• Journal of the Korean Society for Heat Treatment
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• v.11 no.3
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• pp.177-185
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• 1998

The purpose of this research is to investigate the effects of Co, Co-Ti addition on the sintering characteristic of $(Ti_{1-x}Alx)N$ material synthesized by the direct nitriding method for a application as a cermet material. The observed shrinkage rates of $(Ti_{1-x}Alx)N$ pellets increase with the additive (Co, Co-Ti) content, temperature and time, and also the pellets with the same additive content exhibit the shrinkage behavior that depends on the Ti/Al ratio. However, although the shrinkage rates in this study is the mast higher (36%), the density of the sintered $(Ti_{1-x}Alx)N$ pellet is below 80% density in theory because of the partial segregation and the dense band defect of AlCo compound. Consequentely, it is considered that Co was not effective as a binder material because the wettability of liquid Co metal on $(Ti_{1-x}Alx)N$ materials is poor, In $(Ti_{1-x}Alx)N$ with Ti-Co additive, the stoichiometric TiN is transformed by the under-stoichiometric TiNx(x<1.0) during sintering, leading to the good properties such as hardnees and hot oxidation.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.29-29
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• 1999

The synthesis of layered structures on the nanometer scale has become essential for continued improvements in the operation of various electronic and magnetic devices. Abrupt metal-metal interfaces are desired for applications ranging from metallization in semiconductor devices to fabrication of magnetoresistive tunnel junctions for read heads on magnetic disk drives. In particular, characterizing the interface structure between various transition metals (TM) and aluminum is desirable. We have used the techniques of MeV ion backscattering and channeling (HEIS), x-ray photoemission (ZPS), x-ray photoelectron diffraction(XPD), low-energy ion scattering (LEIS), and low-energy electron diffraction(LEED), together with computer simulations using embedded atom potentials, to study solid-solid interface structure for thin films of Ni, Fe, Co, Pd, Ti, and Ag on Al(001), Al(110) and Al(111) surfaces. Considerations of lattice matching, surface energies, or compound formation energies alone do not adequately predict our result, We find that those metals with metallic radii smaller than Al(e.g. Ni, Fe, Co, Pd) tend to form alloys at the TM-Al interface, while those atoms with larger atomic radii(e.g. Ti, Ag) form epitaxial overlayers. Thus we are led to consider models in which the strain energy associated with alloy formation becomes a kinetic barrier to alloying. Furthermore, we observe the formation of metastable fcc Ti up to a critical thickness of 5 monolayers on Al(001) and Al(110). For Ag films we observe arbitrarily thick epitaxial growth exceeding 30 monolayers with some Al alloying at the interface, possible driven by interface strain relief. Typical examples of these interface structures will be discussed.

• Korean Journal of Materials Research
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• v.4 no.4
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• pp.483-490
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• 1994

The effect of vanadium additions on the thermal stability of Al-TI alloy \vas investigated. Al- 8wt.%Ti and Al-8wt.%(Ti+V) alloys wirh different Ti to V atomic ratios of 3 : 1 and 1 : 1 were pre- pared by mechanical alloying. The steady states wwe obtalncd after mechanical alloy~ng for ltihours for all the alloy compositions. The mechanically alloyed powders were consolidaicd by vacuum hot pressing and thermal st.ability was investigated by hardness testing afrcr aging thc specimens at $400^{\circ}C$, $480^{\circ}C$, $550^{\circ}C$ for up to 1000hrs. It was confirmed that addit~on of V- increased the thermal stability of Al-Ti alloy by reducing coarsening rate of $Ai_{3}Ti$ intermetallic compound.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.374-379
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• 2011

Nano-powders of $Ti_3Al$ and $2Al_2O_3$ were synthesized from $3TiO_2$ and 5Al powders by high energy ball milling. A nanocrystalline $Al_2O_3$ reinforced composite was consolidated by pulsed current activated sintering within 2 minutes from mechanochemically synthesized powders of $Al_2O_3$ and $Ti_3Al$. Nanocrystalline materials, have received much attention as advanced engineering materials due to their improved physical and mechanical properties. The relative density of the composite was 99.5%. The average obtained hardness and fracture toughness values were 1510 kg/$mm^2$ and $9\;MPa{\cdot}m^{1/2}$, respectively.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.310-315
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• 2012

Nano-powders of 1.5TiAl and $Al_2O_3$ were synthesized from $1.5TiO_2$ and 3Al powders by high energy ball milling. Nanocrystalline $Al_2O_3$ reinforced composite was consolidated by pulsed current activated sintering within 2 minutes from mechanochemically synthesized powders of $Al_2O_3$ and 1.5TiAl. The relative density of the composite was 99.5%. The average hardness and fracture toughness values obtained were $1250kg/mm^2$ and $10MPa{\cdot}m^{1/2}$, respectively.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.99-102
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• 2003

Reactions between 48Sn-52In solder and under bump metallurgies(UBM) such as 100nm $Ti/8{\mu}m$ Cu and 300nm Al/400nm Ni(V)/400nm Cu have been investigated, and the shear strength of 48Sn-52In solder bumps on each UBM has been evaluated. While intermetallic compounds with two different morphologies were continuously thickened on Ti/Cu with repeating the reflow process, the intermetallics on Al/Ni(V)/Cu spalled into the solder with increasing the number of reflow times. The solder bumps on Ti/Cu exhibited higher shear strength than those on Al/Ni(V)/Cu.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.103-114
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• 1995

