• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.368-368
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• 2009

• 한국주조공학회지
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• 제30권5호
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• pp.167-173
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• 2010

벌크 비정질 합금의 특성상 점도가 높고, 냉각속도가 빨라 냉각되는 합금의 온도를 직접 측정하는 것은 곤란하므로, 측정에 의하여 냉각속도를 구하는 것은 매우 어렵다. 본 연구에서는 합금의 온도를 직접 측정하는 대신 금형의 온도를 측정하고, 측정된 금형의 온도를 상용 열해석 프로그램을 이용한3차원 계산 결과와 비교, 보정하는 역문제 기법을 사용하여 Cu계와 Zr계 벌크 비정질합금의 냉각속도를 예측하였다. 예측된 냉각속도는 금형온도와 시편의 두께에 따라Cu계의 경우는 284~300 K/s, Zr계는 279~289 K/s로, 초기 금형온도의 영향은 크지 않은 것으로 나타났다. 전산모사 결과와 달리 금형을 수냉한 쪽보다 가열한 쪽의 응고중 냉각속도가 빨라 조직이 더 미세한 것으로 나타났는데, 이는 응고중 금형과 주물간에 에어갭의 형성으로 열전달을 방해 받은 영향으로 사료된다.

• 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.

• 한국재료학회지
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• 제19권5호
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• pp.276-280
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• 2009

The effect of the initial packing structure on the plasticity of amorphous alloys was investigated by tracing the structural evolution of the amorphous solid inside a shear band. According to the molecular dynamics simulations, the structural evolution of the amorphous solids inside the shear band was more abrupt in the alloy with a higher initial packing density. Such a difference in the structural evolution within the shear band observed from the amorphous alloys with different initial packing density is believed to cause different degrees of shear localization, providing an answer to the fundamental question of why amorphous alloys show different plasticity. We clarify the structural origin of the plasticity of bulk amorphous alloys by exploring the microstructural aspects in view of the structural disordering, disorder-induced softening, and shear localization using molecular dynamics simulations based on the recently developed MEAM (modified embedded atom method) potential.

• 한국분말재료학회지
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• 제20권1호
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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.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.258-262
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• 2008

Micro forming is a suited technology to manufacture very small metallic parts(several $mm{\sim}{\mu}m$). In this study, the micro forming property was studied, using Al5083 superplastic alloy with micro grain, suitable for the micro forming process and Zr-BMG amorphous with pseudo-superplastic phenomena in the supercooled liquid state. Micro forming experiments under stastic load status showed that distortion by slip and spin of the grain system and slip inside the grain was observed in the Al5083 superplastic alloy. In case of Zr-BMG, because there is no grain, the distribution of the forming property was similar to the load distribution between punch and metal.

• 한국주조공학회지
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• 제44권4호
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• pp.97-102
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• 2024

본 연구는 부분적으로 비정질 구조와 특성을 가진 Zr-14Cu-7.5Ni-2.6Al 광폭 리본의 특성을 Hall effect, SEM-EDX, XRD 등을 사용하여 분석하였다. 멜트 스피닝 방법으로 제작된 이 Zr-14Cu-7.5Ni-2.6Al 기반 합금 리본은 두께가 96㎛ 이하이고 폭이 100mm이다. 인장강도 l,641MPa, 항복강도 l,541MPa, 연신율 1%, 탄성계수 98GPa의 성능을 나타냈다. Bulk concentration, Resistivity, Mobility 값은 일반적인 heavy doping 세라믹과 금속의 중간값을 보이고 일반 금속보다 약 100배 정도 약하여 Si에 근접하며 전기 전도도가 좋은 편이다. 또한, 극한 온도에서의 폴딩 테스트를 수행하여 -20℃에서 150,000회, 24℃에서 300,000회, 60℃에서 150,000회를 견디며 폴딩 불량이 나타나지 않았다. 이 결과는 Zr-14Cu-7.5Ni-2.6Al 광폭리본 합금의 우수한 내구성과 신뢰성을 보여주며, 이러한 합금을 사용한 전자 제품의 개발 가능성을 시사한다.

• 한국재료학회지
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• 제19권2호
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• pp.79-84
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• 2009

A series of experiments demonstrated that an addition of Ag into $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ amorphous alloys alters the plasticity of the alloys in a systematic manner. Energy dispersive x-ray spectroscopy (EDS) conducted on the $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ alloys exhibited the presence of compositional modulation, indicating that compositional separation had occurred. The presence of compositional modulation was also validated using a combined technique of molecular dynamics and Monte Carlo simulation. In this study, the effect of Ag on the compositional separation in $(Cu_{0.5}Zr_{0.5})_{100-x}Ag_{x}$ bulk amorphous alloys was investigated to understand the role played by the phase-separating element on the plasticity of the amorphous alloys.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.680.1-680.1
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• 2006

• Applied Microscopy
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• 제45권2호
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• pp.37-43
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• 2015

In present work, work-hardening behavior of TiCu-based bulk metallic glass composite with B2 particles has been studied by systemic structural and mechanical investigations. After yield, pronounced work-hardening of the alloy was clearly exhibited, which was mainly related to the martensitic transformation as well as the deformation twinning in B2 particles during deformation. At the early plastic deformation stage (work-hardening stage), the stress-induced martensitic transformation from B2 phase to B19' phase and deformation-induced twinning of B19' phase was preferentially occurred in the around interface areas between B2 phase and amorphous matrix by stress concentration. The higher hardness value was observed in vicinity of interface within the B2 particles which are probably connected with martensitic transformation and deformation twinning. This reveals that the work-hardening phenomenon of this bulk metallic glass composite is a result of the hardening of B2 particles embedded in amorphous matrix.