Formation mechanism of graded composition in Al-Al2Cu functionally graded materials fabricated by a centrifugal in situ method

To discuss the formation mechanism of the graded composition during the centrifugal in situ method, a detailed study of microstructures in the Al-Al2Cu FGMs fabricated by the centrifugal in situ method from various initial master ingots was carried out. It was found that FGMs can be fabricated by the centrifugal in situ method from not only hypoeutectic or hypereutectic alloys but also eutectic alloys. The particle sizes of the Al2Cu and Al primary crystals were dependent upon their locations in the ring thickness. Using the above experimental results, it has been concluded that the graded structure appearing in the eutectic specimen must be caused by the difference in the densities between Al and Cu in liquid state.