In:
Journal of Materials Research, Springer Science and Business Media LLC, Vol. 22, No. 10 ( 2007-10), p. 2953-2963
Abstract:
Adopting glass fluxing and cyclic superheating, high undercooling up to ∼550 K was achieved in bulk eutectic Ni 78.6 Si 21.4 alloy melt. With increasing undercooling, the as-solidified microstructure shows an interesting evolution, i.e., regular lamellar eutectic, coarse directional dendrite, quasi-spherical dendritic colony, fine directional dendrite, fine quasi-spherical dendritic colony, and superfine anomalous eutectic. In combination with different theories for nucleation and growth, the microstructure evolution was analyzed and described using competitions incorporated in rapid solidification of the bulk undercooled eutectic Ni 78.6 Si 21.4 alloy. For undercooling below and above 180 K, Ni 3 Si, and α-Ni are primarily solidified, respectively. This phase selection can be ascribed to competitive nucleation. As undercooling increases, a transition of the prevalent nucleation mode from site saturation to continuous nucleation was interpreted in terms of competition of nucleation mode. Accordingly, the superfine anomalous eutectic is obtained, due to the substantially increased continuous nucleation rate, i.e., grain refinement occurring at high undercooling (e.g., ∼550 K).
Type of Medium:
Online Resource
ISSN:
0884-2914
,
2044-5326
DOI:
10.1557/JMR.2007.0380
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2007
detail.hit.zdb_id:
54876-5
detail.hit.zdb_id:
2015297-8
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