Journal of Minerals & Materials Characterization & Engineering, Vol. 3, No.2, pp 91-98, 2004 Printed in the USA. All rights reserved
Melt Infi ltration Casting Of Zr57Al10Nb5Cu15.4Ni12.6
Amorphous Matrix Composite
K.Q. Qiu and Y.L. Ren
School of Materials Science and Engineering, Shenyang University of Technology,
58 South Xinghua Street, Shenyang 110023, China.
Tel.: 86-24-25691315; Fax: 86-24-25694028
The Zr57Al10Nb5Cu15.4Ni12.6 bulk metallic glass-forming alloy is reinforced with
tungsten fiber. Cylindrical samples up to 6.3 mm in diameter and 7cm in length have been
synthesized using melt infiltration casting method. The structure and microstructure of
the composites processed in typical conditions were analyzed by x-ray diffraction and
scanning electron microscopy. The suitable interface reaction and fully amorphous
matrix can only be obtained through the combination of a suitable infiltration
temperature and time. The processing conditions were more rigorous compared to those
of making Zr-Ti-Ni-Cu-Be matrix composite due to intermetallic compound nucleation
when exposed to the tungsten fibers. A technique map, including infiltrating temperature
and time is presented in this paper.
Keywords: melt infiltration casting composite bulk metallic glass
1. Introduction
The high glass-forming ability and high thermal stability against cr ystallization of
recentl y developed glassy alloys [1-3] allow their use for fundamental investigations and
practical applications. The development of bulk metallic glass matrix composites
especiall y opens new opportunities for application of metallic glass. The multicomponent
Zr57Al10Nb5Cu15.4Ni12.6 (Vit106) is known to be one of the best glass-formers with a
critical cooling rate of ~10Ks-1[4]. Such a glassy alloy has promising properties such as
high yield strength and high elastic strain limit combined with relatively high fracture
toughness, fatigue, and corrosion resistance [5,6]. However, it has almost no ductility in
tension or compression. The lack of ductility could be a serious drawback in many
applications. Thus, one of the motivations for adding second phase particles or
continuous metal fibers to the metallic glass is to hinder propagation of shear bands and
encourage the formation of multiple shear bands, which can increase plastic deformation
of bulk metallic glasses. Many researchers [7-10] have focused on the processing of fiber
or particulate reinforced composites with a metallic glass matrix to improve the
mechanical properties. It was reported that bulk metallic glass Zr-Ti-Ni-Cu-Be [7] and
Zr-Nb-Al-Ni-Cu [8] alloys reinforced with a ductile metal (W, Ta or steel) fiber or
ceramics (SiC, WC, or TiC) have improved their mechanical properties. The Inoue group
has successfully synthesized ZrC particle reinforced Zr55Al10Ni5Cu30 composites by in-
situ reaction [11] or by adding SiC particle to Cu47Ti34Zr11Ni 8 metallic glass [12]. In this
92 K.Q.Qiu and Y.L.RenVol. 3, No.2
paper, the techniques for melt infiltration casting of Zr57Al10Nb5Cu15.4Ni12.6 alloy and the
influence of interface reaction on fabrication of the composites are investigated.
When the second reinforced medium is dispersed in the glassy matrix, there is a
high risk of partial crystallization at the interface between the glassy matrix and
reinforcing phase. The important factors in preparation of above-mentioned composite
materials, one can list a high glass-forming ability of the glassy matrix, low reactivity,
small difference in thermal expansion coefficient and good wettability between
reinforcement and matrix. If these factors are achieved and the second reinforcing phase
is homogeneously dispersed without agglomeration or segregation in the glassy matrix,
the reinforcement is likely to suppress the propagation of shear bands and might increase
the toughness and fatigue resistance of the composi te materi als. Long fibe r reinfo rcement
homogeneously distributed in the glassy matrix is a good method for that purpose.
Tungsten fiber is used as reinforcement not only because it has limited reactivit y
with the matrix material due to its high melting temperature but also the composite is a
candidate material used as W-base kinetic energy penetrators due to its high density and
self-sharpening behavior during dynamic deformation. In addition, the matrix alloy is a
beryllium-free Zr-based glass former, which has no harmful to health.
2. Experimental
In this study the Zr57Al10Nb5Cu15.4 Ni 12.6 alloy was selected as the matrix material.
The master alloy was prepared by alloying together the constitutive elements in an arc
furnace under a titanium-gettered argon atmosphere. The starting materials were high-
purity (99.8% metals basis or better) research grade metals. The oxygen content of the
starting material was in the range of 30~35ppm in weight percent.
Tungsten fiber with a nominal diameter of 250 µm was used as t he reinforcement
in the composite. The apparatus and methods used for the composite specimen
fabrication are almost the same as the one described in the literature [7]. The
reinforcement material was placed in the sealed end of a 6.3mm inner diameter quartz
tube which was evacu ated to a pressure o f no more than 1×10-3 Pa. Then the sample tube
was heated in a vertical resistive tube furnace with a temperature feedback controller.