Plasma Transferred arc(PTA) hard facing process has been developed to obtain an overlay weld metal having excellent wear resistance. The effect of Ti, TiSi$_{2}$ and TiC powders addition on the surface of Aluminum alloy 5083 has been investigated with PTA process. This paper describes the result of test the performance of the overlay weld metal. The result can be summarized as follows 1. Intermetallic compound is formed on surface of base metal in Ti or TiSi$_{2}$ powder but the reaction with surface of base metal is little seen in TiC powder. 2. In formation of composite layer on aluminum alloy surface by plasma transferred arc welding process, high melting ceramics like TiC powder is excellent. 3. The multipass welding process is available for formation of high density of powder. But the more number of pass, the less effect of powder, it is considered, and limits of number of pass. 4. By increasing area fraction of TiC powder on Al alloy surface, in especially TiC powder the hardness increase more than 40% area fraction and 88% shows about Hv 700.

• Journal of the Korean Society for Heat Treatment
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• v.19 no.5
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• pp.249-256
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• 2006

Structural studies have been performed on precipitation hardening found in $L1_2$ ordered ${\gamma}^{\prime}-Ni_3(Al,Ti)$ alloys using transmission electron microscopy. A uniform solid solution of ${\gamma}^{\prime}-L1_2$ ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The ${\gamma}^{\prime}$ phase hardens appreciably by the fine precipitation of disordered ${\gamma}$. The shape of ${\gamma}$ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the ${\gamma}$ precipitates are perfectly coherent with the matrix ${\gamma}^{\prime}$ as long as the ${\gamma}$-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the ${\gamma}/{\gamma}^{\prime}$ interface followed by the step formation at the dislocations. The ${\gamma}$ precipitates become globular after the loss of coherency. The strength of ${\gamma}^{\prime}-Ni_3(Al,Ti)$ increases over the temperature range of experiment by the precipitation of fine ${\gamma}$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature.

• Korean Journal of Materials Research
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• v.30 no.2
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• pp.57-60
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• 2020

Titanium aluminides have attracted special interest as light-weight/high-temperature materials for structural applications. The major problem limiting practical use of these compounds is their poor ductility and formability. The powder metallurgy processing route has been an attractive alternative for such materials. A mixture of Ti and Al elemental powders was fabricated to a mechanical alloying process. The processed powder was hot pressed in a vacuum, and a fully densified compact with ultra-fine grain structure consisting of Ti₃Al intermetallic compound was obtained. During the compressive deformation of the compact at 1173 K, typical dynamic recrystallization (DR), which introduces a certain extent of grain refinement, was observed. The compact had high density and consisted of an ultra-fine equiaxial grain structure. Average grain diameter was 1.5 ㎛. Typical TEM micrographs depicting the internal structure of the specimen deformed to 0.09 true strain are provided, in which it can be seen that many small recrystallized grains having no apparent dislocation structure are generated at grain boundaries where well-developed dislocations with high density are observed in the neighboring grains. The compact showed a large m-value such as 0.44 at 1173 K. Moreover, the grain structure remained equiaxed during deformation at this temperature. Therefore, the compressive deformation of the compact was presumed to progress by superplastic flow, primarily controlled by DR.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.515-519
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• 2011

The purpose of this study was to determine the optimal firing condition and composition for $Al_2TiO_5$ crystal, which is suitable for stable coloration in glazes at high temperatures, using $Cr_2O_3$ as chromophore for the synthesis of $Al_2TiO_5$ system pigments. $Al_2TiO_5$ has a high refractive index and good solubility of chromophore in the $Al_2TiO_5$ lattice, making this structure a good candidate for the development of new ceramic pigments. Pigments were synthesized by using $Al_2O_3$ and $TiO_2$ mainly. Various amounts of $Cr_2O_3$ such as 0.01, 0.02, 0.03, 0.04 and 0.05 mole were also added. Each compound was synthesized at $1300^{\circ}C$, $1400^{\circ}C$, and $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigments were analyzed by XRD, SEM, Raman spectroscopy, UV and UV-vis. The changes in color as the result of applying 6 wt% of the synthesized pigments to lime barium glaze were expressed as CIE-L*a*b* values. A $Cr_2O_3$ 0.03 mole doped $Al_2TiO_5$ brown pigment was successfully synthesize at $1400^{\circ}C$, and the values of CIE-L*a*b* parameters were L* = 44.62, a* = 3.10, and b* = 17.25. In the case of the pigment synthesized at $1500^{\circ}C$, the brown color was obtained at 0.01 mole and 0.02 mole $Cr_2O_3$, and the CIE-L*a*b* values were 55.34, 1.73, 28.64, and 49.39, 0.51, 21.33, respectively. At $1500^{\circ}C$, the maximum limit of solid solution was 0.03 mole $Cr_2O_3$. The glazed sample showed green color, and the values of the CIEL* a*b* parameters were L* = 45.69, a* = -0.98, and b* = 20.38.