Phase Selection and Microstructure Evolution in Nonequilibrium Solidification of Fe40Ni40B20 Alloy |
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Authors: | Ke Zhang Feng Liu Jun-Feng Xu and Gen-Cang Yang |
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Affiliation: | (1) State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, Shaanxi, 710072, P.R. China; |
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Abstract: | Phase selection and microstructure evolution in nonequilibrium solidification of ternary eutectic Fe40Ni40B20 alloy have been studied. It is shown that γ-(Fe, Ni) and (Fe, Ni)3B prevail in all the as-solidified samples. No metastable phase has been found in the deeply undercooled samples. This is
explained as resulting from the size effect of undercooled solidification. At small and medium undercoolings, the dendrite
γ-(Fe, Ni) appears as the leading phase. This is ascribed to the existence of the skewed coupled growth zone in FeNiB alloy.
With increasing undercooling, the amount of dendrites first increases and then decreases, accompanied by a transition from
regular eutectic to anomalous eutectic. The formation mechanisms of the anomalous eutectics are discussed. Two kinds of microstructure
refinement are found with increasing undercooling in a natural or water cooling condition. However, for melts with the same
undercooling, the as-solidified microstructure refines first, and then coarsens with an increasing cooling rate. The experimental
results show that the nanostructure eutectic cell has been obtained in the case of Ga-In alloy bath cooling with an initial
melt undercooling of approximately 50 K (50 °C). |
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