In the present work, attempts were made to develop a new type of cast iron, stainless spheroidal carbide cast iron whose chemical composition is x%C-20%Cr-10%Ni-y%V-Fe. This cast iron exhibits excellent characteristics in corrosion and abrasive resistance. In this cast iron, the morphology of vanadium-carbide was observed to change from flower-like carbide to spheroidal carbide when a proper quantity of Ni-Mg alloy was added.
  After adding Ni-Mg alloy, when the melt is held at 1923K, spheroidal carbides are crystallized until 2700s When the melt is held 4200s or more, spheroidal carbides have a tendency to coagulate with each other and flower-like carbides are crystallized. We can conclude as follows.
1) In this cast iron, adding Ni-Mg alloy is effective for crystallizing spheroidal carbides.
2) When melt is held at 1923K after adding Ni-Mg alloy, fading of effect is slower than ductile cast iron.

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  In order to develop a new aluminum alloy composite which has a low thermal expansion rate and is machinable, the aluminum alloy composites reinforced with short potassium titanate fibers were fabricated. The fiber preform was fabricated and then infiltrated with the AC4A aluminum alloy melt by squeeze casting to fabricate the composite. The microstructure and thermal properties of the composites were investigated. Optical microscopy revealed that the fibers were homogeneously distributed in the alloy. However, the fibers were somewhat in a planar random arrangement parallel to the pressed plane when the fiber volume fraction was high. This is due to the forming of the preform by pressing the upper and bottom of it. The composites were easily machined by the commercial super alloy cutting tools: the composites have good machinability. The thermal conductivity of the composite decreased as the fiber volume fraction increased. At higher volume fraction, the thermal conductivity of the composite in the parallel direction to the pressed plane was higher than that in the transverse direction because of the planar random arrangement of the fibers. The thermal conductivity can be roughly estimated by Landauer‘s model. Average thermal expansion coefficient of the composite decreased as the fiber volume fraction increased. The difference of the thermal expansion coefficient between the parallel and transverse direction to the pressed plane is slight, and the experimental values are in good agreement with the theoretical values calculated by the rule of mixture. These results show that the reduction in the thermal expansion of the aluminum alloy can be accomplished by the reinforcement with the short potassium titanate fibers.

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  A new surface hardening technology for cast irons was developed by applying the friction stir process (FSP) in which the matrix can be controlled in the solid state using frictional heat. Flake graphite cast iron(FC300) and spheroidal graphite cast iron(FCD700) were used to investigate the validity of this new method.
  As a result, it has become clear that a Vickers hardness of about 700HV is obtained for both the flake graphite cast iron and spheroidal graphite cast iron, and that the hardness depends on the size and the density of the martensite phase. Moreover, the hardness can be controlled down to about 500HV by changing the stirring degree.
  For previous hardening methods, post surface-processing was required because a large distortion is generated. However, for this new method, a lot of advantages such as a higher surface hardness and no required post surface-processing are obtained.

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  The water heated and pressurized above the critical point (648K, 22.1MPa) is called supercritical water (SCW) and allows high solubility of organic substance in the water. As a result, the condition of SCW in this phase requires high corrosive-resistance for the reactor vessel materials, so that the practical application of this technology has been delayed. Fe based alloy is tried to applied for corrosion-resistance materials and the alloy indicates various corrosion-resistances due to a change of heat, pressure and chemical composition. In this study, the effects of Cr, Ni, and Mo addition on the corrosion-resistivity and corrosion-behavior of Fe based alloy was investigated.
  Cr addition of above 10.0 mass% on the alloy, Fe₂O₃ and FeCr₂O₄ produced a protective boundary. Moreover, Cr addition of above 15.0 mass% on the alloy produced a single Cr₂O₃ layer of the protective boundary and while remarkably decreasing the corrosion-rate under the condition of 10～ permittivity. Cr addition of above 25.0 mass% on the alloy produced a single Cr₂O₃ layer of the protective boundary over the condition of 10～ permittivity. The effect of Ni addition on the corrosion-rate of the alloy, which transformed the matrix from ferrite to austenite, was low value. By addition of Mo to the alloy, the production of pitting-corrosion was decreased. Moreover, Mo addition of 25.0 mass% or less on Fe-25%Cr alloy decreased the corrosion-rate.

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