ORIGINAL PAPER

Inter-relation of Microstructural Features and Dry Sliding WearBehavior of Monotectic Al–Bi and Al–Pb Alloys

Emmanuelle S. Freitas • Adrina P. Silva •

Jose E. Spinelli • Luiz C. Casteletti •

Amauri Garcia

Received: 21 February 2014 / Accepted: 15 April 2014

� Springer Science+Business Media New York 2014

Abstract Immiscible Al-based alloys of monotectic

composition have a particular feature of minority phases

embedded into the Al-rich matrix. The disseminated par-

ticles may act as in situ self-lubricating agents due to their

lower hardnesses compared with that of the Al-rich matrix,

favoring good tribological behavior. There is a lack of

systematic fundamental studies on the microstructural

evolution of monotectic alloys connected to application

properties. In the present investigation, the monotectic

Al-1.2wt%Pb and Al-3.2wt%Bi alloys have been chosen to

permit the effect of microstructural parameters on the wear

behavior to be analyzed. Directional solidification experi-

ments were carried out under transient heat flow conditions

allowing a large range of cooling rates to be experienced,

permitting a representative variation on the scale of the

microstructure to be examined. Samples of the monotectic

alloys having different interphase spacing, k, have been

subjected to microadhesive wear tests, and experimental

laws correlating the wear volume with the microstructural

interphase spacing and test time are proposed. It was found

that microstructural features such as the interphase spacing

and the morphology of the minority phase play a significant

role on the wear process and that for the alloys examined kexhibits opposite effects on the corresponding wear

volume.

Keywords Al–Bi alloy � Al–Pb alloy �Immiscible alloys � Microstructure � Self-lubricant � Wear

1 Introduction

Aluminum-based monotectic alloys such as Al–Pb and

Al–Bi have immiscible phases and microstructures charac-

terized by a minority soft phase following the morphology of

droplets and/or fibers embedded into the Al-rich matrix.

Numerous applications exist for composite materials having

particles, rods or filaments of one metal or compound dis-

persed uniformly within a matrix of another. The dispersed

component can be selected to provide characteristics such as

superconductivity, lubricity, catalytic activity or capability

for undergoing nuclear or electronic reactions, while the

matrix provides required bulk properties, including struc-

tural integrity and good tribological properties in a range of

temperatures [1–3]. In the case of Al-based monotectics,

practical applications include self-lubricated bearings,

electrical contact materials and the fabrication of porous

materials [4–8]. An important requirement for bearing alloys

is a low modulus of elasticity (E), which is achieved when

alloying the aforementioned soft metals (Pb, Bi) with Al [8].

The addition of either bismuth or lead to aluminum gives

rise to immiscible systems characterized by monotectic

reactions (L1[aAl ? L2), which occurs for the composition

of 3.2 wt%Bi at a temperature of 931 K or the composition of

E. S. Freitas � A. Garcia (&)

Department of Materials Engineering, University of Campinas

(UNICAMP), 13083-970 Campinas, SP, Brazil

e-mail: amaurig@fem.unicamp.br

A. P. Silva

Institute of Technology, Federal University of Para (UFPA),

Augusto Correa Avenue 1, 66075-110 Belem, PA, Brazil

J. E. Spinelli

Department of Materials Engineering, Federal University of Sao

Carlos (UFSCar), 13565-905 Sao Carlos, SP, Brazil

L. C. Casteletti

Department of Materials, Aeronautical and Automotive

Engineering, University of Sao Paulo (USP),

13566-590 Sao Carlos, SP, Brazil

123

Tribol Lett

DOI 10.1007/s11249-014-0338-8

1.2 wt%Pb at a temperature of 932 K. In both cases, the

resulting microstructures are formed by an Al matrix with a

dispersion of embedded solute particles [9–15]. The mag-

nitude and distribution of these particles will depend on the

rate of displacement of the solid/liquid interface during

solidification and the movement of such particles, which can

eventually be entrapped by the growth front. Silva et al.