Two heating stages were used in the melt infiltration processing. One was the initial
heating stage held at 1330±20°K, well above the liquidus temperature (1100°K) of the
glass-forming alloy. The liquidus temperature was measured by the instrument of
NETZSCH DSC 404°C at a heating rate of 20K/min. The sample was held at the initial
heating temperature for 12 min. The temperature was then lowered to the second stage
held at different temperature from 1150 to 1300°K according to preset value. When the
furnace reach ed the preset temperature, a positive pressure of 260kPa purified argon was
applied above the melt and held for different time ranging from 5~20min to allow
infiltration of the molten matrix material into the reinforcement. Then the sample was
quickly quenched in a supersaturated NaCl/H2O solution.
Vol. 3, No.2 Melt Infiltration Casting of Zr57Al10Nb5Cu15.4Ni12.6 Amorphous Matrix Composite93
The specimens were first ground to a 6mm diameter and then sliced normal to the
fiber orientation. X-ray diffraction patterns of the slices were obtained using a RIGAKU
D/max-rA diffractometer and Cu Kα radiation. The fiber/matrix interface in selected
samples was examined by EPM-810Q scanning electron microscopy with electron
In this paper, we generally fabricated 6.3mm diameter samples with nominal
reinforcement volume fractions of 20~30%, because the samples with higher volume
fraction of wires the XRD patterns of the matrix pattern is obscured due to the large
intensity difference between the Bragg peaks of
the reinforcement and the broad amorphous
bands. The nominal volume fraction of tungsten
fiber is determined by overall cross-area of fibers
divided by the internal cross-area of the quartz
tube. Whether the fiber distribution is even or not
does not affect the questions we concern.
3. Results
3.1 Temperature dependence of interface
Fig.1 shows SEM micrographs of
interfacial region of the composite. The samples
were held for 10min at temperature of 1150°K,
1225°K and 1300°K, respectively. The white part
in each picture is tungsten fiber while the black
one the matrix. At lower temperature of 1150°K,
no interfacial reaction is seen as shown in Fig. 1
(a). Increasing the temperature to 1225°K, a
reaction layer was formed around the tungsten
wires and some white particles were eroded away
from the wires. When the temperature was
increased to 1300°K, the reaction layer becomes
thicker and more particles eroded away from the
Fig. 2 shows typical x-ray diffraction
patterns of two cross-sectioned composite samples
with tungsten volume fraction of 25% as shown in
Fig.1. For comparison, the pattern from an
unreinforced sample produced at 1225°K is also
included. The unreinforced matrix pattern shows
broad diffraction peaks typical of a fully
amorphous structure (Fig.1(a)). The same broad
Figure 1. SEM micrograph of W fiber/
Zr57Al10Nb5Cu 15. 4Ni12. 6 composites
processed at temperature of (a) 1150K,
(b) 1225K and (c) 1300K, respectively,
for the same in filtration time period of
10min. Lighter regions are W wires.
Darker regions are matrix. Gray regions
are interfacial reaction layers
94 K.Q.Qiu and Y.L.RenVol. 3, No.2
peaks are also visible in the pattern
processed at temperature of 1225°K as
shown in Fig.2(b). The difference is that
the higher intensity of W diffraction peaks
superimpose on them, but the intensity of
amorphous peak is reduced for the one
processed at high infiltration temperature
of 1300°K as shown in Fig.2(c). This
indicated that the quantity of the
amorphous phase in the matrix is reduced
even though we do not obviously observe
the diffraction peaks of crystalline phases
due to the high intensity of W phase or the
quantity of crystalline phases is not high
enough to show them. But we do observe
some crystalline phases formed as
indicated by a vertical arrow as shown in
Fig1(c). The sample processed at 1150°K gives almost the same patterns as shown in
From the line scans (Fig. 1c) the amount of tungsten in the reaction layer
decreased and the zirconium increased compared with original composition. At
temperature of 1300°K, the average amount of zirconium measured by electron
microprobe in the white particles (marked with a declining arrow as shown in Fig. 1(c))
was 28.3at. %. The W content reduced to 54.70 at. %. The balance is Al (2.1 at. %), Cu
(7.4 at. %), Ni (4.3 at. %) and Nb (3.2 at. %). This result constitutes the W-based alloy
that is im possible t o be a glass form e r. The dissolved W did not precipitate as nearl y pure
bcc W on cooling as in the case of Be-b earing alloy [13]. T he relativel y high Nb content
in the eroded particles gives us an idea that it is easy to be disturbed into W based alloy.
Away from the interface region or the eroded particle, the composition for the oth er parts
(the black part) in the matrix was not changed significantly. Therefore not much more
other crystalline phases observed on the XRD pattern as shown in Fig2(c).
3.2 Time dependence of infiltration
The influence of the infiltration time at
1225°K was also studied. Fig.3 shows a sample
that was held for 20 min at 1225°K. An
interface reaction occurred just as the sample
processed at temperature of 1300°K for 10 min.
There is a little difference from W reinforced
Zr55Al10Ni5Cu30 metallic glass matrix
composites in which time is very important in
controlling eroding and wetting process [14].
Here the time and temperature may play a
similar role in controlling such a process.
