• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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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.

• Journal of Welding and Joining
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• v.13 no.3
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• pp.134-146
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• 1995

Aluminium nitride(AlN) is currently under investigation as potential candidate for replacing alumium oxide(Al$_{2}$ $O_{3}$) as a substrate material for for electronic circuit packaging. Brazing of aluminium nitride(AlN) to Cu with Ag base active alloy containing Ti has been investigated in vacuum. Binary Ag$_{98}$ $Ti_{2}$(AT) and ternary At-1wt.%Al(ATA), AT-1wt.%Ni(ATN), AT-1wt.% Mn(ATM) alloys showed good wettability to AlN and led to the development of strong bond between brate alloy and AlN ceramic. The reaction between AlN and the melted brazing alloys resulted in the formation of continuous TiN layers at the AlN side iterface. This reaction layer was found to increase by increase by increasing brazing time and temperature for all filler metals. The bond strength, measured by 4-point bend test, was increased with bonding temperature and showed maximum value and then decreased with temperature. It might be concluded that optimum thickness of the reaction layer was existed for maximum bond strength. The joint brazed at 900.deg.C for 1800sec using binary AT alloy fractured at the maximum load of 35kgf which is the highest value measured in this work. The failure of this joint was initiated at the interface between AlN and TiN layer and then proceeded alternately through the interior of the reaction layer and AlN ceramic itself.

• Archives of Metallurgy and Materials
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• v.64 no.3
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• pp.949-952
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• 2019

The effects of different types of process control agents (PCA) on the microstructure evolution of Ni-based oxide dispersion-strengthened superalloy have been investigated. Alloy synthesis was performed on elemental powders having a nominal composition of Ni-15Cr-4.5Al-4W-2.5Ti-2Mo-2Ta-0.15Zr-1.1Y₂O₃ in wt % using high energy ball milling for 5 h. The prepared powders are consolidated by spark plasma sintering at 1000℃. Results indicated that the powder ball-milled with ethanol as PCA showed large particle size, low carbon content and homogeneous distribution of elemental powders compared with the powder by stearic acid. The sintered alloy prepared by ethanol as PCA exhibited a homogeneous microstructure with fine precipitates at the grain boundaries. The microstructural characteristics have been discussed on the basis of function of the PCA.

• Journal of Powder Materials
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• v.14 no.4
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• pp.230-237
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• 2007

The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, $TiH_{2}$ and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at $1200-1275^{\circ}C$ in vacuum atmosphere under $10^{-3}$ torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at $1275^{\circ}C$, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.78-89
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• 1997

This study has evaluated the weld metal solidification cracking behavior of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). Austenitic stainless steels(304, 310S) were also included for comparison. In addition, a possible mechanism of solidification cracking in the fusion zone was suggested based on the extensive microstructural examinations with SEM, EDAX, TEM, SADP and AEM. The solidification cracking resistance of Ni base superalloys was found to be far inferior to that of austenitic stainless steels. The solidification cracking of Incoloy 825 and Inconel 718 was believel to be closely related with the Laves-austenite (Ti rich in 825 and Nb rich in 718) and MC-austenite eutectic phases formed along the grain boundaries during solidification. Cracking in Inconel 600 was always found along the grain boundaries which were enriched with Ti and P. Further, solidifidcation cracking resistance was dependent not only upon the type of love melting phases but also on the amount of the phases along the solidification grain boundaries.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.

• Journal of Hydrogen and New Energy
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• v.8 no.1
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• pp.31-41
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• 1997

In order to investigate the mechanism of electrochemical hydrogenation reaction on Zr-based Laves phase hydrogen storage alloy electrodes, electrochemical charge/discharge characteristics, potentiostatic/dynamic polarizations and electrocehmical impedance spectroscopy(EIS) of Zr-Ti-Mn-Ni and Zr-Ti-Mn-Ni-M(M=Fe, Co, Al) alloys were examined. Electrochemical discharge capacities of the alloys were quite different with gas charge capacities. Therefore, it was considered that discharge capacities of the alloys depend on electrochemical kinetic factors rather then thermodynamic ones. Discharge efficiencies were increased linearly with exchange current densities. The results of potentiostatic/dynamic polarization measurements showed that electrochemical charge and discharge reaction of Zr-based Laves phase hydrogen storage alloys is controlled by charge transfer process at the electrode surface. The EIS measurements also confirmed this result.

• Smart Structures and Systems
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• v.6 no.1
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• pp.73-85
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• 2010

The potential offered by the thermo-mechanical properties of shape memory alloys (SMA) in structural engineering applications has been the topic of many research studies during the last two decades. The main issues concern the long-term predictability of the material behaviour and the fatigue lifetime of the macro structural elements (as different from the one of wire segments). The laboratory tests reported in this paper are carried out on bar specimens and they were planned in order to pursue two objectives. First, the creep phenomenon is investigated for two different alloys, a classical Ni-Ti alloy and a Cu-based alloy. The attention is then focused on the Cu-based alloy only and its fatigue characteristics at given temperatures are investigated. Stress and thermal cycles are alternated to detect any path dependency.

• Journal of Surface Science and Engineering
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• v.30 no.4
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• pp.262-271
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• 1997

Nickel-matal hydride(Ni-MH) batteries are receiving attention as non-pollunting. high performance rehargeable energy stoage system. The performance of Ni-Mh is significantly influenced by the hydrogen storage alloy materiels used as an anode material. Recently, having discharge capacities higher than the $AB_5$-type hydrogen storage alloys, the Zr-based $AB_2$-Type hydrogen storage alloys has remaining problems regarding cycle life and self-dischareg. These problems need to be solved by improvements in the alloy design and/or surface treatment. This work investiggates the effects the effects of surface property by fluorination on $Zr_{0.7}Ti_{0.3}V_{0.4}Mn_{0.4}Ni{1.2}$ composittion $AB_2$-Type hydrogen storage alloys. EPMA, SEM and AES techniques were used for surface analysis, and the crystal structure was characterized by constant current cycling test and potential sweep methods. Fluorination was found to be effective when La-was incorporated into the alloy, and has unique morphology, higher reactivity, and at the same time formed a protective film. Through, fluorination, the cycle life of an electrode was found to increase significantly, charge/discharge characteristics of the electrode the potential difference between the charge/discharge plateau, i.e polarization(overpotential)were improved.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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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.