examined the transient solidification of Al–Bi alloys of

hypomonotectic [9], monotectic [9, 10] and hypermonotec-

tic compositions [11]. These authors reported that Bi droplets

embedded into the Al matrix prevailed along the non-steady

solidification of the Al-3.2 wt%Bi monotectic alloy [10]. The

growth rate, v, varied during solidification from 0.6 to

1.0 mm/s. The classical relationship used for the growth of

lamellar eutectics: k2v = C has been shown to be adequate

for representing the evolution of k with the growth rate (k is

the interphase spacing, and C is a constant). The morphology

of Bi particles can be explained by the stability diagram

proposed by Ratke and Muller [12, 13], where the stability

limit of fibers has been defined as a function of temperature

gradients and solidification velocities. They suggested that

Bi droplets should prevail for larger solidification velocities

or smaller gradients. If low velocities or large gradients are

imposed, Bi fibers are expected to occur.

Due to its large segregation level, processing of immiscible

alloys is not considered an obvious task. Le and Zhao [14]

proposed an alternative process to minimize convective

effects and segregation along the extent of the miscibility gap.

According to these authors [14], the application of a static

magnetic field during directional solidification can cause a

more uniform distribution of the nucleation rate of the

minority phase as well as a decrease in the maximum size of

the droplets in front of the solidification interface, leading to a

final well-dispersed microstructure. Other study performed by

Silva et al. [15] has showed that the microstructures of the

Al-1.2 wt%Pb alloy can be formed either by well-dispersed

Pb-rich droplets in the aluminum rich matrix (v [ 1.1 mm/s)

or by fiber-like Pb-rich phase and string of pearls

(v \ 0.87 mm/s). The intermediate range of v has been shown

to be associated with a transition region characterized by a

mixture of both fibers and droplets.

An et al. [16] performed a surface treatment by electron

beam irradiation over a hypermonotectic Al-25wt%Pb

alloy. The overlapped zone beneath the melted zone has

been evaluated and exhibited good resistance to wear under

dry conditions. The irradiated Al–Pb alloy has been shown

to have a lubricious tribolayer covering almost the entire

affected surface, which allowed a lower coefficient of

friction at high load to be achieved when compared with

the non-irradiated Al–Pb alloy. Bhattacharya and Chatto-

padhyay [17] have used the Hall–Petch criterion and the

experimentally obtained relation between wear and hard-

ness for aluminum alloys to determine where the reduction

in grain size of aluminum during rapid solidification could

account for the reduction in wear for melt-spun Al–Pb

alloy samples. They reported that nanodispersed lead par-

ticles in aluminum induced significant improvement in

friction and wear characteristics. The authors also sug-

gested by the observed results that an adhesive type of wear

mechanism prevailed.

Lepper et al. [18] examined the wear behavior under dry

conditions of Al–Bi, Al–Pb and Al–Sn alloys containing 10

wt% of the self-lubricant component in all cases. The effects

of oxygen on the friction coefficient, due to differences in air

and vacuum (5.0 9 10-3 Pa), were observed to be much more

drastic than those of Sn, Bi and Pb. The final wear track vol-

ume (mm3) has been shown to be at least two times higher in

the case of the Al-10wt%Pb alloy tested in air.

Recent studies pointed out the effect of the grain size and of

the scale of microstructure parameters of metallic alloys, such

as the cellular, dendritic and interphase spacings, on the

resulting mechanical, corrosion and wear resistances of

metallic alloys [19–25]. Hall–Petch type correlations have

also been recently proposed describing the dependence of

microhardness on the cellular and primary dendritic arm

spacings [26, 27]. A recent study on a hypomonotectic Al–In

alloy has established a correlation between the wear volume

and the interphase spacing of In-rich particles [28]. The

lubricating effect of soft indium areas was shown to be

improved for coarser microstructures. Al–Bi and Al–Pb alloys

become potential alternative to Al–Sn bearing alloys due to

their availability, high strength-to-weight ratio and excellent

friction and wear properties. In spite of that, detailed studies

regarding the interaction between wear and microstructure of

these alloys cannot be found in the literature.