20 3040 50 6070 80
2θ; deg.
: W
Cu Kα
Figure 2. X-ray diffraction patterns for cross-
sectioned sa mples of unreinforced bulk metallic
glass (a) and tungsten reinforced bulk metallic
glass matrix composites processed at temperature
of 1225K (b) and 1300K(c) respectively
Figure 3. SEM micrograph of metal
matrix composite processed at
temperature of 1225K for 20min
Vol. 3, No.2 Melt Infiltration Casting of Zr57Al10Nb5Cu15.4Ni12.6 Amorphous Matrix Composite95
3.3 Technique map for melt infiltration
A batch of samples was made at
different infiltrating temperature and time.
Apart from the reinforcement, the overall
crystallites in the matrix should not be
above 5 vol.%, we consider this value as
an upper threshold value for determining
appropriate infiltrating temperature and
time, above which interface reaction will
cause intermetallic compounds formation
just as the vertical arrow indicated in
Fig.1(c). When the fibers are separated
from the matrix of the sample during
tension or not wetted completely by liquid
metal [15], we consider the infiltrating
temperature or time of this case as a lower
threshold value, below which the binding between fibers and matrix is weak. Fig.4 shows
the results of the experiments. A suitable reaction area was formed between the low
wetting area and the over reaction area. It becomes narrow at higher temperatures and
less time and wider at lower temperatures and over a longer time span. When the
infiltrating temperature is below 1150°K, however, it is difficult to ensure melting to
infiltrate the fibers, especially when the volume fraction of fiber is over 40%. This
indicates that there is not enough flowing ability or infiltrating ability for the melt at such
conditions. Therefore the lowest temperature and longest time for melt infiltrating are
1150°K and 20min, respectively. The narrowest superheating region of melt infiltration
temperature is about 50°K.
4. Discussions
To take advantage of the mechanical properties of the metallic glass in the
composite, it is important to avoid crystallization of brittle intermetallics [13]. In fact, an
interfmetallic such Zr2Cu is formed in the matrix as the vertical arrow indicated in the
Fig.1(c) when interface reaction occurred. This intermetallic bar is normal to the
interface. Therefore it is important to avoid interface reaction during processing.
During the initial stage of processing, prior to infiltration, the alloy was preheated
to a certain temperature required to remelt some residual crystalline particles present in
the starting ingots. It was found that some inclusions were included and crystalline phases
were formed in the matrix without such a sta ge. Dandliker [ 7] and Lin [16] found in other
Zr-based bulk glass-formers that preheating a few hundred degrees above the melting
temperature was necessary to achieve a larger undercooling for the melt. Preheating can
cause the nucleation sites to be inactive and that nucleation is impossible for some
Figure 4. Melt infiltratio n map for
Zr57Al10Nb5Cu 15. 4Ni12. 6 bu lk metallic glass matrix
96 K.Q.Qiu and Y.L.RenVol. 3, No.2
impurities present in the melt.
In Be-bearing bulk metallic glass composite, it was reported [13] that the atom of
tungsten diffuses out from the wires over a rel atively narrow z one owing to an apparentl y
very low diffusion constant. In a several micron thick layer near the glass/W-wire
interface, the matrix is found to contain about 12 at. % W after being processed. This W
precipitates as nearly pure bcc W on cooling and also forming a dispersion of W
nanocrystals in the glass matrix. The glass forming ability of the matrix is otherwise
unaffected. Those results are a little different from the case of what we know about
Zr57Al10Nb5Cu15.4Ni12.6 metallic glass matrix composite. Considering that the W content
in the reaction layer is decreased with the processing temperature increasing, we can
therefore infe r that the element s, such as Zr, Al, Cu, Ni and Nb, diffuse into the tungsten
wires forming thick layers due to their relatively high diffusion constants during W
diffusing out of tungsten wires. The reaction layers or penetrated layers were W-based
layers. When the W in the reaction layers reduced to a certain amount, the strength of
grain boundaries of tungsten is too low to sustain its grains under thermal destruction.
The grains were ver y much eroded away from the fibers forming W-rich particles which
were shifted away from fibers with increasing processing time and temperature. The
quantity of Zr and other elements in reaction layers were increased with temperature,
therefore, the matrix composition, especially the composition in the reaction layers, was
beyond the composition of glass former or the interf aces between the matrix and re action
layers stimulated the formation of some crystalline nuclei, which grow directly into the
matrix formed vertical arrays of intermetallic bars.
5. Conclusions
Bulk Zr57Al10Nb5Cu15.4Ni12.6 metallic-glass matrix-composite up to 6.3mm in
diameter and 7cm in length can successfully be fabricated by melt infiltration of the
reinforcement of tungsten fibers. The suitable interface reaction and fully amorphous
matrix can only be obtained through the combination of the suitable infiltration
temperature and time. A technique map for p rocessing condition relating temperature and
time is presented. The lowest temperature and longest time for melt infiltrating are
1150°K and 20min, respectively. The narrowest superheating region of melt infiltration
temperature is about 50°K.
Acknow l ed gments
The financial support from the Shenyang University of Technology is greatly
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