• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.321-327
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• 2008

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_6$) coating was produced by cold spraying as a new fabrication process. The microstructure and macroscopic properties of amorphous coating layer was investigated and compared with those of cold sprayed pure Cu coating. Amorphous powders were prepared by gas atomization and Al 6061 was used as the substrate plate. X-ray diffraction results showed that Cu based amorphous powder could be successfully deposited by cold spraying without any crystallization. The Cu based amorphous coating layer ($300{\sim}400{\mu}m$ thickness) contained 4.87% porosity. The hardness of Cu based amorphous coating represented $412.8H_v$, which was correspond to 68% of the hardness of injection casted bulk amorphous material. The wear resistance of Cu based amorphous coating was found to be three times higher than that of pure Cu coating. The 3-point bending test results showed that the adhesion strength of Cu based amorphous coating layer was higher than that pure Cu coating. It was also observed that hard Cu base amorphous particle could easily deform soft substrate by particle collisions and thus generated strong adhesion between coating and substrate. However, the amorphous coating layer unexpectedly represented lower corrosion resistance than pure Cu coating, which might be resulted from the higher content of porosity in the cold sprayed amorphous coating.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.406-412
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• 2005

This work is to present a new synthesis of metallic glass (MG)/metallic glass (MG) composites using gas atomization and spark plasma sintering (SPS) processes. The MG powders of $Cu_{54}Ni_6Zr_{22}Ti_{18}$ (CuA) and $Ni_{59}Zr_{15}Ti_{13}Nb_7Si_3Sn_2Al_1$(NiA) as atomized consist of fully amorphous phases and present a different thermal behavior; $T_g$ (glass transition temperature) and $T_x$ (crystallization temperature) are 716K and 765K for the Cu base powder, but 836K and 890K for the Ni base ones, respectively. SPS process was used to consolidate the mixture of each amorphous powder, being $CuA/10\%NiA\;and\;NiA/10\%CuA$ in weight. The resultant phases were Cu crystalline dispersed NiA matrix composites as well as NiA phase dispersed CuA matrix composites, depending on the SPS temperatures. Effect of the second phases embedded in the MG matrix was discussed on the micro-structure and mechanical properties.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.304-308
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• 2002

The new Cu-Zr-Ti-Ni-Pd amorphous alloy system has been introduced and manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties of the alloys were examined. The reduced glass transition temperature(Trg = Tg/Tm) and the supercooled liquid region(${\Delta}$Tx = Tx-Tg) of $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ alloy were 0.620 and 57 K respectively. $Cu_{49}Zr_{30}Ti_{10}Ni_5Pb_6$ amorphous alloy was produced in the rod shape with 2mm diameter using the Cu-mold die casting. The hardness value of the amorphous bulk alloy was 432 DPN.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.728-733
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• 2009

Cu based amorphous ($Cu_{54}Zr_{22}Ti_{18}Ni_{6}$) powders were deposited onto Al 6061 substrates by cold spray process with different powder preheating temperatures (below glass transition temperature: $350^{\circ}C$, near glass transition temperature: $430^{\circ}C$ and near crystallization temperature: $500^{\circ}C$). The microstructure and macroscopic properties (hardness, wear and corrosion) of Cu based amorphous coating layers were also investigated. X-ray diffraction results showed that cold sprayed Cu based amorphous coating layers of $300{\sim}350{\mu}m$ thickness could be well manufactured regardless of powder preheating temperature. Porosity measurements revealed that the coating layers of $430^{\circ}C$ and $500^{\circ}C$ preheating temperature conditions had lower porosity contents (0.88%, 0.93%) than that of the $350^{\circ}C$ preheating condition (4.87%). Hardness was measured as 374.8 Hv ($350^{\circ}C$), 436.3 Hv ($430^{\circ}C$) and 455.4 Hv ($500^{\circ}C$) for the Cu based amorphous coating layers, respectively. The results of the suga test for the wear resistance property also corresponded well to the hardness results. The critical anodic current density ($i_{c}$) according to powder preheating temperature conditions of $430^{\circ}C$, $500^{\circ}C$ was lower than that of the sample preheated at $350^{\circ}C$, respectively. The higher hardness, wear and corrosion resistances of the preheating conditions of near $T_{g}$ and $T_{x}$, compared to the properties of below $T_{g}$, could be well explained by the lower porosity of coating layer.

• Journal of Korea Foundry Society
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• v.22 no.6
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• pp.288-292
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• 2002

Ni-base amorphous alloys were manufactured using melt-spinning and Cu-mold die casting methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The reduced glass transition temperature and the supercooled liquid region of $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$alloy were 0.621 and 46 K respectively. $Ni_{51} Nb_{20} Zr_9 Ti_9 Co_8 Cu_3$ alloy was produced in the rod shape 3mm diameter using the Cu-mold die casting. Hardness, compression strength, elongation and elastic modulus of the alloy were 850 DPN, 2.75 GPa, 1.8% and 150 GPa respectively. Moreover, compression strength of 2.75 GPa was the highest value in the amorphous bulk alloy produced up to now.

