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金敎漢 영남이공대학 1983 論文集 Vol.12 No.-
The effects of annealing and subzero treatment on thermal dilation of the Al-Al_3Ni eutectic composite were studied in relation to the residual stress and matrix yielding. For the composite annealed at 500℃ for 1hr, the heating curve forms a hysteresis loop with cooling curve on the test up to 300℃, and a small region of inflection is observed on each curve. By the subzero treatment at-196℃ for 10min, the inflection temperature on heating is lowered, but on cooling, it remains unchanged and no hysteresis loop is formed. In the temperature range which reaches the inflection region on heating and cooling tests, the fiber and the matrix undergo elastic deformation. The matrix begins to yield at the inflection on the heating curve of the subzeroed composite, the inflection region is observed near room temperature corresponds to the matrix yielding. The Al_3Ni fibers in the cycled material developed surface serrations which increased with maximum cycling temperature and number of cycles. The formation of these serrations is attributed to the increasing solubility of the Al_3Ni fibers in the matrix with temperature.
김교한,권오원,김형일 대한치과기재학회 1997 대한치과재료학회지 Vol.24 No.1
To define the optimum heat treatment temperature and time of the developed three types of low karat gold alloys, hardness test, DTA and x-ray diffraction methods were used. The results were as follows. *The optimum temperature of heat treatment was at 400℃ in K-Ⅰ, K-Ⅱ and K-Ⅲ alloys. *The proper time of age-hardening was 10 minute in K-Ⅰ alloy, and 10-30-minutes in K-Ⅱ alloys. *The stable phases of three types of low karat gold alloys were Ag-rich α₁ phase, Cu-rich α₂ phase and AuCuⅠ phase in case of K-Ⅰ alloy, and α1 phase and AuCuⅠ phase were coexisted in K-Ⅱ and K-Ⅲ alloy. *The cause of the decrease of hardness by overageing was the α₁ phase and AuCu Ⅰ phase, which were precipitated in the grain boundary.
김교한,김형일 대한치과기재학회 1996 대한치과재료학회지 Vol.23 No.2
The purpose of this study was to develop the dental casting low carat gold alloys based upon Au-Ag-Cu ternary alloy. Three types of low carat gold alloy containing 46, 55 and 66wt. % of gold, content respectively, which were balanced with total amount of Au plus Ag of 74wt. %, were melted and casted to evaluate the mechanical properties, corrosion resistance, melting range and cytotoxicity. The obtained results were summarized follows : ·In mechanical properties, the type K-Ⅱalloys, which was increased in the amount of Pt component, showed 115MPa of yield strength, 400MPa of ultimate tensile strength and 150 of vicker's hardness value and these values are higher than those of K-Ⅰ, K-Ⅲ alloy of 30% in yield strength, 50% in ultimate tensile strength and 10% in hardness value. ·Age hardening effect was confirmed in all three alloys. ·Melting ranges of these alloys were in the range of 910-1050℃ ·Higher corrosion resistance was confirmed in the potential range of oral cavith. ·The cytotoxicity of alloys was evaluated by the cell growth and morphologic changes, Each alloy showed normal growth rate and cellular morphology.