Wetting angle and infiltration velocity of Zr base

bulk metallic glass composite

Xidong Hui *, Jialing Yu, Meiling Wang, Wei Dong, Guoliang Chen

State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China

Available online 24 March 2006

Abstract

The contact angles of Zr47Ti13Cu11Ni10Be16Nb3 alloy on tungsten substrate were measured by sessile drop technique at the temperature range

from 1023 to 1323 K and different processed time. Based on the morphology of the melt drop, the surface tension as function of processing

temperature and holding time was obtained. Diffusion band was observed at the fringe of metallic drop, which confirms that the wetting between

the melt and tungsten belongs to reactive wetting. The relationship between the flow velocity of melt and processing parameters, such as

infiltration pressure, volume fraction of fibers and the filtration length, was calculated comprehensively.

q 2006 Elsevier Ltd. All rights reserved.

Keywords: A. Composites; B. Glasses, metallic; C. Joining

1. Introduction

Most monolithic BMGs have been proved to fail catastrophi-

cally by rapid propagation of localized shear bands during

unconstrained deformation at room temperature. To overcome

this drawback, BMGs matrix composite reinforced with fibers

and particulates have been fabricated by infiltration casting [1–4]

and suction casting [5,6]. It is shown that reinforcements indeed

restrict shear band propagation and promote the generation of

multiple shear bands and additional fracture surface area [3,5].

BMGsmatrix composite have exhibited significant improvement

of plastic strain [4] and dynamic deformation [7,8] in compared

with the monolithic BMG alloys.

Among all the preparation methods of BMGS matrix

composite, the infiltration process seems to be the most

efficient and promising pathway. It is especially suitable for the

fabrication of composites containing high volume fraction of

reinforcement. The quality of BMGs matrix composite is not

only defined by the properties of the matrix and the

reinforcement material but also by the controlling of infiltration

conditions, such as infiltration temperature, pressure, infiltra-

tion time. In fact, these parameters are essentially determined

by the wetability and interface reaction of the metallic melt

with the fibers. Jan Schroers et al. [9] investigated the reaction

0966-9795/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.

doi:10.1016/j.intermet.2006.01.037

* Corresponding author. Tel.: C86 814 863 9957; fax: C86 10 62332508.

E-mail address: huixd01@hotmail.com (X. Hui).

of the bulk glass forming alloy Zr41Ti14Cu12Ni10Be23 (vit 1)

with W, Ta, Mo, AlN, Al2O3, Si, graphite, and amorphous

carbon by using sessile drop technology. They presented a

systemic evaluation for the above materials as reinforcement

according to the wetability and interface reaction. Base on this

fundamental work of the interface characterization, they

prepared many kinds of BMGs matrix composite reinforced

by metallic fibers and particulate. In this work, we investigate

the wetting behavior of metallic glass alloy Zr47Ti13Cu11Ni10-Be16Nb3 with tungsten. The addition of Nb is believed to

improve the interface cohesion and to the compress strength.

To our knowledge, no experimental data of the contact angle

and surface tension of this Zr-based BMGS matrix composite

has been reported.

2. Experimental procedure

Zr47Ti13Cu11Ni10Be16Nb3 alloy was prepared by

arc-melting the constituents with a purity ranging from 99.5 to

99.99% in a Ti-gettered argon atmosphere. The samples with a

diameter of 2 mm were prepared by inductively heating in

vacuum (!3!10K5 m bar) and injected into coppermold. Then

Zr-based disc with the height of 2 mm was cut from the as-cast

rod. The melting point of this kind of alloy was measured to be

921 K. The tungsten substrate use in this work is 20 mm!20 mm! 20mm plate with the purity higher than 99.9 wt%.

Experimental measurement of the contact angle and surface

tension of bulk metallic glass forming alloy on tungsten

substrate were conducted by using sessile drop technique.

Before the Zr-based disc and tungsten substrate were set in the

Intermetallics 14 (2006) 931–935

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X. Hui et al. / Intermetallics 14 (2006) 931–935932

chamber of experimental apparatus, they were firstly cleaned in

an ultrasonic bath of acetone, followed by ethanol. Then they

were heated with a molybdenum furnace at a rate of 20 K/s and

high vacuum of 3.0!10K3 Pa. The alloy was melted and

processed at the temperature from 1023 to 1323 for different

times. In order to hold the drop morphology, the melt drop was

cooled in molybdenum furnace after it was wetted by substrate

for designated time. The cooling rate is measured to be 3–

10 K/s depending on the wetting temperature and wetting time.

By using SEM, the contact angle between the drop and

substrate, the height and the diameter of pedestal of the

metallic drop were measured. The contact angle is calculated

by the angle of the tangent line of the melt drop relative to the

substrate. The surfacial composition of the samples and

substrate was analyzed by electronic probe microscopic

analyzer (EPMA).

Fig. 2. Time dependence of contact angles of Zr47Ti13Cu11Ni10Be16Nb3 melt

on tungsten substrate at different temperature.