The present study was planned with a view to permitting

the effects of distribution of lead and bismuth-rich phases

(represented by the interphase spacing, k) on the wear behavior

of Al–Pb and Al–Bi monotectic alloys to be analyzed. Transient

directional solidification experiments were carried out provid-

ing a considerable range of interphase spacings to be analyzed

by microadhesive wear tests. Experimental inter-relations

between the wear volume, the time corresponding to the sliding

distance of wear tests and k are envisaged.

2 Experimental Procedure

The directional solidification setup, shown schematically in

Fig. 1a, allows transient conditions of solidification to be

attained during growth of monotectic Al-1.2wt%Pb and

Al-3.2wt%Bi alloys castings. This experimental system has

been detailed in a previous article [29]. Samples for metal-

lography and wear tests were extracted along the castings

length, at different positions from the cooled bottom, as

shown in Fig. 1b.

Tribol Lett

123

Longitudinal samples were electropolished and etched

with a solution of 0.5 % HF in water to reveal the micro-

structure. Image processing systems were used to measure

the interphase spacing (k), which was determined by

averaging the horizontal distance between the centers of

adjacent Pb/Bi particles, as shown schematically in Fig. 2

(about 50 readings for each examined position in the

castings). The microstructure was also characterized by

scanning electron microscopy (SEM).

Transverse samples were used in the microadhesive

(ball crater) wear tests in order to analyze the effect of k on

the wear scar volume (V). A schematic representation of

the used wear tester is shown in Fig. 3. During the tests, a

hard spherical bearing steel ball (AISI 52100, diameter of

25.4 mm and hardness of 818 HV) was rotated against the

sample, producing a wear crater. The ball is driven directly

by clamping the ball in a split drive shaft. The sample is

pressed into the rotating ball from the side by test loads

placed on the weight hanger. As the test duration (number

of rotations or sliding distance) increases the size of the

crater increases. The used ball sliding speed was

0.33 m s-1 (260 RPM), and the applied normal contact

load was 0.2 N. The volume V of a spherical wear scar was

calculated according to Eq. (1), where d is the crater

diameter, and R is the ball radius [20].

V ¼ p � d4

64 � R ð1Þ

Fig. 1 (a) Directional solidification apparatus employed in this work:

1 rotameter; 2 heat extracting bottom; 3 thermocouples; 4 computer

and data acquisition software; 5 data logger; 6 casting; 7 mold; 8

temperature controller; 9 electric heaters; 10 insulating ceramic

shielding; (b) representation of a columnar macrostructure, typical of

both alloys examined, and examples of samples extracted for

metallography and wear tests

Fig. 2 Schematic

representation of the methods

used for determining the

interphase spacing (k)

considering both

microstructural regions with the

prevalence of: (a) droplets and

(b) mixture of fiber-like phase

and string of pearls

Fig. 3 Schematic diagram of the sliding wear tester

Tribol Lett

123

The diameter was measured at least four times for each

wear crater. The tests were carried out under dry sliding

conditions [30–32] (i.e., in air and absence of lubricants) to

prevent any interfacial element from causing influences on

the feedback of the microstructure, and at 23 �C and a

relative humidity of 60 %.

3 Results and Discussion

The microstructure of the Al-3.2wt%Bi alloy casting is

formed by Bi droplets disseminated into the Al-rich matrix

along the entire casting and has been characterized by the

interphase spacing, k, along the casting length, as shown in

Fig. 4a. The cooling rate during the directional solidifica-

tion process is higher for regions closer to the cooled

bottom of the casting and decreases gradually toward the

top of the casting due to the increasing thermal resistance

of the solidified layer. The experimental cooling rate varied

in the range 3–30 K/s and the growth rate, v, from 1.0 to

2.4 mm/s [33]. This translates into an inverse effect on the

interphase spacing with smaller k at the bottom of the

casting, which increases progressively toward the top of the

casting, as shown in Fig. 4a. On the other hand, as depicted

(a)

0 10 20 30 40 50 60 70 800

10

20

30

40

50

60

70

80

90

100

110

120

Position, (mm)

Al-1.2 wt.% Pb

Droplets

Fibers

(b)

0 10 20 30 40 50 60 70 800

10

20

30

40

50

60

70

80

Position (mm)

