The effects of pin-fins added to plate-shaped aluminum castings on their solidification characteristics were numerically examined by heat transfer and solidification simulation, and concepts for the casting designs of aluminum heat sink were also investigated. In the end effects E/T (E : end-effective range, T : baseplate thickness) of plate-castings with added pin-fins, there were differences depending on the casting and mold materials or pin-adding conditions. These findings suggested that the solidification characteristics of the castings are estimable and comparable using the end effects. Meanwhile there was a tendency for conditions with greater end effects to require longer solidification time. There were cases where liquid isolation occurred in pin-fins when solidification time was extremely long. It is considered that the conditions with these solidification processes may be unsuitable for manufacturing process using castings. In addition, it was suggested that the plot of heat-exchanging performance versus the end effects in aluminum heat sink may be useful for casting design, and many conditions have the potential to provide greater end effects by increasing the initial mold temperature.

  Hyper eutectic Al-Si alloys are used for making pistons and cylinder blocks due to their good wear resistance. However, the primary silicon free zone (PSFZ) is formed at rapidly cooled areas. Thus in this study, attempts were made to clarify the formation mechanism of PSFZ. Solidification was carried out using Al-17%Si alloy without phosphorus, and the following results were obtained.

  The primary silicon phase was nucleated on the chiller. All other areas were PSFZ. This finding suggested that coupled growth occurs in the PSFZ area because the primary silicon phase cannot grow. The reason for this could be explained by considering the relationship between the growth velocity of primary silicon and aluminum atom transfer rate.

  In this study, a three-layered functionally graded porous ADC12 aluminum alloy with different pore structures was fabricated by varying the amount of blowing agent added and amount of gases in ADC12 aluminum alloy die castings as starting materials. From X-ray computed tomography (X-ray CT) observations of the pore structures of the fabricated three-layered functionally graded porous ADC12 aluminum alloy, it was found that the fabricated porous aluminum alloy had three layers, namely layer A (high porosity and large pore diameter), layer B (middle porosity and small pore diameter), and layer C (low porosity and small pore diameter). The deformation of the fabricated three-layered functionally graded porous ADC12 aluminum alloy during compression tests started from the low strength layer A, and thereafter the middle strength layer B and high strength layer C sequentially deformed. The stress-strain curves during compression tests revealed that three plateau regions appeared independently in the three-layered functionally graded porous ADC12 aluminum alloy, and these correspond to the plateau regions appearing in uniform porous aluminum alloy with almost the same pore structure in each layer. The three plateau regions of the three-layered functionally graded porous ADC12 aluminum alloy had almost the same plateau stresses as the corresponding plateau regions of the uniform porous aluminum alloy.