발간논문

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Effects of addition of SiC to a WC-6%Co alloy on mechanical properties of the cemented alloy were investigated. The addition of SiC was made to the cemented alloy as a solid solution of WC-SiC. The cemented alloy containing less than 1% SiC showed good densification, and the transverse rupture strength of the alloy was increased considerably at the SiC content of 0.5% whereas the hardness of the alloy was decreased slightly. It is believed that the addition of SiC inhibited decarburization of WC which always occurs during the sintering process and contributed to the strengthening of the cemented alloy.

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Hyper-eutectic Al-Si alloys were irradiated with ultrasonic waves (24KHz) to investigate the refining effects of primary silicon crystals. The relationship between the refining rate and irradiation, and the unstability and fading have been studied at the several temperature ranges and the following results were obtained : 1) The grain sizes of primary silicon crystals have been refined about the half of the orginal size and stabilized more by ultrasonic wave irradiations. 2) The most efficient temperature of melts for the irradiation was 100℃ higher than the melting point of the sample.

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Flaws of a new shape in anodic Ta₂O_5 films on tantalum foils formed in aqueous solutions of phosphoric acid were observed by electron microscopy. A mechanism for the formation of the flaws is proposed by the present study. Modes of scintillation were dependent upon anodizing solutions used. Crystals formed during anodization of tantalum foils were identified as β-Ta₂O_5. Scintillation voltages at reanodization after MnO₂ application were closely related to flaws and stresses in the anodic oxide films. Namely, scintillation voltages decreased with increasing number of flaws and increasing stresses in the films.

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Lead fluoborate solution was mainly used as an electrolyte solution. Pb and Cu anodes connected separately as a complex anode. Then, by the control of its dissolution in the electrolyte the constant amounts of metallic ions in the electrolyte were maintained during Pb-Cu alloy deposition on the cathode, so that homogeneous layer of deposition and constant metallic contents of the deposition could be obtained. In this study, the metallic contents in the deposition layer was compared to the metallic ion contents in the electrolyte. The dissolution amounts of anodes could be controlled by the adjusting the electric resistance of anodes, then, the amounts of dissolution and deposition were compared. Finally, the structure of deposition layer was studied by metallographic and X-ray techniques. The dissolution amounts of anodes should be easily controlled by the controlling of electric resistance of anodes which are connected each other. When the deposition amount of copper was not the same amount of dissolution from copper anode, the amount of copper ion in electrolyte can be changed until the amount of deposition and dissolution are both the same. Therefore, the desirable metallic contents of deposition could be obtained by the control of dissolution of anodes. Copper could be deposited in the lattice of lead while copper content in deposition layer is small enough, but an indefinite phase could be formed when copper content in the deposition layer is in excess.

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The present study attempted to achieve a deeper understanding of the effect of stress on graphitization as well as solidification in malleable cast iron. White cast iron was supercooled and its grain size was refined by applying stress by means of centrifugal force. Nucleation capacity of malleable cast iron increased with increasing stress and the activation energy of nucleation was ranged from 25,000 to 35,000 ㎈/㏖. Furthermore rate of graphite growth depend in turn upon nucleation. Graphite growth rate increase as nucleation capacity increase and its activation energy for graphite growth was ranged from 22,000 to 31,000 ㎈/㏖ in the heats examined.

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