Inte

rpha

se s

paci

ng, λ

(μm

)

Inte

rpha

se s

paci

ng, λ

(μm

)

Al- 3.2 wt.% Bi

Droplets

Droplets

Droplets

Fibers

Fig. 4 Evolution of k as a function of position (P) along the casting length for: (a) Al-3.2wt%Bi and (b) Al-1.2wt%Bi alloys. The error bars

indicate the minimum and maximum experimental values. Insets of SEM and optical images for specific positions are indicated by arrows

Tribol Lett

123

Ta

ble

1In

terp

has

esp

acin

g(k

),w

ear

crat

ers

and

wea

rv

olu

me

alo

ng

the

dir

ecti

on

ally

soli

difi

edA

l–P

ban

dA

l–B

isa

mp

les

Al-

1.2

wt%

Pb

Al-

3.2

wt%

Bi

P*

(mm

)V

(mm

3)

10

min

V(m

m3)

40

min

k(l

m)

P(m

m)

V(m

m3)

10

min

V(m

m3)

40

min

k(l

m)

D*

1.0

0.0

39

0.1

86

15

.31

.00

.02

40

.08

37

.1

5.0

0.0

46

0.1

43

21

.15

.00

.03

00

.08

81

5.8

10

.00

.03

20

.11

12

4.2

10

.00

.03

00

.08

62

2.4

15

.00

.03

20

.14

42

6.3

15

.00

.03

90

.13

92

7.4

20

.00

.02

80

.13

32

7.9

F*

30

.00

.02

70

.13

93

0.8

40

.00

.02

80

.16

33

6.6

50

.00

.02

60

.15

24

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.03

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Tribol Lett

123

in Fig. 4b, the directional solidification of the monotectic

Al–Pb alloy resulted in microstructures formed either by

Pb droplets corresponding to v [ 1.1 mm/s or by a fiber-

like morphology corresponding to v \ 0.87 mm/s [15].

For the wear tests, samples corresponding to the soft

phase particles with droplet shape were extracted from the

positions 1, 5, 10, 15 and 20 mm from the cooled surface of

both alloys castings. In addition, the evaluation of fiber-like

morphologies of the Al-1.2wt%Pb alloy demanded the

characterization of farther positions: 30, 40, 50 and 60 mm.

The experimental results of wear scar volume, in dry

conditions, are associated in Table 1 with position in

casting and the corresponding interphase spacing for 10

and 40 min tests.

With a view to permitting the wear behavior of samples

of different alloys having similar microstructural length

scale to be compared, 4 samples were selected (2 of each

alloy composition) having the interphase spacing parame-

terized at about 15 and 27 lm. The optical microstructures

of such samples are shown in Fig. 5, and the corresponding

results of scar wear volume as a function of the sliding

distance are depicted in Fig. 6. In any case, the wear volume

was found to be directly proportional to the sliding distance,

but was affected by the interphase spacing, k. The effect of

k was shown to be opposite when the wear behavior of the

two alloys is compared, i.e., for a same sliding distance the

P = 5mm; λ = 15.8µm; = 30.7K.s-1 λ = 27.4µm; = 12.7K.s-1

(a)

P = 1mm; λ = 15.3µm; = 13.9K.s-1 λ = 27.9µm; = 5.9K.s-1

(b)

P = 15mm;

P = 20mm;

Fig. 5 Typical microstructures of: (a) Al3.2wt%Bi and (b) Al1.2wt%Pb

alloys at different positions (P) along the casting length, standardized by

two levels of interphase spacing (k): about 15 and 27 lm. _T is the

experimental cooling rate determined at the moment that the monotectic

front passed by each position in casting

200 300 400 500 600 700 800 900

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24

Wea

r V

olu

me

(mm

3 )

Sliding Distance (m)

λ = 15 μm - Al-3.2wt. %Biλ = 27 μm - Al-3.2wt. %Biλ = 15 μm - Al-1.2wt. %Pbλ = 27 μm - Al-1.2wt. %Pb

