The significant features of closed cell aluminum foams are low density, high specific strength, high energy absorption, etc. These advantages are affected by the size, shape, and uniformity of cells in the foam. In order to improve the cellular structure of metal foams, foam stability of liquid metals to prevent rapture and drainage events has to be understood and controlled. A clear understanding of factors is therefore expected to improve quality and process control more easily.
  In this study, the influence of the temperature for adding foaming agent viscosity of the melt on foamability, and the growing mechanism of hydrogen bubbles in aluminum melt were investigated. Aluminum alloy foams were fabricated using the powder decomposition in the melt process and the unidirectional solidification method. As starting materials, Al-25mass%Cu-5mass%Si and Al-12.6mass%Si alloys were used. It was found that the temperature of foaming agent addition affected the number of cells and cell wall thickness. This effect was greater than those of viscosity and alloy components. Namely, the drainage of the liquid in foam film is the main factor for fabricating fine aluminum foam effectively.

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  Cast iron specimens containing different contents of component elements were prepared for bead-on-pleat test. The results show that the amount of pinholes increases with increasing C, Si, Mn, Ni and Cu contents, while the amount of pinholes decreases with increasing P, S, Cr, Mo and Mg contents. The following conclusions were obtained. (1) Graphitizing elements, such as C, Si, Ni, and Cu and oxide forming elements such as Mn, Si at the interface between graphite and matrix, tend to promote the generation of pinholes easily. (2) Elements with give oxidation resistance or graphite growth resistance to cast irons, elements which tend to form oxide film on the cast iron surface, elements which segregate near the eutectic cell boundary, and elements which form more stable oxides than carbon monoxide all tend to reduce pinholes.

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  Ti-Al based intermetallic compound materials have great potentials as a new functional material. Despite their great potentials, these materials are rarely applied in the industrial field. One of the main reasons may be because of the brittleness of the material. As an application of Ti-Al based intermetallic compounds, use as a surface reforming layer is feasible.
  Ti-Al based intermetallic compounds were coated on a spheroidal graphite cast iron (FCD) by self propagating high temperature synthesis (SHS) at several heating rates and compacting pressures of the powder compacts.
  As a result, it is found that increasing the heating rate promoted SHS. As far as compacting pressure was concerned, use of a compact press molded at 250MPa was found to produce reactiveness equivalent to or above 500MPa.
  The obtained coating layer showed hardness and wear resistance superior to FCD substrate.

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  Multi-component white cast irons are becoming increasingly popular as materials for rolling mill rolls due to its excellent wear resistance. In this research, influence of carbon (C) and chromium (Cr) contents on mechanical properties, hot wear properties and their correlation were investigated using Fe-5%Mo-5%W-5%V-5%Co-Cr-C alloy. Martensitic matrix was obtained in a wide area with Cr content more than 5% and carbon-balance (C_bal) of ±0.8%. Hardness was over 600HV. Ferrite or pearlite was formed in areas with low C_bal, and lamellar pearlite in areas with high C_bal and low Cr. Austenite was found to partially remain in 1%C-10%Cr iron. Macro-hardness and matrix hardness basically showed similar tendency and macro-hardness was higher than matrix hardness for pearlite matrix. The maximum tensile strength was 1006MPa in 1.5%C-2.5%Cr iron. Low matrix hardness and a large carbide content decreased tensile strength. Compressive 0.2% proof strength showed a maximum value of 2.14GPa in 1.5%C-7.5%Cr iron. Hardness of above 600HV and chemical composition of more than 5% and Cr content －1% to +1% C_bal content are desirable for achieving 0.2% proof strength necessary to withstand Hertzian contact stress in the finishing train of hot strip mill. Fracture toughness was high in high hardness areas and it decreases in cast irons with excess carbide and low matrix hardness. Wear resistance was basically better in cast irons with high hardness and high fracture toughness.

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