Fabrication of porous Al-Cu alloys with aligned unidirectional pores by dipping pipes in melt and semi-solid slurry

Aligned seven pure aluminum pipes with internal diameter of 3 mm and wall thickness of 0.5 mm were dipped into Al-4 mass% Cu melt and semi-solid slurry. The specimen was cooled and solidified after holding times 0, 15 and 30 s. The pipes were bonded to the base metal with maintaining the shape of pipes by using the semi-solid base metal. An increase in solid fraction of the base metal is effective to avoid thermal damage of the pipes. Penetration of Cu into the pipe was found by EPMA analyses. Diffusion of Cu from the base metal to grain boundary of pipes decreases the liquidus temperature of a phase in the vicinity of the grain boundary of the pipes. As a result, the a phase melted partly and the pipes were bonded to the pipes with the base metal metallurgically. Porous Al-Cu alloys with aligned unidirectional pores with porosity of 26% are fabricated by this method.