Fig. 6 Wear volume as a function of the sliding distance during wear

tests of the Al 1.2wt%Pb and Al 3.2wt%Bi samples collected in the

casting at different positions (P) from the cooled surface of the casting

Tribol Lett

123

wear volume, V, of the Al-1.2wt%Pb alloy increases with

the decrease in k, while for the Al-3.2wt%Bi alloy, V

increases with the increase in k. This seems to be associated

with the distribution of the self-lubricating phase (droplets

of Pb and Bi) throughout the Al matrix, which is connected

to k (with smaller k, droplets having smaller diameters are

more homogeneously distributed) and to the hardness of

these droplets (Pb: 38.3HB and Bi: 94.2HB [34]). The

distribution of coarser Pb particles throughout the micro-

structure leads to lower wear volume, i.e., coarser droplets

are apparently capable of providing a more extensive and

continuous film thickness, thus favoring the lubricating

action. A similar result was reported in a recent study on a

monotectic Al–In alloy, i.e., the self-lubricating effect of

soft indium areas (In: 8.83HB) was shown to be improved

for coarser In droplets [28]. In contrast, for the Bi harder

droplets, it seems that the spreading of finer particles con-

tributes to a more efficient lubricating effect.

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

R2 = 0.99 Wea

r vo

lum

e, V

(m

m3 )

Interphase spacing, ( m)

10 minutes 20 minutes 30 minutes 40 minutes

Al-3.2wt.%Bi

R2 = 0.83

(a)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

V = 0.005.t - 0.105 [-1/2]

Al-3.2wt.% Bi - droplets

Wea

r vo

lum

e, V

(m

m3 )

-1/2 ( m-1/2)

10 minutes 20 minutes 30 minutes 40 minutes

(b)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

R2 = 0.78

R2 = 0.79

R2 = 0.94

Al-1.2wt.%Pb

Interphase spacing, ( m)

Wea

r vo

lum

e, V

(m

m3 )

10 minutes20 minutes30 minutes40 minutes

R2 = 0.85

(c)

0 4 8 12 16 20 24 28 32 36 40 0.00 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40

12 14 16 18 20 22 24 26 28 30 32 0.16 0.18 0.20 0.22 0.24 0.26 0.28 0.30

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

V = 0.003 + 0.016.t.[ -1/2]

Interphase spacing, -1/2 ( m-1/2)

Wea

r vo

lum

e, V

(m

m3 )

10 minutes 20 minutes 30 minutes 40 minutes

Al-1.2wt.% Pb - droplets

(d)

Fig. 7 (a, c) Wear volume as a function of k and (b, d) wear volume

as function of k-1/2 and wear test time (t): (10, 20, 30 and 40 min) for

the Al-1.2wt%Pb and Al-3.2wt%Bi alloys corresponding to the

casting regions with microstructures formed by Pb/Bi droplets

embedded in the Al-rich matrix. The error bars indicate the minimum

and maximum experimental values

0.16 0.20 0.24 0.28 0.32 0.36 0.400.02

0.04

0.06

0.08

0.10

0.12

Interphase spacing, -1/2 ( m-1/2)

Wea

r vo

lum

e, V

(m

m3 )

Al-3.2wt.% Bi - droplets - 20 minutes

Al-1.2wt.% Pb - droplets - 20 minutes

V20 min

= 0.003 + 0.016.t.( -1/2)

V20 min

= 0.005.t - 0.105.( -1/2)

Fig. 8 Comparison of wear volume against interphase spacing for

monotectic Al-1.2wt%Pb and Al-3.2wt%Bi alloys samples corre-

sponding to a wear test time of 20 min. The error bars indicate the

minimum and maximum experimental values

Tribol Lett

123

In order to incorporate the effects of both test time (or

sliding distance) and the microstructural interphase spacing

on the experimental crater wear volume, these results are

plotted jointly in Fig. 7. In Fig. 7a and c, the experimental

V values are plotted as a function of k for different test

times associated with the corresponding sliding distances

for samples of the Al-3.2wt%Bi and the Al-1.2wt%Pb

alloys, respectively. The dashed curves/lines represent

empirical fits to the experimental points. It can be seen that

the wear volume is significantly affected by both the test

time and k for both alloys, however, with an opposite trend

as aforementioned. Additionally, in the particular case of

the Al–Bi alloy, the effect of k on V seems to attain a limit,

i.e., for test times (t) higher than 30 min, a constant wear

volume is attained.

