Deoxidation behavior of molten copper was examined using carbonaceous deoxidizer (charcoal) sprinkled on the surface of molten copper containing high level oxygen. As a result, this process proved to be very unsatisfactory for practical use in terms of both the molten copper deoxidation yield and the deoxidation rate. It was found that the reason for this is that the Boudouard reaction CO₂+C → 2CO is slow and thus exhibits a rate-determining step. To solve this problem, Ar gas bubbling technique was employed to promote the Boudouard reaction, CO₂+C → 2CO, in the charcoal layer on the molten copper. This technique remarkably improved both the molten copper deoxidation yield and the deoxidation rate.

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  Fluid flow analysis was carried out to estimate the fluid velocity in the vacuum suction casting process or vacuum fluidity test. A pressure equation was derived by assuming piston flow in a vertical cylindrical tube for simplicity and was numerically solved. The fluid velocity was considerably affected by some factors such as the pressure difference between the tube and reservoir, flow resistance of air path, and tube diameter. An oscillation of the fluid occurred at a higher velocity because of its high inertia. The calculated results showed good agreement with the experimental results by water or mercury. In the case of fluid without solidification, this model can be applied to estimate the effects of the above factors on the fluid velocity.

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  Both experimental and theoretical works were performed to study the effects and the control of unidirectional solidification process on the pore size of the foamed aluminum. Analytical prediction showed that the growth and shape of pores formed during unidirectional solidification are affected by compromise between the solidification rate and the growing speed of pores in the region of molten aluminum. The slower the solidiflcation rate, the larger the cylindrical pores formed at the solid-liquid interface. This may be attributed to the pore incorporation with other pores in the liguid region to form larger pores in cylindrical shape.

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  The effects of silicon content on abnormal microstructures such as coarse α phase, massive structure and scattered structure, and the tensile strength of die castings, were investigated with Al-XSi binary alloys (X=5, 8, 11 mass %) and commercial alloys such as AC2A, ADC 10 and ADC 12 die castings fabricated by a 90 metric ton locking force cold chamber type die casting machine. In the microstructures of both Al-XSi binary alloys and commercial alloys, coarse α phase decreases and scattered structure increases with increasing silicon contents and shot-time-lag. In the case of wide temperature range between Al-Si eutectic and liquidus line such as Al-5 mass % Si and AC2A alloy, the abnormal microstructures mainly consist of coarse α phases and massive structures. On the other hand, in the case of narrow temperature range such as Al-11 mass % Si and ADC 12 alloy, the abnormal structure mainly consists of scattered structures. The tensile strength of both AC2A and ADC 10 alloys decreases with increasing shot-time-lag because of increasing coarse α phase. In the case of ADC 12 alloy die castings, the amount of dispersion for values of tensile strength is larger than that of the other two alloys because ADC 12 alloy die castings contain many scattered structures.

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  A modified coupled-diffusion method using iron interlayer was investigated for the surface modification of steels having a wear resistant vanadium carbide (VC) surface layer and a gradient distribution of the carbide volume fraction through the interlayer whose back surface was simultaneously bonded with the substrate material by diffusion treatment. Vanadium distribution profile showed a bending point at the vanadium concentration where σ phase appeared, indicating that the distribution of VC volume fraction depends on the distribution of vanadium concentration. The specimen subjected to the vanadium diffusion treatment at higher temperatures where σ phase disappeared and subsequent carbon diffusion at 1273 K, had a modified surface layer consisting of a VC layer with about 20 μm thickness on the top surface. The VC distribution gradually decreased toward the substrate. It is demonstrated that the specimens having such a microstrueture are expected to show a promising effect to diminish thermal stress concentration.

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  Surface composites of 7 mass % Mn steel with cast tungsten carbide particles were developed in this study. The wear-resistance was investigated by pin disk method. The results showed that the composites have excellent wear-resistance than white cast iron and high chromium cast iron. Wear-resistance increased with the decrease in the particle size of cast tungsten carbide, abrasive SiC and wear load. The wear mechnism of the surface composites was grinding and surface brittle falling of the carbide particles with repeated stress. Matrix is strengthened with the dissolution of the carbide and the addition of ferro-chrome particles to matrix. This was an important reason for the excellent wear resistance of the surface composites.

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