• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.143-145
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• 2007

The correlation between crystallization and deformation behavior in the supercooled liquid region (SLR) of a $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ bulk metallic glass (BMG) alloy is investigated by compression tests, differential scanning calorimetry (DSC), electron energy loss spectrometry (EELS) and high resolution transmission electron microscopy (HRTEM). In the SLR, This BMG alloy was strongly depended on the deformation temperature and the alloy exhibits important change in deformation behavior after a given time which is directly connected to the development of crystallization. Compressive stress impeded decomposition and consequently retarded forming of nano-crystal, which led to enlarge the homogeneous deformation region of the BMG alloy in SLR during compression test.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.93-96
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• 2003

Recently, various bulk metallic glasses (BMG's) haying good mechanical and chemical properties were developed. BMG's can easily be deformed in the supercooled liquid region, via viscous flow mechanism. In our previous work, we evaluated the deformation behavior and some other basic properties of Z $r_{41.2}$ $Ti_{13.8}$C $u_{12.5}$N $i_{10}$B $e_{22.5}$ alloy. In this study, we investigated the micro forming of Z $r_{41.2}$ $Ti_{13.8}$C $u_{12.5}$N $i_{10}$B $e_{22.5}$ alloy. The process condition was chosen based on the viscosity data from TMA, and superalloy and Si wafer with micro patterns on the surface were used as forming die. The alloy showed good replication of the patterns. However, some stripe patterns, resembling scratches, appeared on the deformed alloy surface. These scratches can be reduced or eliminated by polishing before forming.ing.ore forming.ing.

• 한국표면공학회지
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• 제41권6호
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• pp.301-307
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• 2008

In this paper, nanocrystallization of CuNiTiZr bulk metallic glass (BMG) subjecting to a kinetic spraying, dependent on impact velocity, was investigated by numerical and experimental approaches. The crystallization fraction and nucleation activation energy of initial feedstock and as-deposited coating were estimated by DSC and Kissinger method, respectively. The results of numerical modeling and experiment showed that the crystalline fraction and nucleation activation energy in BMG coatings were depended on kinetic energy of incident particle. Upon impact, the conversion of particle kinetic energy leads to not only decreasing free energy barrier but also increasing the driving force for an amorphous to crystalline phase transformation. The nanocrystallization of BMGs is associated with the strain energy delivered by a plastic deformation with a high strain rate.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.118-121
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• 2007

Bulk metallic glass (BMG)/crystalline composites comprising a copper based BMG alloy and crystalline nickel were produced by means of eloctroless plating of nickel on $Cu_{54}Zr_{22}Ti_{18}Ni_6$ BMG powder and subsequent consolidation using spark plasma sintering. The plastic deformation behavior of BMG/crystalline composites was examined by uniaxial compression test at various temperatures in the supercooled liquid region (SLR) of the BMG alloy. The evolution of strain states during uniaxial compression was tackled by microstructure observations. Deformation temperature played an important role in the deformation behavior of BMG/crystalline composites, which was attributed to a strong temperature dependence of the flow stress of the BMG alloy in the SLR. BMG/crystalline composites deformed homogenously in the temperature range where the flow stress of the BMG alloy was close to that of crystalline nickel. In contrast, inhomogeneous deformation was observed in the temperature range where the flow stress of the BMG alloy largely differs from that of crystalline nickel.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.936-936
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• 2006

Bulk amorphous materials have been intensively studied to apply for various advanced industry fields due to their high mechanical, chemical and electrical properties. These materials have been produced by several techniques such as mechanical alloying, melt spinning and gas atomization, etc. Among them, the atomization is the most potential technique for commercialization due to high cooling rate during solidification of the melt and mass productivity. However, the amorphous powders still have some limitations because of their low ductility and toughness. Therefore, intensive efforts have to be carried out to increase the ductility and toughness. In this study, the Ni-based amorphous powder was produced by the gas atomization process. And in order to increase the ductile toughness, ductile Cu phase was coated on the Ni amorphous powder by spray drying process. The characteristics of the as-synthesis powders have been examined and briefly mentioned. The master alloy with $Ni_{57}Zr_{20}Ti_{16}Si_2Sn_3$ was prepared by vacuum induction melting furnace with graphite crucible and mold. The atomization was conducted at $1450^{\circ}C$ under the vacuum of $10^{-2}$ torr. The gas pressure during atomization was varied from 35 to 50 bars. After making the Ni amorphous powders, the spray drying was processed to produce the Cu -coated Ni amorphous composite powder. The amorphous powder and Cu nitrate solution were mixed together with a small amount of binder and then it was sprayed at temperature of $130^{\circ}C$ and rotating speed of 15,000 R.P.M.