The correlation of V with the inverse of the square root

of k, shown in Fig. 7b and d for the Al-3.2wt%Bi and the

Al-1.2wt%Pb alloys, respectively, permitted linear exper-

imental equations relating V to both t and k to be derived.

These equations are plotted in Fig. 8 (with the test time

parameterized in 20 min), where the significant and

opposite role of the microstructural effect on the wear

volume can be clearly seen. However, for the Al-1.2wt%Pb

alloy, when the morphology of the Pb-rich phase change

from droplets to fibers, the interphase spacing seems not to

affect the wear volume, which is shown to depend only on

the test time, as shown in Fig. 9.

Figure 10a and b depicts images of the worn surfaces

after wear tests of 40 min in air of Al-3.2wt%Bi and

Al-1.2wt%Pb alloys samples, respectively. In both cases,

the droplets of the soft minority phase have been smeared

by the rotating ball during the wear tests resulting in an

aligned distribution of these phases (Spectrum 1). The

Al-rich matrix has also been subjected to distortion

(Spectrum 2), and the combined damage images suggest a

behavior typical of adhesive wear. Both soft phases are

insoluble in aluminum, but mutual solubility of metallic

couples is not a prerequisite for adhesion. As pointed out

by Landheer et al. [35], insoluble metals can also be

strongly adhered to each other. Aluminum has higher

strength and hardness than Bi and Pb (Al: 245HB; Pb:

38.3HB and Bi: 94.2HB [34] ), so the rupture of the formed

joints during sliding occurs by rupture of the minority

phases, which are transferred to the surface of the Al

matrix. This is a characteristic of surfaces worn by adhe-

sive wear [5]. The composition data inside the Tables of

Fig. 10 also indicate that a small amount of iron has been

incorporated into the alloys.

The results of this investigation show that the choice of

an Al-based monotectic alloy for bearing applications

should combine not only the alloy composition and the

24 28 32 36 40 44 48 52

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

0.22

0.24 W

ear

volu

me,

V (

mm

3)

10 minutes20 minutes30 minutes40 minutes

λ (μm)

Al-1.2wt.% Pb - fibers

Fig. 9 Wear volume as a function of k and wear test time for the

Al-1.2wt%Pb alloy corresponding to the casting regions with the

prevalence of fibrous Pb particles

(a)

Spectrum Al Fe Bi

Spectrum 1 53.7±2.7 0.25±0.02 46.0±2.8

Spectrum 2 76.5±3.8 0.60±0.04 22.9±1.4

(b)

Spectrum Al Fe Pb

Spectrum 1 73.4±3.7 2.0±0.14 24.6±1.5

Spectrum 2 96.3±4.8 3.6±0.25 0.02±0.001

Fig. 10 Secondary electron images of the worn surfaces and

compositions (EDX) of: (a) Bi-rich (spectrum 1); Al-rich (Spectrum

2) areas and (b) Pb-rich (spectrum 1); Al-rich (Spectrum 2) areas,

both for test times of 40 min, evidencing the action of the solid

lubricant (right areas) which has been smeared by the rotating ball

Tribol Lett

123

corresponding study of the worn surfaces but also an

appropriate comprehension and design of the final micro-

structure based on a specific morphology and on the length

scale of the microstructure.

4 Conclusions

The experimental correlation between wear data and

microstructure features has shown that the morphology of

the minority phase and the interphase spacing, k, plays a

significant role on the wear behavior of monotectic Al–Bi

and Al–Pb alloys. The effect of k was shown to be opposite

when the wear behavior of the two alloys is compared, i.e.,

for a same sliding distance, the wear volume of the

Al-1.2wt%Pb alloy increases with the decrease in k, while

for the Al-3.2wt%Bi alloy, V increases with the increase in k.

Acknowledgments The authors acknowledge the financial support

provided by FAPESP (Sao Paulo Research Foundation—Grants Nos.

