Fabrication of lotus-type porous magnesium by continuous casting process

Lotus-type porous magnesium with long cylindrical pores aligned in the direction parallel to the transference direction was fabricated by the continuous casting technique at various transference velocities. The molten magnesium dissolving gas in a crucible was solidified continuously through cooled mold as being pulled down at a given velocity. The pore diameter and the pore number density were significantly affected by the transference velocity, although the porosity was not varied much. The increase in the transference velocity leads to a decrease in the pore diameter and an increase of pore number density. The porosity did not significantly vary with the transference velocity. The nonporous skin layer was observed near surface of solidified magnesium slab. The angle between the pore growth direction and the transference direction increased with an increase of transference velocity. This is attributed to the increase of cooling effect from the mold when the transference velocity increases. The thickness of skin layer perpendicular to the surface is affected by a change in not only the pore growth angle but also the distance between the surface and the pore in the axial direction of the pores.