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Effect of Si on the growth behavior of the Fe2Al5 phase formed at the Al-xSi(liquid)/Fe(solid) interface during holding was investigated by a synchrotron radiation real-time imaging technique. Results show that growth of the Fe2Al5 phase is accompanied by its simultaneous dissolution into the melt. Addition of Si inhibits the growth of Fe2Al5 to reduce its thickness and change its morphology. The growth and dissolution kinetics of the Fe2Al5 phase are discussed. [ABSTRACT FROM AUTHOR]

The morphological transition and growth mechanism of Al3Ni phase during solidification at the liquid Al/solid Ni interface was investigated through synchrotron radiography. The remelted peritectic Al3Ni is dominated by coalescence of adjacent grains and precipitation with the morphology changing from columnar, irregular, scallop type to faceted shape. The hollow proeutectic Al3Ni is formed on a solid base. The increased r/R ratio and steep variation lead to the change from regular to irregular hollowness with asymmetrical shape. [ABSTRACT FROM AUTHOR]

Synchrotron X-ray radiography was utilized to in situ study the Ni dissolution during holding and growth behavior of intermetallic compounds (IMCs) during solidification at the liquid Al/solid Ni interface, and synchrotron tomography was used to reconstruct the diversified Al3Ni phases. The dissolution and IMC growth was quantitatively analyzed. During holding, the solid Ni dissolved heterogeneously into liquid Al, and the quantification of Ni concentration was obtained from intensity values. The layered Al3Ni2 formed at the interface during solidification, following by columnar and needle-like Al3Ni. The growth of Al3Ni2 layer followed a parabolic law, being controlled by bulk diffusion mechanism. The peritectic and proeutectic Al3Ni grew along the length obviously at the early stage and coarsened in the late stage. The proeutectic Al3Ni phase had a stronger [001] orientation than peritectic Al3Ni phase. [ABSTRACT FROM AUTHOR]

NaZn-type La(Fe,Si) alloy is a promising magnetocaloric material for solid refrigeration. Currently, several days of high-temperature annealing are typically required to transform both the α-Fe phase and LaFeSi phase to a La(Fe,Si) phase by diffusion. However, no bulk casting has yet been reported. In this study, directional solidification is used to prepare LaFeSi alloys with a dual-phase microstructure consisting of α-Fe and LaFeSi phases. It was found that the volume fraction of La(Fe,Si) phase in directionally solidified LaFeSi alloys can be increased to ~62 pct. It was also found that the volume fraction of the La(Fe,Si) phase is dependent primarily on the temperature gradient at different growth rates, which can be the result of their wide temperature range between solidus and liquidus. A significant Si segregation was observed in directionally solidified LaFeSi alloys. Furthermore, the solidification path was discussed, focusing on the volume fraction increase of the La(Fe,Si) phase by directional solidification. [ABSTRACT FROM AUTHOR]