2013/15478-3 and 2013/13030-5) and CNPq (The Brazilian Research

Council).

References

1. Johnston, M.H., McClure, J.C., Parr, R.A.: Preparation of

monotectic alloys having a controlled microstructure by direc-

tional solidification under dopant-induced interface breakdown.

US Patent 4198232A (1980)

2. Xu, Z., Shi, X., Wang, M., Zhai, W., Yao, J., Song, S., Zhang, Q.:

Effect of Ag and Ti3SiC2 on tribological properties of TiAl

matrix self-lubricating composites at room and increased tem-

peratures. Tribol. Lett. 53, 617–629 (2014)

3. Kumar, S., Sharma, V., Panwar, R.S., Pandey, O.P.: Wear

behavior of dual particle size (DPS) zircon sand reinforced alu-

minum alloy. Tribol. Lett. 47, 231–251 (2012)

4. Bhattacharya, D., Chattopaddhyay, K.: Microstructure and tri-

bological behavior of nano-embedded Al alloys. Scripta Mater.

44, 1677–1682 (2001)

5. Schouwenaars, R., Jacobo, V.H., Ortiz, A.: Microstructural aspects

of wear in soft tribological alloys. Wear 263, 727–735 (2007)

6. Gawarkiewicz, R., Wasilczuk, M.: Wear measurements of self-

lubricating bearing materials in small oscillatory movement.

Wear 263, 458–462 (2007)

7. Stobrawa, J., Ciura, L., Rdzawski, Z.: Rapidly solidified strips of

Cu–Cr alloys. Scripta Mater. 34, 1759–1763 (1995)

8. Yasuda, H., Ohnaka, I., Fujimoto, S., Sugiyama, A., Hayashi, Y.,

Yamamoto, M., Tsuchiyama, A., Nakano, T., Uesugi, K., Kishio,

K.: Fabrication of porous aluminum with deep pores by using Al–

In monotectic solidification and electrochemical etching. Mater.

Lett. 58, 911–915 (2004)

9. Silva, A.P., Spinelli, J.E., Garcia, A.: Microstructural evolution

during upward and downward transient directional solidification

of hypomonotectic and monotectic Al–Bi alloys. J. Alloys

Compd. 480, 485–493 (2009)

10. Silva, A.P., Spinelli, J.E., Garcia, A.: Thermal parameters and

microstructure during transient directional solidification of a

monotectic Al–Bi alloy. J. Alloys Compd. 475, 347–351 (2009)

11. Silva, A.P., Spinelli, J.E., Mangelinck-Noel, N., Garcia, A.: Micro-

structural development during transient directional solidification of a

hypermonotectic Al–Bi alloy. Mater. Des. 31, 4584–4591 (2010)

12. Ratke, L., Muller, A.: On the destabilization of fibrous growth in

monotectic alloys. Scripta Mater. 54, 1217–1220 (2005)

13. Ratke, L.: Theoretical considerations and experiments on

microstructural stability regimes in monotectic alloys. Mater. Sci.

Eng., A 413–414, 504–508 (2005)

14. Li, H., Zhao, J.: Directional solidification of an Al–Pb alloy in

a static magnetic field. Comp. Mater. Sci. 46, 1069–1075

(2009)

15. Silva, A.P., Garcia, A., Spinelli, J.E.: Microstructure morphologies

during the transient solidification of hypomonotectic and mono-

tectic Al–Pb alloys. J. Alloys Compd. 509, 10098–10104 (2011)

16. An, J., Shen, X.X., Lu, Y., Liu, B.: Microstructure and tribo-

logical properties of Al–Pb alloy modified by high current pulsed

electron beam. Wear 261, 208–215 (2006)

17. Bhattacharya, V., Chattopadhyay, K.: Microstructure and wear

behaviour of aluminium alloys containing embedded nanoscaled

lead dispersoids. Acta Mater. 52, 2293–2304 (2004)

18. Lepper, K., James, M., Chashechkina, J., Rigney, D.A.: Sliding

behavior of selected aluminum alloys. Wear 203–204, 46–56 (1997)

19. Goulart, P.R., Spinelli, J.E., Cheung, N., Garcia, A.: The effects

of cell spacing and distribution of intermetallic fibers on the

mechanical properties of hypoeutectic Al-Fe alloys. Mater.

