• Journal of Powder Materials
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• v.1 no.2
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• pp.145-152
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• 1994

Atomizing mode and powder characteristics of CuA1Ni base shape memory alloy in rotating disk atomization were investigated in accordance with disk materials and additional elements. Produced powders were classified into two types of spherical and flake shape. In the case of CuAlNiBTi and CuAlNiZr alloy, high yield rate and fine powder were obtained. This tendency was same when we used oxide coated disks. We concluded that this results were steno from the wetting characteristics change between molten metal and disk surface. Especially, due to the reactive properties of Ti and Zr with ceramic disk, the change of atomizing appearance and powder characteristics were noticeable.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.381-387
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• 2000

Si3N4/stainless steel 316 joints with Ni buffer layer were fabricated by direct active brazing method (DIB) using Ag-Cu-Ti brazing alloy only and double brazing method (DOB) using Ag-Cu brazing alloy with Si3N4 pretreated with Ag-Cu-Ti brazing alloy. For the joint brazed by DIB method, Ti was segregated at the Si3N4/brazing alloy interface, but was not enough to form a stable joint interface. In addition, large amounts of Ni-Ti inter-metallic compounds were formed in tehbrazing alloy near the joint interface, which could deplete the contents of Ti involved in the interfacial reaction. However, for the joint brazed by DOB method, segregation of Ti at the joint interface were enough to enhance the formation of stable interfacial reaction products such as TiN and Ti-Si-Ni-N-(Cu) multicompounds, which restricted the formation of Ni-Tio inter-metallic compounds in the brazing alloy during brazing with Ni buffer layer. Fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was much improved by using DOB method rather than DIB method. It could be deduced that the differences of fracture strength of the joint with Ni buffer layer depending on brazing process adapted were directly affected by the formation of stable joint interface and the change in microstructure of the brazing alloy near the joint interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of interface. It was found that fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was gradually reduced as the thickness of Ni buffer layer in the joint was increased from 0.1 mm to 10 mm. It seems to due to the increased residual stress in the joint as the thickness of Ni buffer layer is increased. The maximum fracture strength of Si3N4/S.S 316 joints with Ni buffer layer was 386 MPa, and the fracture of joint was originated at Si3N4/brazing alloy joint interface and propagated into Si3N4 matrix.

• Journal of Powder Materials
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• v.6 no.4
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• pp.270-276
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• 1999

Ti-Ni-Cu alloy powders were fabricated by ball milling, and the properties of these powders were characterized. Mixed 50Ti-(50-x)Ni-xCu powders of 5 to 10at.%Cu composition were milled for 100 hours using SUS 1/4" balls in argon atmosphere. Ball to powder ratio was 20:1 and rotating speed was 100 rpm. Tensile strength, microstructure and phase transformation of ball milled Ti-(50-x)Ni-xCu powders were studied. After 100 hours milling, Ti, Ni and Cu elements were alloyed completely and an amorphous phase was formed. Amorphous phase was crystallized to martensite(B 19') and austenite(B2) after heat treatment for 1 hour at $850^{\circ}C$. As the Cu contents were increased, tensile strength of extruded 6061Al/TiNiCu was decreased, and B19'martensite phases In the TiNi particles were the causes of high tensile stress of extruded 6061Al/TiNiCu.NiCu.

• Korean Journal of Metals and Materials
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• v.49 no.4
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• pp.298-303
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• 2011

Mg-23.5 wt%Ni-xwt%Cu (x = 2.5, 5 and 7.5) samples for hydrogen storage were prepared by melt spinning and crystallization heat treatment from a Mg-23.5 wt%Ni-5 wt%Cu alloy synthesized by the gravity casting method. They were then ground under $H_2$ to obtain a fine powder. Among these samples the Mg-23.5Ni-2.5Cu sample had the highest hydriding and dehydriding rates after activation. The Mg-23.5Ni-2.5Cu sample absorbed 3.59 and 4.01 wt%H for 10 and 60 min, respectively, at 573K under 12 bar $H_{2}$. The activated 88(87.5Mg-10Ni-2.5Cu)-$5Nb_{2}O_{5}-7NbF_{5}$ sample absorbed 2.93 wt%H for 10 min, and 3.14 wt%H for 60 min at 573K under 12 bar $H_{2}$.

