Pore Morphology of Porous Al-Ti Alloy Fabricated by Continuous Casting in Hydrogen Atmosphere

Abstract

Porous Al-5 mass%Ti alloy was fabricated by unidirectional solidification in hydrogen atmosphere, using a continuous casting technique. The porous Al-Ti alloy was prepared at different transfer (solidification) velocities, and the effect of transfer velocity on the pore morphology was investigated. It was found that the pore shape changes with increasing transfer velocity, while the porosity does not change with increasing transfer velocity. In the case of a low transfer velocity (0.5 mmÁmin À1 ), elongated pores surrounded by the columnar microstructure are formed, which indicates that the pores grow along the solidification direction together with the solid phase. In the case of a middle transfer velocity (5.0 mmÁmin À1 ), elongated pores surrounded by the columnar microstructure and needle or plate-like Al 3 Ti alloys are formed. In the case of a high transfer velocity (10.0 mmÁmin À1 ), spherical pores surrounded by the equiaxed microstructure are formed, because the primary crystals formed in the solidification front prevent the growth of elongated pores. It is suggested that the pore morphology is closely related with the solidification rate.

Strongly Orthotropic Open Cell Porous Metal Structures for Heat Transfer Applications

“…Lotus-type materials can be made from iron, nickel, aluminum, copper, magnesium, cobalt, tungsten, manganese, chromium, beryllium, and their alloys [15,18], but not all fabrication techniques can be applied for each material. Depending on the gas, the gas pressure or the amount of metal compound, a maximum porosity of approximately 55% can be reached [15,17].…”