One of the fabrication methods for functionally graded materials (FGMs) is a centrifugal solid-particle method, which is an application of the centrifugal casting technique. However, it is the difficult to fabricate FGMs containing nano-particles by the centrifugal solid-particle method. Recently, we proposed a novel fabrication method, which we have named the centrifugal mixed-powder method, by which we can obtain FGMs containing nano-particles. Using this processing method, Cu-based FGMs containing SiC particles and Al-based FGMs containing TiO2 nano-particles on their surfaces have been fabricated. In this article, the microstructure and mechanical property of Cu/SiC and Al/TiO2 FGMs, fabricated by the centrifugal mixed-powder method are reviewed.

Centrifugal method is often applied as the fabrication process of Functionally Graded Materials (FGMs). This is because that this processing method can fabricate FGMs with large size, easily. However, this processing method has a serious problem, namely it is difficult to disperse particles with small size and low wet ability with matrix. Many of powders with nano or very fine particle size often have attractive attention as functional materials. Therefore the above problem of the centrifugal method should be improved. In this study, we proposed a centrifugal mixed-powder method as novel processing technique for the fabrication of FGM containing nano-particle. On first of this processing, powder mixture of functional nano-particle and matrix material is inserted into rotating mold. After that, matrix ingot is melted in crucible and then the molten matrix is poured into the rotating mold with powder mixture, and then, powder of matrix material will be melted by the heat from molten matrix poured from crucible. Finally, an FGM ring with functional nano-particles distributed on its surface can be obtained. Using this processing method, Al-based FGM containing TiO2 nano-particles on its surface could be fabricated. TiO2 particle has approximately 500nm in diameter. From microstructural observation, it was found that TiO2 particles were successfully distributed on surface of FGM ring. Also, hardness on the surface of the FGM ring was higher than that on inner part due to the dispersion hardening.

Recently, a centrifugal mixed-powder method has been proposed as the processing technique of functionally graded material (FGM) containing fine solid-particles. In this study, Cu-based FGM containing SiC particles was fabricated using this technique. Although the density of SiC is smaller than that of Cu, these SiC particles are successfully distributed on surface of the cylindrical FGM. From this result, it is clear the movement of solid particle in powder mixture during casting is small. Therefore, the gradual distribution of the solid particle can be formed by the control of the volume fraction of solid-particles in powder mixture. Also, it is found that smaller SiC particle can improve the hardness on the surface of the FGMs effectively rather than larger one. In this study, the assignment of the centrifugal mixed-powder method was suggested from the obtained results.

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