• Journal of the Korean institute of surface engineering
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• v.28 no.4
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• pp.243-254
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• 1995

The fabrication process of Cu-base anode for replacing Ni-base anode of molten carbonate fuel cell was investigated. Electrochemical performance and thermal stability of Cu-base anode were also investigated. Green sheet was prepared by mixing Cu and Ni powder with 1.5wt% methylcellulose and 100wt% water. The pore-size distribution of the Cu-base anode sintered at $800^{\circ}C$ for 30min showed almost uniform pore-size ranging from 4 to 20$\mu\textrm{m}$ and it was considered suitable for MCFC anode. Cu-Ni anode containing between 35 to 50wt% Ni exhibited current density of 111mA/$\textrm{cm}^2$ at 100mV overpotential and it was almost the some value for pure Ni anode. The sintering resistance of Cu-Ni increased with an increase of Ni addition. It was considered that the increase of sintering resistance was due to the decrease of diffusion rate of Cu and Ni with increasing the addition of Ni in Cu-Ni alloy.

• Journal of Korea Foundry Society
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• v.44 no.4
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• pp.97-102
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• 2024

In this study, the properties of Zr-14Cu-7.5Ni-2.6Al wide ribbon with amorphous structure and properties were analyzed using Hall effect, SEM-EDX, and XRD. Made by melt spinning method, this Zr-14Cu-7.5Ni-2.6Al based alloy ribbon is not more than 96 ㎛ thick and 100 mm wide. This amorphous alloy exhibited tensile strength of 1,641 MPa, yield strength of 1,541 MPa, elongation of 1% and elastic modulus of 98GPa. The bulk concentration, resistivity, and mobility values are midway between general heavy doping ceramics and metals, and they are about 100 times weaker than ordinary metals, so they are close to Si and have good electrical conductivity. In addition, folding tests were conducted at extreme temperatures, withstanding 150,000 times at -20℃, 300,000 times at 24℃, and 150,000 times at 60℃, with no folding defects observed. These results demonstrate the excellent durability and reliability of the Zr-14Cu-7.5Ni-2.6Al wide ribbon alloy and suggest the possibility of developing electronic products using this alloy.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.91-92
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• 2004

• Journal of the Korean Society for Heat Treatment
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• v.37 no.2
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• pp.79-85
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• 2024

The effects of annealing heat treatment and the addition of Cu element on the shape memory effect of the NiTi-based alloy were investigated by analyzing differential scanning calorimeter results and characterizing recovery rate through 3D scanning after Vickers hardness test. Through 3D scanning of impressions after Vickers hardness test, the strain recovery rates for specimens without annealing treatment and annealed specimens at 400, 450, and 500℃ were measured as 45.96%, 46.76%, 52.37%, and 43.57%, respectively. This is because as the annealing temperature increases, both B19' and NiTi₂ phases, which can impede martensitic transformation, are incorporated within the NiTi matrix. Particularly, additional phase transformation from R-phase to B19' observed in specimens annealed at 400 and 450℃ significantly contributes to the improvement in strain recovery rates. Additionally, the results regarding the Cu element content indicate that when the total content of Ni and Cu is below 49.6 at.%, the precipitation of fine B19' and NiTi₂ phases within the matrix can greatly influence the transformation enthalpy and temperature range, resulting in relatively lower strain recovery rates in NiTi alloys with a small amount of Cu element produced in this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.64-66
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• 1988

The present investigation has been performed on the manufacturing process of Ni-P doped W-Cu electric contacts by infiltration techniques. The addition of small amount of Ni-P alloy aimed at forming a rigid and homogeneous skeleton structure of W-powders which favours subsequent infiltration process of Cu-melts. The experimental results revealed that the small addition of Ni-P alloy appreciably enhances the sintering process of W at low temperatures (even at 1000$^{\circ}C$), simultaneously causing a considerable change of skeleton Morphology and its related best infiltration behaviour of Cu-melts.

• Journal of Korea Foundry Society
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• v.31 no.1
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• pp.26-30
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• 2011

For the fabrication of bulk near-net-shape Ti-Ni-Cu shape memory alloys, consolidation of Ti-Ni-Cu alloy powders are useful because of their brittle property. In the present study, $Ti_{50}Ni_{30}Cu_{20}$ shape memory alloy powders were prepared by gas atomization and martensitic transformation temperatures and microstructures of those powders were investigated as a function of powder size. The size distribution of the powders was measured by conventional sieving, and sieved powders with the specific size range of 25 to $150\;{\mu}m$ were chosen for this examination. XRD analysis showed that the B2-B19 martensitic transformation occurred in the powders. In DSC curves of the as-atomized $Ti_{50}Ni_{30}Cu_{20}$ powders as a function of powder size, only one clear peak was found on each cooling and heating curve. The martensitic transformation start temperature($M_s$) of the $25-50\;{\mu}m$ powders was $31.5^{\circ}C$. The $M_s$ increased with increasing powder size and the difference of $M_s$ between $25-50\;{\mu}m$ powders and $100-150\;{\mu}m$ powders is only $1^{\circ}C$. The typical microstructure of the rapidly solidified powders showed cellular morphology and very small pores were observed in intercellular regions.