Electric current direct heating technique is applied for advanced austempering treatment which offers benefits such as savings of processing time and energy used. In order to apply this technique to the practical use, effect of start microstructure in spheroidal graphite ductile cast iron on both achieved temperature and created structure is examined in this study. In the same heating time, cast iron with ferrite matrix achieves at higher temperature during electric current direct heating compared with those of pearlite matrix cast iron. Pearlite structure, however, promotes carbon to permeate into austenite, so that carbon is easily concentrated in austenite in a few second. Excellent ADI is obtained in a short austenitizing less than two seconds by using electric current direct heating technique when pearlite base cast iron is employed for quick austempering treatment.

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  The bending fracture behavior and deformation structures of an as casted Ti-Al intermetallic compound were examined at room temperature and 973K. The bending fracture strength and the amount of deflection at 973K were superior to those at room temperature. On the specimen surface near the fracture obtained at 973K, many micro-cracks were observed and they showed a tendency to concentrate on lamellar colony boundaries and at their triple points. When internal microstructures near the fracture obtained at 973K were observed by using a transmission electron microscope. Many dislocations parallel to the interfaces between γ and α₂ plates and deformation twins formed at an angle to the interfaces were also observed. On the basis of the above results, the bending fracture mechanism of an as casted Ti-Al intermetallic compound at 973K was discussed.

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  Bending properties were investigated for ferrite-rimmed (F-rimmed) spheroidal graphite cast iron, which composesd of a fcrrite-rich structure at the surface layer and a pearlite-rich structure in the inner part of the cast iron, and compared with those of homogeneous ferrite-pearlite (F⋅P) cast iron with the same average ferrite fraction as the F-rimmed cast iron. The deflection at fracture of the F-rimmed specimen is considerably larger than that of the F⋅P specimen with the same bending strength. The F⋅P specimen fractures at a maximum bending load, while the F-rimmed specimen deflects more at the maximum load, giving higher ductility in bending than the F⋅P specimen. The bending deflection of the F-rimmed specimen with a defect such as a small hole or a V notch on the surface is also larger than that of the F⋅P specimen with the same defect. Charpy impact value of F-rimmed specimen is higher than that of the F⋅P specimen and the transition temperature of F-rimmed specimen is lower by about 60K compared with that of the F⋅Pspecimen. It has been found that the ductility and toughness of the F-rimmed specimen in bending is much higher than that of the F⋅Pspecimen with the same strength.

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  The continuous cooling transformation (CCT) behavior of multi-component white cast irons varying cobalt content from 0 to 10 mass % with 2.1 mass % C and 5 mass % of each alloying element Cr, Mo, W, V was investigated at two different austenitizing temperatures, 1273 and 1373K respectively. The noses of pearlite and bainite transformations shift to the shorter time side with an addition of cobalt, but the pearlite transformation retards once at 3 % Co, and then shifts again when added with more than 3 mass % addition. Regardless of cobalt content, the influence of austenitizing temperature on the pearlite transformation is small while the bainite transformation is retarded significantly at the higher austenitizing temperatures. The Ms temperature is decreased with the addition of cobalt up to 2 mass %, and then increased again. The Ms temperatures of the specimens austenitized at 1373K are lower than that austenitized at 1273K by 40 to 100K.

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  In squeeze castings, molten metal is compulsorily fed for shrinkage. The occurrence of the casting defects is therefore influenced by degree of the transferred pressure. In this study, the transfer ability of molten metal pressure in the squeeze castings of Al-Si alloys was investigated. The occurrence of shrinkage cavity was found to depend on the duration of the transferred pressure, not so much as the value of the transferred pressure. And the duration varied according to the Si contents of Al-Si alloys. For example, the duration on the castings of the eutectic Al-12Si alloy was longer than that of the hypoeutectic Al-6 % Si alloy. Because this duration was influenced by the solidification manner of Al-Si alloys, and the transfer ability of alloy solidified with the skin-formation type casting is higher than that of alloys solidified with mushy-formation type.

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  Using pure Fe-C-Si melt (3.4 mass % C and 1.9 mass % Si), we evaluated the influence of manganese and titanium on the microstructure and the tensile properties of cast iron. The pure Fe-C-Si melt was prepared from pure iron, electrode graphite (99.9 mass % C) and semiconductor grade Si (99.999 mass % Si) using a basic lined high frequency induction furnace. In this experiment the chemical composition of manganese and titanium has been fixed within the range of commercial grade cast iron. As the result, the addition of manganese or titanium does not affect the graphite morphology but the matrix of cast iron. Both manganese and titanium in cast iron promote ferritization according to the balance of the nitrogen content.

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