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.

Methods of fabrication by centrifugal casting for functionally graded materials (FGMs) can be classified into two categories on the basis of the relationship between the process temperature and the liquidus temperature of a master alloy. They are the centrifugal solid-particle method and centrifugal in situ method, which could be carried out at process temperatures lower and higher than the liquidus temperature of the master alloy, respectively. In a previous study, it was found that the microstructures of Al–Al ₃ Ti FGMs fabricated by the centrifugal in situ method processed at 1600 °C were different from those fabricated by the centrifugal solid-particle method processed at 800 °C. Although it is expected that the FGMs fabricated by the centrifugal in situ method processed at approximately the liquidus temperature should show extraordinary microstructures, those microstructures have not been observed. In this study, the microstructures of Al–Al ₃ Ti FGMs fabricated at 1000 °C (centrifugal solid-particle method) and 1200 °C (centrifugal in situ method) were investigated.

Fabrication of Al-Al₃Ti functionally graded materials (FGMs) under the centrifugal force has recently attracted some attention. The controlled compositional gradient of the fabricated FGMs, the low cost of the process, and the good mold filling, are the main advantages of the centrifugal method (CM). Using the conventional CM techniques such as the centrifugal solid-particle method and centrifugal in-situ method, FGMs rings with gradually distributed properties could be achieved. As a more practical choice, the centrifugal mixed-powder method (CMPM) was recently proposed to obtain FGMs containing nano-particles selectively dispersed in the outer surface of the fabricated parts. However, if a control of the particles morphology, compound formulas or sizes, is desired, another CM technique is favored. As a development of CMPM, our novel reaction centrifugal mixed-powder method (RCMPM) has been presented. Using RCMPM, Al‑Al₃Ti/Ti₃Al FGMs with good surface properties and temperature controlled compositional gradient could be achieved. In this short review, this novel method will be discussed in detail and the effect of RCMPM processing temperature on the reinforcement particles morphology, size and distribution through the fabricated samples, will be reviewed.

A number of studies have been carried out to identify the mechanism of grain refinement in cast aluminum alloys by addition of grain refiners containing potent heterogeneous nucleation site particles. Although some mechanisms and theories have been proposed, in this review, the role of heterogeneous nucleation site particles on grain refining performance will be focused. The content of this article is as follows. First, the morphology of Al3Ti particles in the Al–Ti refiners is presented, since the grain refining performance of the Al–Ti refiners is affected by the morphology of the Al3Ti particles. Evaluation methods of lattice matching between heterogeneous nucleation site and crystallized phase are, then, discussed. Since we conclude that M value is potentially applicable to predict the effective heterogeneous nucleation site, M value at elevated temperatures is described. Next, fragmentation behavior of Al3Ti particles caused by deformation of the refiners is presented, because the number density of the Al3Ti heterogeneous nucleation site particles is increased by the fragmentation of Al3Ti particles. At the same time, the morphology of the Al3Ti particles, which affects the grain refining performance, can be changed. The concept of grain refiners with high-symmetry L12 modified (Al1−xMex)3Ti intermetallic compound particles, fabrication method and some results on grain refining performance are also given. Finally, application of heterogeneous nucleation for other fields are described.