Evidence for the transition from primary to peritectic phase growth during solidification of undercooled Ni-Zr alloy levitated by electromagnetic field.

P Lü,K Zhou,H P Wang

doi:10.1038/srep39042

P Lü, K Zhou + Show 1 more

Open Access

https://doi.org/10.1038/srep39042

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Journal: Scientific Reports	Publication Date: Dec 1, 2016
Citations: 15	License type: CC BY 4.0

Affiliation: Northwestern Polytechnical University

Abstract

The Ni83.25Zr16.75 peritectic alloy was undercooled by electromagnetic levitation method up to 198 K. The measured dendritic growth velocity shows a steep acceleration at a critical undercooling of ΔTcrit = 124 K, which provides an evidence of the transition of the primary growth mode from Ni7Zr2 phase to peritectic phase Ni5Zr. This is ascertained by combining the temperature-time profile and the evolution of the solidified microstructures. Below the critical undercooling, the solidified microstructure is composed of coarse Ni7Zr2 dendrites, peritectic phase Ni5Zr and eutectic structure. However, beyond the critical undercooling, only a small amount of Ni7Zr2 phase appears in the solidified microstructure. The dendritic growth mechanism of Ni7Zr2 phase is mainly governed by solute diffusion. While, the dendritic growth mechanism of Ni5Zr phase is mainly controlled by thermal diffusion and liquid-solid interface atomic attachment kinetics.

Highlights

IntroductionThe solidification behavior for this type of peritectic alloy is complicated and considerably important for deep and comprehensive understanding of peritectic solidification under highly undercooled condition
The dendritic growth mechanism of Ni7Zr2 phase is mainly governed by solute diffusion
Thermal diffusion and liquid-solid interface atomic attachment kinetics play a vital role in determining the growth velocity of Ni5Zr phase

Summary

Introduction

The solidification behavior for this type of peritectic alloy is complicated and considerably important for deep and comprehensive understanding of peritectic solidification under highly undercooled condition. The objective of this work is to investigate the transition of the primary growth mode from Ni7Zr2 phase to peritectic phase Ni5Zr during the solidification of undercooled Ni83.25Zr16.75 peritectic alloy by the measured dendritic growth velocity and solidified microstructures. The dendritic growth kinetics of Ni7Zr2 phase and Ni5Zr phase is studied to reveal the evolution of solidified microstructure

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