Multi-transformations in rapid solidification of highly undercooled hypoeutectic Ni-Ni3B alloy melt

Junfeng Xu, Di Zhang, Feng Liu, Zengyun Jian

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3 Scopus citations

Abstract

The solidification of undercooled Ni-3.3 wt% B alloy was studied by high-speed video analysis and microstructural analysis. For moderate initial undercooling (ΔTp = 75 K), the solidification interface for primary phase transformation manifests a shape of a planar dendrite, and possesses an constant growth velocity, for eutectic transformation whereas the interface presents multi-dendrite shape and spasmodic growth, so that a constant velocity cannot describe the interface exactly. These differences suggest that primary phase solidification is controlled by far-distance diffusion while eutectic solidification by short-distance diffusion. For large initial undercooling (ΔTp = 262 K), a kinds of large white dendrites, which is in fact composed of multiple phases, were found in the microstructure, from inside to outside of which, the eutectic phase changes from dot phases (anomalous structure) to irregular eutectic and then to regular eutectic, indicating that the center of white dendrites may be the nucleation zone of eutectic reaction.

Original languageEnglish
Pages (from-to)3307-3315
Number of pages9
JournalJournal of Materials Research
Volume30
Issue number21
DOIs
StatePublished - 15 Sep 2015

Keywords

  • eutectic
  • growth velocity
  • solidification
  • undercooling

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