Fabrication of lotus-type porous Al-Ti alloys using the continuous casting technique

Porous Al-5mass%Ti alloys were fabricated using a continuous casting technique in a hydrogen atmosphere, and the effects of transfer velocity (V) and the peritectic solidification process on the pore morphology and matrix microstructure were examined. In the case of V = 0.5 mm/min, columnar microstructure and directional pores grow along the transfer direction. The Al₃Ti phases are formed in localized regions of matrix part, and however, they do not suppress the growth of directional pores in the other regions. In the case of 5.0 mm/min, because needle-like Al₃Ti phases grow along the transfer direction, directional pores can grow between them. On the other hand, in the case of 10.0 mm/min, spherical pores surrounded by equiaxed peritectic microstructure and homogeneously distributed Al ₃Ti phases are formed, because the primary α -Al and Al ₃Ti phases probably prevent the growth of directional pores.