Local pressurization in die casting is a squeeze technique developed for minimizing the shrinkage porosity of Al alloy castings. However some defects, such as segregation stillremain in the castings pro-duced by this method. In this investigation, a study for local pressurization was carried out with a specially designed permanent mold to examine macrosegregation of copper for two kinds of Al-Si-Cu alloys with different solidification modes. The results analyzed by ICP illustrate that segregation under the pressurization pin tip is negative and easily occurs for AC4B rather than for ADC12 alloy. The degree of segregation differs with position from the pin tip in the casting and is affected by the solid fraction of the interdendritic Iiquid flowing zone for AC4B. Negative segregation in ADC12 only occurred at the annular position about 5mm below the pin tip and was not affected by pressurization timing. On the contrary, there appears positive segregation of copper in the upper zone around the pin. Both negative and positive segregation are caused by the flow of enriched liquid in the dendritic network or solid-liquid frontier during pressurization.

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  CO₂ laser beam was applied to the cladding of high chromium cast iron on carbon steel by a preplaced powder method. The hardness and microstructure of the clad layer were investigated by changing the power of laser, number of clad layers and overlapped width of the laser beam. The average hardness of the clad layer was 500∼600 HV0.1 under the following conditions : laser power of 2300 W to 2900 W, cladding speed of 400 mm/min, defocusing distance of 30 mm, oscillation width of 7 mm and argon gas shielding. The microstructure of the clad layer showed fine dendrites with secondary dendrite arm spacing of 2μm and fine eutectic carbides because of their rapid solidification. A heat affected zone was produced near the clad layer on the surface of the carbon steel and their martensitic structure was observed. The clad layer was then heat treated again with CO₂ laser beam, but the hardness of the clad layer did not change. EPMA line analysis indicated that an alloyed layer with 20μm in thickness exists between the clad layer and substrated base metal. These results suggest that the CO₂ laser beam cladding of high chromium cast iron is a useful surface treatment process.

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  To investigate whether it is possible to predict filling behavior by the observation of flow marks, intentionally generated flow marks and porosity in aluminum casting produced by high pressure die casting with a low temperature mold were investigated by the blistering test, gas analysis, mold filling analysis and solidification analysis. As a result, it was found that the final filling behavior near the gate can be predicted by the observation of flow marks. In addition, the flow marks were thought to be a high density and low gas content region with good feeding state of molten metal. Also, porosity distribution predicted by solidification analysis agreed comparatively well with real porosity distribution measured with a CT scanner.

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  The surface hardening technology based on electron beam welding has extended the possibilities for improving the wear and heat resistance of an aluminum alloy s. In this paper, aluminum copper silicon casting alloys containing 0 to 30 mass% copperand 0 to 16 mass% silicon and these alloys remelted using electron beam welding are made for studying the influence of copper and silicon components and processes, remelting and casting on wear properties.
  It is found that Al-4 mass% Si-Cu alloys has good wear resistant property, even in any mount of copper. And a wear resistant property of remelting alloys is superior to that of casting alloys.

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  To produce partially composed metal matrix composites, namely discontinuous MMCs, a spontaneous infiltration process was examined. The preforms of interpenetrated composites with SiC particles were infiltrated without pressure using Al-Si melts containing Ca or Mg. The preforms were fabricated using waterglass binder containing Fe₃O₄ powder. As the infiltration process is controlled by a wetting phenomenon, we studied this technique based on reactive wetting.
  The preforms were sintered in a Tamman tube at 1173K before infiltration and then infiltrated in air at 1173 to 1273K. In some experiments, pure aluminum powder was placed on the intered SiCp to increase the interfacial area and the interfacial reaction. The combined conditions resulted in complete infiltration without pressure in air at 1173 K. The infiltration rate was evaluated by measuring the weight changein the melt using a load sensor. It was confirmed that the infiltration was completed within 300 s while the preforms were held in the melt.

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  The applicability of the Cooper-Eaton equation for green sand molding was examined using various base sands under different bentonite additions. A quantitative analysis was carried out by evaluating the correlation between compaction behavior and morphological properties of sand to investigate the influence of grain morphology on sand compaction behavior. The rearrangement mechanism of compaction can be quantitatively related with four factors of the morphological properties of sand grain by using two linear equations. Among various parameters, shape factors, size and shape distribution of sand particles are shown to be significantly influential on the rearrangement mechanism.

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