• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.848-849
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• 2006

Bulk metallic glass (BMG) composites combining a $Cu_{54}Ni_6Zr_{22}Ti_{18}$ matrix with brass powders or $Zr_{62}A_{l8}Ni_{13}Cu_{17}$ metallic glass powders were fabricated by spark plasma sintering. The brass powders and Zr-based metallic glass powders added for the enhancement of plasticity are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation. The BMG composites show macroscopic plasticity after yielding, and the plastic strain increased to around 2% without a decrease in strength for the composite material containing 20 vol% Zr-based amorphous powders. The proper combination of strength and plasticity in the BMG composites was obtained by introducing a second phase in the metallic glass matrix.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1145-1150
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• 2003

Zr-based bulk metallic glasses have a significant mechanical properties such as high strength and elastic strain limit, and a good processing ability due to the deformation behavior such as superplasticity under supercooled liquid region. Recently, many researches on the determination of optimum working condition in various bulk metallic glasses have been carried out. In this study, the deformation behavior and forming conditions of $Zr_{55}Cu_{30}Al_{10}Ni_{5}$ bulk metallic glass were investigated under three different strain rates and at various temperatures between 627K and 727K. The glass transition temperature, crystallization temperature and supercooled liquid region of $Zr_{55}Cu_{30}Al_{10}Ni_{5}$ bulk metallic glass are 680K, 762K and 82K, respectively.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.342-347
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• 2004

The deformation behavior of a $Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass under tensile loading at different range of strain rates and temperatures between 680 K and 740 K were investigated. The variation in the deformation behavior of $Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass which resulted from the crystallization induced during testing was reported. The$Zr_{55}Al_{10}Ni_5Cu_{30}$ bulk metallic glass has showed either homogeneous or inhomogeneous deformation depending on test condition. It exhibited a maximum elongation of about 560 % at the condition of $407^{\circ}C{\times}\;10^{-4}/s$. The flow behavior exhibited three different types and the flow stress became lower at higher temperatures and lower strain rates. The increase of the time elapsed during heating resulted in the partial crystallization of bulk metallic glass phase and eventually strain hardening and brittle fracture.

• Journal of Powder Materials
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• v.14 no.6
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• pp.405-409
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• 2007

The Cu-based bulk metallic glass (BMG) composites containing Zr-based metallic glass phase have been consolidated by spark plasma sintering using the mixture of Cu-based and Zr-based metallic glass powders in their overlapped supercooled liquid region. The Zr-based metallic glass phases are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation process. The successful consolidation of BMG composites with dual amorphous phases was corresponding to the sound viscous flow of the two kinds of metallic glass powders in their overlapped supercooled liquid region.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.193-200
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• 2007

Micro forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). Al5083 superplastic alloy with very small grains has a great advantage in achieving micro deformation under low stress due to its relatively low strength at a specific high temperature range. Micro forming of $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk Metallic glass(BMG) as a candidate material for this developing process are feasible at a relatively low stress in the supercooled liquid state without any crystallization during hot deformation. In this study, the micro formability of Al5083 superplastic alloy and bulk metallic glass, $Zr_{62}Cu_{17}Ni_{13}Al_8$, was investigated with the specially designed micro vibration forming system using pyramid-shape, V-shape and U-shape micro die pattern. With these dies, micro vibration forming was conducted by varying the applied load, time. Micro formability was estimated by comparing the hight of formed shape using non-contact surface profiler system. The vibration load effect to metal flow in the micro die and improve the micro formability of Al5083 superplastic alloy and $Zr_{62}Cu_{17}Ni_{13}Al_8$ bulk Metallic glass(BMG).

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.42-47
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• 2004

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications including impact. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation on a Zr-based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact loading. These results were compared with those of spherical indentation under quasi-static and impact loading. The interface bonded specimens were adopted to observe the appearances of subsurface damage induced during indentation under different loading conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.199-202
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• 2008

In this study, we investigated the thermal properties of $Zr_{66.4}Nb_{6.4}Cu_{10.5}Ni_{8.7}Al_{8.0}$ by using a differential scanning calorimeter (DSC), and then analyzed the composition of dendrite phase by using X-ray diffraction (XRD). A series of uniaxial compression tests has been performed under the strain rates between $10^{-5}/s$ and $10^{-2}/s$ at room temperature and near SLR. This BMGC has higher high temperature strength than other Zr-based monolithic BMGs because in-situ formed crystalline phases hinder a feasible viscous flow of amorphous matrix. Warm formability is also estimated by laboratory-scale extrusion test within supercooled liquid region. It was found that BMGC has poor formability compared with nother Zr-based bulk metallic glass composite presumably due to large volume fraction of 'brittle' crystalline phases distributed within amorphous matrix.

• Journal of Powder Materials
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• v.14 no.3 s.62
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• pp.197-201
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• 2007

Bulk metallic glass (BMG) composite was fabricated by consolidation of milled metallic glass composite powders. The metallic glass composite powder was synthesized by a controlled milling process using the Cu-based metallic glass powder blended with 30 vol% Zr-based metallic glass powders. The milled composite powders showed a layered structure with three metallic phases, which is formed as a result of mechanical milling. By spark plasma sintering of milled metallic glass powders in the supercooled liquid region, a fully dense BMG composite was successfully synthesized.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.173-176
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• 2002

Viscoplastic deformation and sheet forming behavior of multicomponent Zr-based bulk metallic glass alloy has been investigated. From a series of mechanical test results, basic processing maps based on Dynamic Materials Model have been constructed to establish feasible forming conditions. Stamping in laboratory scale was then performed at the various stroke speeds and temperatures using a hydraulic press. Failure in macroscopic level was examined to check the validity of constructed processing maps.

• Journal of Powder Materials
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• v.20 no.1
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• pp.33-36
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• 2013

A bulk metallic glass-forming alloy, $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ metallic glass powders was used for good commercial availability and good formability in supercooled liquid region. In this study, the Ni-based metallic glass was synthesized using by high pressure gas atomized metallic glass powders. In order to create a bulk metallic glass sample, the $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ metallic glass powders with ball-milled Ni-based amorphous powder with 40%vol brass powder and Cu powder for 20 hours. The composite specimens were prepared by Spark Plasma Sintering for the precursor. The SPS was performed at supercooled liquid region of Ni-based metallic glass. The amorphous structure of the final sample was characterized by SEM, X-ray diffraction and DSC analysis.