Energy absorbing materials with isotropic mechanical properties are necessary for landing gears of spacecrafts. Porous Al-10Si-0.3Mg alloys with an acorn shape are designed for JAXA small lander for investigating moon. The ordered cellular structure with the porosity of 94% is manufactured through a powder bed fusion process. Compression tests are carried out on the inclined plane. Acorn shaped porous aluminum alloys showed good energy absorption behavior on the inclined plane up to 20°. In addition, compression tests of the acorn shaped porous aluminum alloys are carried out on the plane with a hemispherical boulder. Experimental results can be explained using a theoretical calculation of the contact area between the acorn shaped specimen and the inclined plane or between the specimen and the boulder. Energy absorption diagram revealed that the absorbed energy became high at the compression on the small size of the boulder. It was found that the acorn shaped porous aluminum alloy had a potential as an energy absorbing material for the small lander on the moon.

Time-resolved X-ray tomography was performed to observe three-dimensional equiaxed-grain structure in Al-15mass%Cu alloy refined by inoculant TiB₂ particles. The time resolution of as short as 0.5 s was achieved by using a pink X-ray beam at a beamline BL28B2 of SPring-8. A filtering method using a phase field model was used for improving quality of reconstructed images, and consequently motion of equiaxed grains were observed in-situ. The time and spatial resolutions allowed to analyze the three-dimensional microstructural evolution. Nucleation events of α-Al preferably occurred in the melt of the bottom part, where the temperature was lower. The dendritic grains were formed during floating after the nucleation because of the buoyancy force. The floating equiaxed grains were stacked due to the floating, and the solid fraction of the stacked regions ranged from 0.11 to 0.19. The observations suggested that the coherency point of dendritic grains was less than 0.2. The observations also showed the grain motion influenced the formation of equiaxed grain structure.

The mold used in aluminum alloy casting has a high cost and a long production period. Therefore, as a new shaping method for casting, a pin screen mold was proposed in this study. The pin screen mold, which has a large number of pins with tips, can transfer arbitrary shapes by changing the distance between pins and height of pins. It was found that when the distance between the pins was small, the molten metal could be cast without leaking through the gaps between the pins. When the distance between the pins was large, the molten metal could be cast by lowering the temperature of the molten metal to form a semi-solid state. The pin screen mold could be used repeatedly, which is expected to reduce the cost of aluminum alloy casting.