• Journal of the Korean Vacuum Society
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• v.7 no.s1
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• pp.50-56
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• 1998

Ion beam assisted deposition (IBAD) was successfully used to produce a dense and ultra-adherent Hydroxyapatite (HA) film on titanium alloy and alumina. Recently it is also proved that the HA coatings on alumina substrate treated with 20 ppm $AgNO_3$ had the structure of $(Ag, Ca)_10(PO_4)6(OH)_2$, which exhibited excellent antimicrobial effects. The present paper aims to morphlogically characterize the adhesion of macrophages on newly developed Ag-HA coated alumina and Ti6A14V substrates and to evaluate the biocompatibility of the coatings in vitro. It can be found that the cell number on alumina of the concentration of $AgNO_3$ in the treatment, the cell number on Ag-HA coatings decreased. Up to 20 ppm $AgNO_3$ by Ag-treatment, the morphological development of the cells on Ag-HA coating was similar to that of the cells on HA coating, suggesting the biotolerance of the Ag-HA coatings.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.457-461
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• 2004

The thermomechanically treated $Ti-45.4\%Al-4.8\%Nb(at\%)$ alloy was oxidized between 800 and $1000^{\circ}C$ in air, and the oxidation characteristics were studied. The dissolution of Nb in the oxide scale was observed from the TEM study. The Pt marker test revealed that the oxidation process was controlled by the outward diffusion of Ti ions and the inward diffusion of oxygen ions. During oxidation, the evaporation of Nb-oxides was found to occur to a small amount. Niobium tended to pile-up at the lower part of the oxide scale, which consisted primarily of an outer $TiO_2$ layer, and an intermediate $Al_{2}O_{3}-rich$ layer, and an inner mixed layer of ($TiO_{2}+Al_{2}O_{3}$).

• Journal of the Korean Society for Nondestructive Testing
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• v.3 no.2
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• pp.5-12
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• 1984

The purpose of this paper is to decide volume of crack by AE source wave analysis. The material studied in this paper was Titanium Alloy. Transient wave memory has 50 nano sampling time. The response function of specimens and transducer was obtained experimentally by use of specimens and transducer was obtained experimentally by use of breaking pencil lead as a reference simulated AE source, and the source waves were dertermined in terms of energy release-time functions explicitly through a time domain deconvolution. From experimental results, we can determine size of cracked volume.

• Journal of Powder Materials
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• v.5 no.4
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• pp.340-344
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• 1998

Along with the growth of conventional ferrous powder metallurgy (PM), PM of aluminum alloys has been intensively investigated in Japan. Although rapidly solidified aluminum alloy powder was first used in the USA,/sup 1)/ commercialization for consumer market was first realized in Japan./sup 2)/ In order to achieve the viable cost-performance including Near Net Shape (NNS) formability, we developed three processes, powder extrusion, powder forging and sintering. The new powder extrusion process does not use either capsulation or vacuum degassing. The new powder forging does not need lateral flow. The new sintering process does not use liquid phase. The performance achieved by the processes is outstanding mechanical or physical properties that has potential to substitute cast iron, steel, titanium Metal Matrix Composite (MMC) or Ingot Metallurgy (IM) aluminum alloys. Cooperation with customers, powder suppliers and research associations contributed to the advancement of PM aluminum alloys in Japan.

• Journal of Hydrogen and New Energy
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• v.7 no.1
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• pp.39-44
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• 1996

The discharge capacity of V-Ti-Ni(V-rich) metal hydride electrode during the charge-discharge cycling was investigated in KOH electrolyte. All electrodes were degraded within 25 cycles. To investigate the cause of the degradation phenomena impedance measurements were performed by using E.I.S(electrochemical impedance spectroscopy). The surfaces of the degraded electrodes were examined by Auger electron spectroscopy (AES). It was observed that all electrodes were covered with oxygen from the surface to the bulk, titanium was enriched near surface, and vanadium was dissolved from the surface to the bulk.

