Fabrication of Al-Cu alloy with elongated pores by continuous casting technique

A1-4.5wt%Cu was unidirectionally solidified by continuous casting technique under hydrogen pressure of 0.1MPa at the transference velocities ranging from 1 to 50 mm|min-1. The fabricated slabs have microstructures of columnar α-dendrite and eutectic, which are typical for hypo-eutectic Al-Cu alloys. Elongated pores are observed in the eutectic region surrounded by several columnar α-dendrites. The shapes of the pores are affected by that of the surrounding α-dendrites. The average pores diameter is several ten μm smaller than the average dendrite arm spacing, which decreases with increasing solidification rate. Therefore, the pore diameter varies from about 200 μm to 30 μm with increasing transference velocity from 1 to 50 mm|min-1. The porosity of the fabricated samples is in the range between 2 ∼ 6 %. There is not significant dependence of the porosity on the transference velocity in the range of the present study. The porosity is similar to the reported value of Al-Si, where the area fraction of eutectic region is smaller than that of α-dendrite.