• Applied Microscopy
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• v.46 no.1
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• pp.32-36
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• 2016

The Cu-based bulk glassy alloys in Cu-Zr-Ti-Ni systems were prepared by means of copper mold casting. The Cu-based bulk glassy alloys samples were tested by X-ray diffractomer (XRD), differential scanning calorimeter, scanning electron microscopy (SEM), Instron testing machine and Vickers hardness instruments. The result indicated that the prepared Cu-Zr-Ti-Ni alloys were bulk glassy alloys. The temperature interval of supercooled liquid region (${\Delta}T_x$) was about 45.48 to 70.98 K for the Cu-Zr-Ti-Ni alloy. The Vickers hardness was up to 565 HV for the $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloy. The $Cu_{50}Zr_{25}Ti_{15}Ni_{10}$ bulk glassy alloys were annealed in order to obtain nanocrystals. The results showed that the Vickers hardness was raise up to 630 HV from 565 HV. As shown in XRD results, the amorphous alloys changed to nanocrystals, which were $Cu_8Zr_3$, $Cu_3Ti_2$ and CuZr, improved the hardness. The SEM analysis showed that the compression fractured morphology of amorphous alloys was brittle fracture, and the fracture morphology after annealing was ductile fracture. This proved that annealing of amorphous to nanocrystals can improve the plasticity and toughness of amorphous alloys.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.203-206
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• 2004

Copper-based bulk amorphous alloy composite was synthesized by using the copper-coated $Cu_{54}Ni_{6}Zr_{22}Ti_{18}$ amorphous powder which was obtained by argon gas atomization. The amorphous powder having a super-cooled liquid region of 53 K was coated by crystalline copper by electroless coating. The consolidation was carried out by manufacturing performs and by the subsequent warm extrusion at 743 K. During the compression test at the room temperature, the composite containing a large fraction of crystalline copper displayed a larger plastic strain after yielding. FEM simulation revealed change in fracture modes in the composites depending on the amount of crystalline copper in the composites.

• Journal of Powder Materials
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• v.16 no.5
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• pp.326-335
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• 2009

Fe based (Fe$_{68.2}$C$_{5.9}$Si$_{3.5}$B$_{6.7}$P$_{9.6}$Cr$_{2.1}$Mo$_{2.0}$Al$_{2.0}$) amorphous powder, which is a composition of iron blast cast slag, were produced by a gas atomization process, and sequently mixed with ductile Cu powder by a mechanical ball milling process. The Fe-based amorphous powders and the Fe-Cu composite powders were compacted by a spark plasma sintering (SPS) process. Densification of the Fe amorphous-Cu composited powders by spark plasma sintering of was occurred through a plastic deformation of the each amorphous powder and Cu phase. The SPS samples milled by AGO-2 under 500 rpm had the best homogeneity of Cu phase and showed the smallest Cu pool size. Micro-Vickers hardness of the as-SPSed specimens was changed with the milling processes.

• Journal of Powder Materials
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• v.15 no.4
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• pp.285-291
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• 2008

Fe based ($Fe_{68.2}C_{5.9}Si_{3.5}B_{6.7}P_{9.6}Cr_{2.1}Mo_{2.0}Al_{2.0}$) amorphous powder were produced by a gas atomization process, and then ductile Cu powder fabricated by the electric explosion of wire(EEW) were mixed in the liquid (methanol) consecutively. The Fe-based amorphous - nanometallic Cu composite powders were compacted by a spark plasma sintering (SPS) processes. The nano-sized Cu powders of ${\sim}\;nm$200 produced by EEW in the methanol were mixed and well coated with the atomized Fe amorphous powders through the simple drying process on the hot plate. The relative density of the compacts obtained by the SPS showed over 98% and its hardness was also found to reach over 1100 Hv.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.273-276
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• 2005

Packing characteristics of amorphous alloy particles were investigated by scanning electron microscopy, compositional analysis, micro-hardness test and finite element method (FEM). Electroless Ni-plating was made on the surface of the Cu-based amorphous particles before consolidation in ambient atmosphere at an intermediate region of glass transition and crystallization temperatures $(T_g\;and\;T_x)$. Some parts of the Ni-layer in the interfaces of the consolidated particles disappeared, while some of them still remained without appreciable change in compositions. No cracks or fractures were found in the particles, which may occur at low temperatures below or near $T_g$ as anticipated by the FEM analysis. Crystallization and change in hardness were not observed after consolidation.