• Journal of the Semiconductor & Display Technology
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• v.14 no.2
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• pp.47-52
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• 2015

In this paper, the performance of uncoated- and Titanium nitride aluminium TiAlN-PVD coated- carbide twist drills were investigated when drilling aluminium alloy, Al 6061. This research focuses on the optimization of drilling parameters using the Taguchi technique to obtain minimum surface roughness and thrust force. A number of drilling experiments were conducted using the L9 orthogonal array on a CNC vertical machining center. The experiments were performed on Al 6061 material l blocks using uncoated and coated HSS twist drills under dry cutting conditions. Analysis of variance(ANOVA) was employed to determine the most significant control factors. The main objective is to find the important factors and combination of factors influence the machining process to achieve low surface roughness and low cutting thrust force. From the analysis of the Taguchi method indicates that among the all-significant parameters, feed rate are more significant influence on surface roughness and cutting thrust than spindle speed.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.304-309
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• 2000

Strain gage method is used to evaluate the mode I dynamic stress intensity factor of marging steel(18Ni) and titanium alloy(Ti-6A1-4V). To decide the best strain gage position on specimen, static fracture toughness test was performed. Then instrumented charpy impact test and dynamic tensile test was performed by using strain gage method for evlauating dynamic stress intensity factor. Strain gage signals on the crack tip region are used to calculate the stress intensity factors. It is found that strain gage method is more useful than method by using load which is obtained from impact tup to assess dynamic characteristics such as dynamic stress intensity factor.

• Proceedings of the KOSOMBE Conference
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• v.1989 no.05
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• pp.9-12
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• 1989

A preliminary study has been conducted to demonstrate the effect of laser heat treatment on Ni Ti alloy dental arch wires ($0.016"\;{\times}\;0.022"$ and $0.018"\;{\times}\;0.026"$, rectangular shape). Changes in mechanical and thermal properties and surface morphologies are investigated by using optical and scanning electron microscope (SEM), energy dispersive x-ray microprobe analysis(EDX), differential scanning calorimeter (DSC), and micro hardness tester. The results indicate that the laser can affect the thermal equilibrium state of the localized surface. Titanium rich surface film is formed by the laser treatment. The surface film and rapidly resolidified underlying structures show better chemical resistance than the matrix material. Phase transition temperatures which are related to shape recovery temperatures are changed after laser treatment. Hardness of resolidified area and heat affected zone are lower than before treatment.

• Journal of Surface Science and Engineering
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• v.53 no.2
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• pp.53-58
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• 2020

In this study, we developed plasma electrolytic oxidation (PEO) process for aluminum 7075 alloy to improve the corrosion and mechanical properties. The electrolyte consists of potassium hydroxide and sodium silicate. Additionally, sodium stannate was added into the electrolyte to investigate its effect on PEO film formation. Titanium was used as the counter electrode. Plasma generation voltage reduced from 300V to 150 V by adding 4 g/L of sodium stannate. The thin oxide films were observed by SEM(Scanning Electron Microscopy)/EDS (Energy Dispersive Spectroscopy) for quantitative and qualitative analyses. XRD (X-ray diffraction) and XRF (X-ray Fluorescences) analyses were also carried out to identify oxide layer on aluminum 7075 surface. Vicker's hardness test was performed on the PEO-treated aluminum 7075 surface.

• Corrosion Science and Technology
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• v.15 no.4
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• pp.153-158
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• 2016

Light metal alloys of Mg, Ti, and Al undergo environmentally assisted cracking (EAC). Passive film breakdown and pitting are not only precursor events for stress corrosion, but can accelerate hydrogen evolution that is responsible for hydrogen embrittlement. This is clearly demonstrated in the case of Mg and Ti alloys. The so-called innocuous precipitates, which do not directly participate in either alloy strengthening or EAC can be effective precursors for initiating EAC. This aspect is highlighted using high strength aluminium alloys. Such behaviours lead to a paradigm shift in the design of alloys with resistance to EAC.