Chem. Phys. 119, 272–278 (2010)

20. Spinelli, J.E., Ferreira, I.L., Garcia, A.: Influence of melt con-

vection on the columnar to equiaxed transition and microstructure

of downward unsteady-state directionally solidified Sn–Pb alloys.

J. Alloys Compd. 384, 217–226 (2004)

21. Rosa, D.M., Spinelli, J.E., Osorio, W.R., Garcia, A.: Effects of

cell size and macrosegregation on the corrosion behavior of a

dilute Pb–Sb alloy. J. Power Sources 162, 696–705 (2006)

22. Abdi, B.R., Besharati, G.M.K., Akbari, M.: Mechanical proper-

ties, corrosion resistance, and microstructural changes during

friction stir processing of 5083 aluminum rolled plates. Mater.

Manuf. Process. 27, 636–640 (2012)

23. Garcia, L.R., Osorio, W.R., Peixoto, L.C., Garcia, A.: Mechanical

properties of Sn–Zn lead-free solder alloys based on the micro-

structure array. Mater. Charact. 61, 212–220 (2010)

24. Cruz, K.S., Meza, E.S., Fernandes, F.A.P., Quaresma, J.M.V.,

Casteletti, L.C., Garcia, A.: Dendritic arm spacing affecting

mechanical properties and wear behavior of Al–Sn and Al–Si

alloys directionally solidified under unsteady-state conditions.

Metall. Mater. Trans. A 41A, 972–984 (2010)

25. Martin, E., Azzi, M., Salishchev, G.A., Szpunar, J.: Influence of

microstructure and texture on the corrosion and tribocorrosion

behavior of Ti-6Al-4V. Tribol. Int. 43, 918–924 (2010)

26. Brito, C., Siqueira, C.A., Spinelli, J.E., Garcia, A.: Effects of cell

morphology and macrosegregation of directionally solidified Zn-

rich Zn Cu alloys on the resulting microhardness. Mater. Lett. 80,

106–109 (2012)

27. Kaya, H., Boyuk, U., Cadırlı, E., Maraslı, N.: Influence of growth

rate on microstructure, microhardness and electrical resistivity of

directionally solidified Al-7wt%Ni hypoeutectic alloy. Met.

Mater. Int. 19, 39–44 (2013)

28. Freitas, E.S., Spinelli, J.E., Casteletti, L.C., Garcia, A.: Micro-

structure-wear behavior correlation on a directionally solidified

Al–In monotectic alloy. Tribol. Int. 66, 182–186 (2013)

29. Rosa, D.M., Spinelli, J.E., Ferreira, I.L., Garcia, A.: Cellular/

dendritic transition and microstructure evolution during transient

directional solidification of Pb–Sb alloys. Metall. Mater. Trans. A

39A, 2161–2174 (2008)

30. Savaskan, T., Bican, O.: Dry sliding friction and wear prop-

erties of Al-25Zn-3Cu-3Si alloy. Tribol. Int. 43, 1346–1352

(2010)

31. Dong, Y.J., Wang, H.M.: Microstructure and dry sliding wear

resistance of laser clad TiC reinforced Ti–Ni–Si intermetallic

composite coating. Surf. Coat. Technol. 204, 731–735 (2009)

Tribol Lett

123

32. Cui, G., Niu, M., Zhu, S., Yang, J., Bi, Q.: Dry-sliding tribo-

logical properties of bronze-graphite composites. Tribol. Lett. 48,

111–122 (2012)

33. Freitas, E.S.: Development of correlations between solidification

microstructures and wear and corrosion resistances. Ph.D. thesis,

University of Campinas—UNICAMP, Campinas –Sao Paulo (2013)

34. http://www.webelements.com. Accessed 16 January 2014

35. Landheer, D., Dackus, A.J.G., Klostermann, J.A.: Fundamental

aspects and technological implications of the solubility concept

for prediction of running properties. DGM—Hauptversammlung,

Berlin (1980)

Tribol Lett

123