Fig. 1. Contact angles of Zr47Ti13Cu11Ni10Be16Nb3 melt on tungsten substrate

at (a) 1023 (b) 1123 (c) 1223 and (d) 1323 K, after melted for 2 min.

3. Experimental results and discussion

3.1. Contact angle and surface tension

Fig. 1 shows the drop morphologies obtained under the

temperature of 1023, 1123, 1223 and 1323 K after held for

2 min. It is easily seen that processing temperature has obvious

effect on the shape of melt drop. With increasing the processing

temperature, the initial angle deceases obviously. The initial

contact angle is 69.428 when heated to 1023 K. As the

temperature is increased to 1223 K, this angle is only 31.278.

The height of drops is also reduced as the contact angle

decreases.

Processing time dependence of contact angle measured at

1123, 1223 and 1323 K based on the SEM image is shown in

Fig. 2. By using the exponential equation, yZy0CAeKðxKx0Þ=t,

to fitting the experimental results, we found the contact angle

curves tested under 1223 and 1323 K fit exponential rule very

well. However, the curve tested under 1123 K is not well

consistent with exponential rule. The spreading course may be

classified into three stages when processed at 1123 K. That is

(1) the incubation period in which the spreading velocity is

relatively low; (2) the steady decrease period in which the

contact angle obviously decrease with the extension of

processing time, and (3) energetic equilibrium period in

which the contact angle gradually reach stable state resulted

from the constraint of energetic equilibrium on the surface. As

for the samples processed at 1223 and 1323 K, the incubation

period disappears, only the last two stages may be observed. It

is found that the higher the processing temperature, the shorter

the third stage. When processed at 1323 K, the equilibrium

state may be attained in about 10 min.

It was proved that the equilibrium wetting angles of

Zr55Al10Ni5Cu30 are larger than 158 when tested under the

temperature range from 1153 to 1223 K. Schroers’s exper-

imental result shows that the equilibrium wetting angles of vit 1

are smaller than 58. In this work, we measured the minimum

contact angle as low as about 68. When just considering the

contact angle it may be concluded that the vit 1 and

Zr47Ti13Cu11Ni10Be16Nb3 are more suitable to be metallic

matrix of the composite than Zr55Al10Ni5Cu30.

Fig. 3 shows the SEM images of the samples processed at

1223 K for different time. It is found that, during the wetting

Table 1

Composition in the diffusion band formed at the fringe of drops

Temperature (K) Ti Ni Cu Zr Nb W

1123 16.36 17.34 16.23 39.41 4.96 5.70

1223 21.06 14.25 13.12 34.17 4.01 13.39

1323 23.41 20.83 17.45 33.69 4.62

Fig. 3. SEM images of the samples processed at the temperature of 1223 K for

(a) 2 min, (b) 20 and (c) 25, which show diffusion bands at the fringe of drops.

X. Hui et al. / Intermetallics 14 (2006) 931–935 933

process of Zr based metallic melt on the tungsten substrate,

diffusion band is formed at the fringe of the drop. Narrow

diffusion band appears when processed for relatively short

term. After processed for 25 min, the diffusion band reaches

the scale of millimeter. The compositions of the diffusion band

analyzed by EPMA are listed in Table 1. It is shown that,

except for Zr, the concentrations of all the other constituents

are higher than the nominal composition of the matrix alloy. In

the diffusion band, there exists tungsten, which means

interdiffusion between melt and substrate takes place. When

a liquid alloy spreads on a metal substrate, interdiffusion may

result in partial dissolution of the substrate and/or the formation

of intermetallic phases. According to the reactive wetting

mechanism, it is easily to understand why vit 1 and

Zr47Ti13Cu11Ni10Be16Nb3 have better wetting ability than

Zr55Al10Ni5Cu30. When one checks the phase diagram [10],

it is known that both Nb and Ti can form limitless solid solute

with the tungsten. Therefore the tungsten tends to diffuse into

the melt drop when held under certain temperature and no

intermetallic compound is formed. At this stage, perfect

wetting of the melt on tungsten may be achieved and the

energetic equilibrium constraint among the matrix alloy, the

net substrate and atmosphere is not conserved. The decrease of

free energy associated with the partial dissolution even exceeds

the surface energy. In utmost case, the contact angle may attain

zero as has been found in some experiments [11].

Sessile drop method provides a fine pathway to determine

the surface tension of metallic melt by the equation [12]

slg ZrlgH

2

2

1:641ðdm=2Þ

1:641ðdm=2ÞCH

� �(1)

where rl is the density of matrix alloy, g gravitational

acceleration, H the height of the drop at the processing

temperature and dm the diameter of the pedestal of metallic

drop. Fig. 4 illustrates the surface tension as function of

temperature and holding time. It is shown that with the increase

of the testing temperature and the holding time the surface

tension decreases continuously. From Fig. 4(a), it is seen that

the decrease of the surface tension with increasing temperature

reflects the increase of high energetic state at high temperature.

However, as for Fig. 4(b), we consider that it may be caused by

the diffusion of tungsten into the melt drop.

