Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Casting and Solidification
Effect of ZrO2 on the Heterogeneous Nucleation of γ-Fe Containing 0.75 mass%C
Takashi MorohoshiMasafumi ZezeTooru Matsumiya
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2019 Volume 105 Issue 5 Pages 502-511

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Abstract

The disregistry between β-ZrO2 and γ-Fe is small. In this study, the effect of β-ZrO2 on the nucleation of γ-Fe was investigated by two experiments. First, 20 kg ingots containing 0.75 mass%C with Zr addition or with Al addition were cast and solidification structure was observed. High fraction of equiaxed grain structure was formed in the ingots with Zr addition, but not formed with Al addition. Next, undercooling of 500 g molten steel during cooling was measured. In this experiment a ZrO2 tablet or an Al2O3 tablet was set at the bottom of the crucible. Undercooling with a ZrO2 tablet was smaller than that with an Al2O3 tablet. These two results indicate that β-ZrO2 acts an effective heterogeneous nucleation site for γ-Fe. Interfacial energy differences between liquid Fe and solid γ-Fe both in cases of facing ZrO2 and Al2O3, which are key elements for heterogeneous nucleation capability, were compared and it was found that the difference in the former case is larger than that in the latter case and that chemical contribution is larger in comparison to structural contribution, i.e., lattice misfit energy, in the former case and vice versa in the latter case.

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© 2019 The Iron and Steel Institute of Japan
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