A novel process named Centrifugal Duplex Casting has been proposed: it is a manufacturing process of aluminum cast pipes with in-situ composite layer which contains fine intermetallic compounds. In this process, two kinds of molten metals, i. e. molten aluminum (first melt) and molten Al-Cr alloy with higher liquidus temperature (second melt), are cast in sequence at a given interval in a rotating mold. The second melt collides with the meniscus of the spinning first melt, and is dispersed as fine fluid clumps. These fluid clumps are rapidly quenched, migrate toward the outer periphery, and accumulate to form the composite layer. The intermetallic compounds in this composite layer are much smaller in particle size than the Al-Cr alloy centrifugally cast by the conventional process. The solidification structure of the cast pipe produced by Centrifugal Duplex Casting is controlled by cooling capacity of the first melt. For instance, when the first melt has superheat at the time of the pouring of the second melt, coarse intermetallic particles grow inside of the refined composite layer. On the other hand, when the first melt has partially been solidified, the growth of the particles is suppressed. Therefore, the time interval from first to second pouring is an important parameter in this process.
