Characterization of a functionally graded directionally solidified Al-33Cu alloy

Abstract

To produce a functionally graded and directionally solidified (FGDS) structure, an Al-33Cu eutectic alloy has been centrifugally cast into a bar-shaped steel mold using a vacuum centrifugal casting system. Uni-dimensional cooling was performed to obtain directional solidification. Microstructural characterizations were carried out on the longitudinally sectioned cast bar along the solidification direction. Results showed that the Al2Cu eutectic lamellar spacing varied between 0.32 µm and 1 µm from the outer region to the inner region of the cast bars along a 75 mm distance. Centrifugal casting has resulted in microsegregation of copper concentration in a range between 55.8 % and 53.9 % from the outer region to the inner region, respectively. Similarly, the volume fraction of the Al2Cu eutectic has also varied between 45.3 % and 53.7 %. This leads to a significant variation in the hardness of the FGDS Al-33Cu eutectic alloy from 183 HB to 155 HB from the outer region towards the inner region.