• Transactions of Materials Processing
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• v.13 no.8
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• pp.696-703
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• 2004

The purpose of this study is to examine the bulk/sheet forming characteristics of bulk amorphous alloys in the super cooled liquid state. Recently it is reported that amorphous alloys exhibit stress overshoot/undershoot and non-Newtonian behaviors even in the super cooled liquid state. The stress-strain curves with the temperature-dependences as well as strain-rate dependence of Newtonian/non-Newtonian viscosities of amorphous alloys are obtained based on the previous experimental works. Then, those curves are directly used in the thermo-mechanical finite element analyses. Upsetting and deep drawing of amorphous alloys are simulated to examine the effects of process parameters such as friction coefficient, forming speed and temperature. It could be concluded that the superior formability of an amorphous alloy can be obtained by taking the proper forming conditions.

• Journal of Korea Foundry Society
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• v.30 no.5
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• pp.187-195
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• 2010

In this study, in order to obtain a useful guide line for design and production of automotive heat exchanger components made of 4343/3003/4343 aluminum clad sheets, it was aimed to improve the understanding about the grain refinement effect on brazing characteristic of the clad sheets. Al-10Ti master alloy was used for grain refinement of 3003 core alloy, and the Ti inoculation level was systematically changed up to 0.1 wt%. The three-layer aluminum clad sheets were fabricated by hot roll bonding process. The effect of grain refinement on brazing characteristic of the clad sheets was investigated by evaluating wettability, bonding strength and sagging resistance.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.12
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• pp.1995-2000
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• 1989

The ion beam system of 20keV C-W (Cockroft Walton) type composed of the AuGe alloy LMIS(Liquid Metal Ion Source) has been designed and constructed. For the fabrication of the ohmic contact to the n-GaAs, the ion beam extracted from the AuGe alloy source was implanted into the n-GaAs, and it was measured by contact resistivity. The stable AuGe ion beam(2.5\ulcorner/cm\ulcorner was obtained at the extraction voltage of 14.5kV. The measurements of the contact resistivity were done by the TLM (Transmission Line Model) method and the specific contact resistivity was found to be 2.4x10**-5 \ulcornercm\ulcornerfor the implanted sample by the 1.9x10**20/cm**3 and the annealed sample at 30\ulcorner for 2 min.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.1-5
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• 2008

Silicide formation process and the formation sequence were investigated in this study. It was postulated that the formation of the second silicide phase involves glass formation between the first silicide phase and Si given that a thin metal film is deposited on a Si substrate. The concentration of glass was assumed to be located where the free energy of the liquid alloy with respect to the first nucleated compound and solid Si (${\Delta}$G') is most negative. It was also mentioned that the glass concentration is close to the composition of the second phase in order to achieve the maximum energy degradation. It was shown that the minimum ${\Delta}$G' concentration can be estimated by interpolating the portion of the liquidus where the liquid alloy is in equilibrium with the two solid constituents, namely the first compound phase and Si, thereby forming a hypothetical eutectic.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.299-302
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• 2005

Semisolid A356 slurries were prepared by electromagnetic stirring casting and by inoculation of Al-5Ti-B master alloy. As stirring time and addition of Al-5Ti-B are different, the grain size of the primary phase is different. Through the experiment of rheocast in a Buhler horizontal die casting machine, it was found that the finer the equiaxed primary dendrites, the smoother the die filling and better cast quality. Small equiaxed primary dendrite also results in less liquid segregation on the surface.

• Journal of Surface Science and Engineering
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• v.29 no.4
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• pp.278-285
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• 1996

The structure of coating layer formed by hot dip Al-Cu alloy coating on Monel 1400 metal was studied. The coating layer consists of alloyed layer adjacent to the Monel 400 substrate and Al-Cu alloy. It was found that the hardness of coating increased with dipping time and heat treatment associated with the diffusion and the formation of intermetallic compound at the interface. However the thickness of coating layer was decreased at high dipping temperature due to tile higher viscosity of liquid coating alloy. Diffusion heat treatment at $600^{\circ}C$ after coating resulted in the disappearence of adhered Al(Cu) and $CuAl_2$ phases, and then they transformed into the new phases of CuAl and Al7Cu4Ni at coating layer.

• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.79-84
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• 2004

In this study, the electromagnetic vibration is adopted for modifying eutectic Si phase and reducing its size. The higher the current density and frequency of electromagnetic vibration(EMV), the finer the size of eutectic Si phase. The tensile strength and elongation of EMVed alloy were highly improved. Measured twin probability of EMVed alloy at a frequency of 1000 Hz was approximately six times as high as that of the normal alloy. The mechanism for the increase in twin density due to EMV during solidification could be supposed from the fact that the preferential growth along <112> in silicon was suppressed by preventing Si atom from attaching to the growing interface of Si phase and by changing the solid/liquid interfacial energy of silicon. According to the result of UTS test, because of modification of eutectic Si, UTS and elongation are highly increased.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1078-1079
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• 2006

The paper presents the possibilities of obtaining new composite materials based on sintered porous ceramics with particles and fibre of $Al_2O_3$ infiltrated by aluminum alloy. The EN AC - AlSi12 alloy features the matrix material, whereas the RF50AX-301 preform, of Saffil Automotive, was used as the reinforcement. Examinations of ceramics preforms permeability were made. Metallographic examination of composite materials made on light microscope and in scanning electron microscope show that aluminum alloys fill micropores in the matrix. New composite materials show twice higher value of hardness in comparison with matrix. Results indicate that it is possible to infiltrate porous ceramic with liquid aluminum alloy to obtain new composite materials were advantageous properties of each component are connected.

• Journal of Powder Materials
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• v.17 no.6
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• pp.489-493
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• 2010

Nickel-based and iron-based alloys have been developed and commercialized for a wide range of high performance applications at severely corrosive and high temperature environment. This alloy foam has an outstanding performance which is predestinated for diesel particulate filters, heat exchangers, and catalyst support, noise absorbers, battery, fuel cell, and flame distributers in burners in chemical and automotive industry. Production of alloy foam starts from high-tech coating technology and heat treatment of transient liquid-phase sintering in the high temperature. These technology allow for preparation of a wide variety of foam compositions such as Ni, Cr, Al, Fe on various pore size of pure nickel foam or iron foam in order for tailoring material properties to a specific application.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.379-384
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• 1997

Al-15Cu-lMg alloys have been directionally solidified in 3mm diameter alumina tubes under the conditions of $760^{\circ}C$ of furnace temperature and 12 cm/hr of furnace moving velocity(V). By analyzing the evolution of the temperature profiles along the alloy length, the position of the solid/liquid interface, temperature gradient(G) and local growth velocity (R) were determined. These growth characteristics were compared for 6, 10, 14 cm length alloys. Steady state growth region was obtained in 15 cm length alloy, not in 6, 10 cm.