Fabrication of Lotus-type Porous Ni-(15, 28 and 31) at.% Al Alloys by Unidirectional Solidification in Hydrogen Atmosphere

摘要

Lotus-type porous Ni- (15, 28 and 31) at.% Al alloys whose long cylindrical pores are aligned in one direction were fabricated by continuous zone melting technique under high-pressure gas of hydrogen of 2.5 MPa. A part of 5-10 mm in length of the rod in the vicinity of the coil was melted by high frequency induction heating, and was moved downwards by electric motors at a constant velocity of 330 μms~(-1) to 500 μms~(-1) for unidirectional solidification. The pores are formed as a result of precipitation from the supersaturated hydrogen gas when the liquid metals dissolved with gas atoms is solidified. The porosity and the pore size decrease with increasing aluminum content. An increase of solidification velocity from 330 μms~(-1) to 500 μms~(-1) leads to a decrease of pore diameter and an increase of pore number in the porous Ni-28at%Al.