Al-40% Cu hypereutectic alloy samples were successfully directionally solidified at a growth rate of 10 mu m/s in different sizes (4 mm, 1.8 mm, and 0.45 min thickness in transverse section). Using the serial sectioning technique, the three-dimensional (3D) microstructures of the primary inter metallic Al2Cu phase of the alloy can be observed with various growth patterns, L-shape, E-shape, and regular rectangular shape with respect to growth orientations of the (110) and (310) plane. The L-shape and regular rectangular shape of Al2Cu phase are bounded by (1101 facets. When the sample size was reduced from 4 min to 0.45 mm, the solidified microstructures changed from multi-layer dendrites to single-layer dendrite along the growth direction, and then the orientation texture was at the plane (310). The growth mechanism for the regular faceted intermetallic Al2Cu at different sample sizes was interpreted by the oriented attachment mechanism (OA). The experimental results showed that the directionally solidified Al-40% Cu alloy sample in a much smaller size can achieve a well-aligned morphology with a specific growth texture. (C) 2014 Elsevier B.V. All rights reserved.