Fabrication of a lotus-type porous Al-Si alloy by continuous casting with a thermal decomposition method

Lotus-type porous A1-14 wt.%Si alloy was fabricated by continuous casting at a transference velocity of 10 mm|min-1 in vacuum and by adding Ca(OH)2 pellets to the crucible. The porosity and the pore diameter increased by varying the amount of Ca(OH)2 from 0.2 g to 0.6 g. In the case of 0.6 g Ca(OH)2, the average porosity was about 30 % and the average pore diameter was about 3.8 mm. XRD patterns of the pellets after continuous casting showed the Ca(OH)2 pellet did not decompose completely during continuous casting. The TG-DTA analysis showed that the Ca(OH)2 pellet decomposes more slowly than Ca(OH)2 powder. These results suggest that the Ca(OH)2 pellets gradually decomposed in the crucible during the continuous casting, which is suitable for the supply of hydrogen over extended periods.