Evaluation of three-dimensional orientation of Al3Ti platelet in Al-based functionally graded materials fabricated by a centrifugal casting technique

Al-Al3Ti functionally graded materials (FGMs) are fabricated by a centrifugal casting technique. The Al3Ti particle morphology is observed along three orthogonal planes, i.e. perpendicular to the rotation axis (OP1), perpendicular to the rotation direction (OP2), and perpendicular to the radial direction (the centrifugal force direction) (OP3). The Al3Ti particles are platelet in morphology and their planes are oriented nearly perpendicular to the radial direction. It is found that the orientation of Al3Ti platelets was distributed in the Al-Al3Ti FGMs in a gradually graded manner as well as the volume fraction of Al3Ti platelets. Namely, a larger volume fraction of Al3Ti platelets and a greater orientation of them are observed in the outer region of the ring. Moreover, there is a three-dimensional correlation in the orientation of Al3Ti platelets. Based on geometrical considerations, the orientation of the platelets on one observation plane of the orthogonal planes can be estimated from measurements on a plane perpendicular to the radial direction. The estimated orientation distribution closely agrees with that experimentally observed. Since each Al3Ti platelet-particle has almost the same orientation angle on two different planes, the orientation profiles observed on OP1 are very similar to those along OP2.