4. Infiltration velocity

For a system in which the melt partly wets the fibers, the

extra pressure, Pc, needed to put metallic melt to infiltrate into

fiber perform is expressed as [13]

Pc ZK2slgVfcos q

Rfð1KVfÞ(2)

where slg is the surface tension ofmetallicmelt, qwetting contact

angle, Vf the volume fraction of fibers and Rf the radius of fiber.

For ideal unidirectional infiltration, analytical solution of

the filtration velocity can be derived as [13]

Fig. 4. Variation of surface tension with (a) temperature; and (b) time.

Fig. 5. Variation of fluid flow velocity of metallic melt with (a) the fraction of

fibers; (b) the length of fiber; and (c) infiltration pressure under 1123 K.

X. Hui et al. / Intermetallics 14 (2006) 931–935934

vZR2

8hhPCrgðH0 ChVfÞC

2slgcos q

R

� �(3)

where h is the length of fibers, H0 the height of melt. From the

above equations, one can see that the infiltration velocity, v,

may be calculated if one knows the physical property

parameters, h, q, and slg, of the melt.

Based on the present experimental data and the viscosity

of some BMGs alloys reported previously [14]. We have

obtained the velocity of fluid flow under different infiltration

conditions. Fig. 5 shows the relationship among the flowing

velocity of Zr-base metallic melt, volume fraction of fibers,

infiltration pressure and infiltration length. From Fig. 5(a), it

is seen that reducing the volume fraction and length of fibers

will increase the flow velocity of the melt. It is obvious that

the volume fraction of fibers affects the velocity intensively.

As the volume fraction is higher than 0.7, the velocity

changes smoothly. For the fiber length of 100 mm, the

velocity decrease from 1.25 to 0.001 m/s as the volume

fraction increases from 0.1 to 0.9. The increase of infiltration

pressure results in the increase of flowing velocity. Under the

same infiltration pressure, as shown in Fig. 5(b), the flow

velocity decreases according to the hyperbolic rule with the

increase of fiber length. When the fiber length is longer than

45 mm, the flow velocity varies in the range from 0.04 to

0.02 m/s. The relationship between the flow velocity and the

infiltration pressure, as shown in Fig. 5(c), may be

approximately linear. The deviation from the linear rule for

the flow velocity increases with the increasing the volume

fraction of tungsten fiber. Base on the theoretical predication

of the infiltrate velocity, we successfully prepared Zr47Ti13-Cu11Ni10Be16Nb3 BMG matrix composite reinforced by

tungsten fibers, which exhibits the compress strength and

plastic strain as high as 2415 MPa and 13%, respectively.

This result will be reported elsewhere.

X. Hui et al. / Intermetallics 14 (2006) 931–935 935

5. Summary

(1) The minimum contact angle is measured to be about 68 at

the temperature range from 1023 to 1323 K and for different

processed time, which is near that of vit 1 alloy reported

previously. The surface tension decreases with increasing

the process temperature and holding time. The diffusion

band with similar composition to that of matrix alloy is

formed at the fringe of drop, which confirms that thewetting

between the melt and tungsten belongs to reactive wetting.

(2) The relationships among the flowing velocity and proces-

sing parameters such as pressure, volume fraction of

tungsten fibers and the filtration length are established.

This infiltration dynamics investigation is believed to

provide valid foundation for the controlling preparation

conditions of fiber reinforced BMGs matrix composite.

Acknowledgements

We would like to acknowledge the financial support of

NSFC under the grant no. 50431030, 59871025, 50171006 and

the project of 973 under the grant no. G2000 67201-3.

References

[1] Clausen B, Lee SY, Ustuundag EU, Aydiner CC, Conner RD,

Bourke MAM. Scripta Mater 2003;49:123.

[2] Dragoi D, Ustuundag EU, Clausen B, Bourke MAM. Scripta Mater 2001;

45:245.

[3] Conner RD, Danliker RB, Johnson WL. Acta Mater 1998;46:

6089.

[4] Kim CP, Busch R, Masuhr A, Choi-Yim H, Johnson WL. Appl Phys Lett

2001;79:1456.

[5] Choi-Yim H, Conner RD, Szuecs F, Johnson WL. Acta Mater 2002;50:

2737.

[6] Choi-Yim H, Busch R, Koster U, JohnsonWL. Acta Mater 1999;47:2455.

[7] Conner RD, Danliker RB, Scruggs V, Johnson WL. Int J Impact Eng

2000;24:435.

[8] Choi-Yim H, Conner RD, Szuecs F, Johnson WL. Scripta Mater 2001;45:

1039.

[9] Schroers J, Samwer K, Szuecs F, Johnson WL. J Mater Res 2000;

15:1617.

[10] Baker H, et al. Alloy phase diagrams. Materials Park, OH: ASM

International; 1992.

[11] Warren JA, Boettinger WJ, Roosen AR. Acta Mater 1998;46:3247.

[12] Yu ER. J Compos (in Chinese) 1995;12:16.

[13] Murr LE. Interfacial phenomena in metals and alloys. Reading, MA:

Addison-Wesley; 1975. p. 92.

[14] Bush R, Bakke E, Johnson WL. Acta Mater 1998;46:4725.