 4, 107–
increase to 7.5 wt % Al and 2.0 wt % Si due to an 114 (2012).
increase in the microhardness of the α solid solution.
4. I. L. Rozenfel’d and K. A. Zhigeleva, Rapid Corrosion
At 10–12.5 wt % Al and 2–5 wt % Si, the hardness of Test Methods for Metals (Metallurgiya, Moscow, 1966).
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zation of a highhardness eutectoid constituent, which 5. Phase Diagrams of Binary Metallic Systems: A Hand
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has a microhardness of 2600–2650 MPa for aluminum cow, 1997), Vol. 2.
bronze and 2000–2650 MPa for silicon bronze. Hard
ness HB of nickel and manganese bronze increases
monotonically to 42 and 47 HB, respectively. Zinc and Translated by K. Shakhlevich

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