Materials Science Forum
Vol. 554
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Materials Science Forum
Vol. 553
Vol. 553
Materials Science Forum
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Materials Science Forum
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Materials Science Forum
Vols. 539-543
Vols. 539-543
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Vols. 532-533
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Vols. 527-529
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Materials Science Forum
Vol. 526
Vol. 526
Materials Science Forum Vols. 539-543
Paper Title Page
Abstract: New bulk metallic glasses (BMG) have been synthesized in the Mg-Cu-RE systems
(RE= Y, Gd) with high critical diameter. In order to determine the glass forming range of these
ternary systems, the calculation of the onset of driving forces (ODF) has been performed and has
shown a large composition range for BMG formation. The synthesis of particular compositions in
this domain has shown that all the produced alloys present a high glass forming ability (GFA)
measured by DSC experiments. The ODF model, synthesized alloys by mould casting,
characterization by X-ray diffraction and DSC techniques are presented.
2018
Abstract: Bulk metallic glass (BMG) composites with dual amorphous phases were fabricated by
spark plasma sintering of a mixture of Cu-based and Zr-based amorphous powders in their
overlapped supercooled liquid region. The Zr-based amorphous phases are well distributed
homogeneously in the Cu-based metallic glass matrix after consolidation. The BMG composite still
remains as an amorphous structure after consolidation. The BMG composite with dual amorphous
phases shows macroscopic plasticity after yielding, and the plastic strain increased to around 3.4%
in the BMG composite containing 30 vol% Zr-based amorphous phase. The successful
consolidation of BMG composite with enhanced plasticity was achieved by introducing a second
amorphous phase in the metallic glass matrix.
2026
Abstract: Formation of the icosahedral order in supercooled liquids and glassy phases is
investigated for a model alloy system by using molecular dynamics simulations. The simulation
results show that the short-range icosahedral order grows in the supercooled liquids as well as in
the glassy phases. Structural analyses reveal that the icosahedral clusters form a network in which
the clusters are connected via the pentagonal-bicap sharing. Geometrical property of the network
formed by the icosahedral clusters is an origin of medium-range order in the glassy phases
2031
Abstract: The effect of partial crystallization on the mechanical properties of a Zr based bulk
metallic glass (Vitreloy 1) is investigated. Viscoelastic properties are studied by mechanical
spectroscopy in large frequency and temperature ranges, both below or above the glass transition
temperature (Tg), whereas viscoplastic properties are investigated by compression tests . To study
the interaction between crystallization and mechanical properties at high temperature,
nanocomposites are produced thanks to appropriate heat treatments. Formation of nanocrystalline
particles induces an increase of the storage elastic modulus, especially in the glass transition range,
where this modulus is very low in the amorphous material. It also results in a decrease of the loss
elastic modulus, corresponding to a decrease of the atomic mobility. Finally, partial crystallization
induces very large hardening revealed by the compression tests but the hardening extent depends
strongly on the applied strain rate.
2036
Abstract: The atomistic structure of Czochralski-grown SixGe1-x binary mixed semiconductor was
studied experimentally and theoretically. By extended X-ray absorption fine structure (XAFS)
studies it was found that bulk SiGe semiconductor is a random mixture and that the Ge-Ge, Ge-Si
and Si-Si bond lengths maintain distinctly different lengths and vary in a linear fashion against the
alloy composition across the whole composition range 0 < x < 1, in good agreement with
expectations derived from the ab-inito electronic structure calculations. The result indicates that
SiGe is a suitable model for a disorder mixed material and that the bond lengths and bond angles are
distorted with the composition.
2043
Abstract: The electronic structure and phase stability of the Zr-Ni-Al ternary glassy alloys, have
been systematically investigated experimentally and theoretically. Thermal stability and
crystallization process have been clarified by the DSC and XRD measurements. Composition
dependence of the stability parameter; Tg/Tl has been clarified. The electronic structure around the
Fermi level has been investigated by using the high resolution UPS. It is found that there is a
sizable pseudogap at the Fermi level of the electronic structure of the Zr65Ni20Al15 glassy alloy.
The DVXα calculations for the charateristic clusters in the Zr-Ni-Al glassy alloy having high glass
forming ability have been also performed. It is found that these clusters formation reduces the
internal energy and can contribute to the phase stability. The LMTO-ASA band calculations for
the Zr6NiAl2 compound which is the most relevant compound to the Zr60Ni25Al15 glassy alloy have
been also performed. It is found that there is a sizable pseudogap at the Fermi level in its
electronic structure, suggesting exiting of the pseudogap of the glassy alloy.
2048
Abstract: Monolithic Zr65Al7.5Ni10Pd17.5 and Zr65Al7.5Ni10Cu17.5 hardly had plastic deformability in
tension at room temperature, although Zr65Al7.5Ni10Pd17.5 showed a large plastic strain in
compression. A depressed zone that is the evidence of viscous flow deformation (so-called viscous
flow depression zone; VFD-zone) was observed for Zr65Al7.5Ni10Pd17.5 around the edge at the point
of failure on its specimen surfaces. However, no VFD-zone was seen for Zr65Al7.5Ni10Cu17.5. Thus,
a clear difference in tensile plastic behavior was found between Zr65Al7.5Ni10Pd17.5 and
Zr65Al7.5Ni10Cu17.5. A structural change in the vicinity of the fracture surface of Zr65Al7.5Ni10Pd17.5
was measured by micro-beam X-ray diffractometry (MB-XRD). We may be able to discuss the
room temperature plasticity of Zr65Al7.5Ni10Cu17.5-xPdx bulk metallic glasses correlating with the
phase stability of the amorphous and icosahedral quasi-crystalline phases.
2054
Abstract: The free volume relaxation just under the glass transition region was investigated by the
high-resolution density measurement using the bulk metallic glasses with the compositions of
Pd40Ni40P20 and Zr55Cu30Ni5Al10. The relaxation process was well described by a stretched
exponential function with Kohlrausch exponent values less than unity. The reduced free volumes in
an as-quenched state were estimated as 0.0117 and 0.0353 for Pd40Ni40P20 glass and Zr55Cu30Ni5Al10
glass, respectively. The specific heat curves Cp(T) for Pd42.5Cu30Ni7.5P20 alloy were obtained for the
supercooled liquid, the equilibrium liquid and the crystallized alloy. The isenthalpic Kauzmann
temperature TKH and isentropic Kauzmann temperature TKS were estimated as 471 K and 522 K,
respectively, from the specific heat data.
2059
Abstract: Viscosity of a Zr55Cu30Al10Ni5 supercooled liquid alloy having bulk metallic glass
forming ability has been measured by using a penetration viscometer with a cylindrical probe
under high speed heating conditions at rates between 20°C/min and 400°C/min in the temperature
range from the glass transition temperatures (Tg) up to above the crystallization temperatures
(Tx). The viscosity of the alloy decreased with increasing the heating rate and tended to saturate at
the heating rate of 200°C/min and above. Corresponding measurements of the differential thermal
calorimetry (DSC) under the high-speed heating conditions have been also done.
2071