Abstract
Molten aluminum in which excess hydrogen I.3 to I.5 cc/Ioo g had dissolved was solidified unidirectionally and water quenched in the course of solidification. A (liquid + hydrogen pore) region is formed in the liquid ahead of the solid-liquid interface. Pores are formed before end of solidification. Pores in the region are coarse near the interface and become finer with distance from the interface. A coarse and elongated pore near the interface is that incorporated with two or three pores. Pores are formed on oxides or inclusions in the melt and trapped by the advancing interface before floating away. The trapped pores incorporate with pores in the region ahead of the interface and grow into elongated cylindrical ones. Molecular hydrogen is condensed at the interface, while atomic hydrogen in solution shows a contrary tendency.
