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

• Published in: Scientific reports Vol. 6; no. 1; p. 39042
• Main Authors: Lü, P., Zhou, K., Wang, H. P.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.12.2016; Nature Publishing Group
• Subjects: 639/301/1023/1026; 639/301/357/537; Alloy solidification; Dendrites; Electromagnetic fields; Humanities and Social Sciences; Microstructure; multidisciplinary; Science; Temperature effects; Velocity
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep39042

The Ni 83.25 Zr 16.75 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 Δ T crit  = 124 K, which provides an evidence of the transition of the primary growth mode from Ni 7 Zr 2 phase to peritectic phase Ni 5 Zr. 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 Ni 7 Zr 2 dendrites, peritectic phase Ni 5 Zr and eutectic structure. However, beyond the critical undercooling, only a small amount of Ni 7 Zr 2 phase appears in the solidified microstructure. The dendritic growth mechanism of Ni 7 Zr 2 phase is mainly governed by solute diffusion. While, the dendritic growth mechanism of Ni 5 Zr phase is mainly controlled by thermal diffusion and liquid-solid interface atomic attachment kinetics.