In:
Journal of Materials Research, Springer Science and Business Media LLC, Vol. 29, No. 21 ( 2014-11-14), p. 2547-2555
Abstract:
Three-dimensional (3D) morphological evolution and growth mechanisms of primary I-phase particles have been investigated in directionally solidified Al–6Mn–2.5Be (wt%) alloy at a wide range of growth rates (100–1500 μm/s). At relatively low growth rates (100–600 μm/s), the I-phase particles exhibit faceted growth with strong anisotropy, forming a hierarchical flower-like aggregate with icosahedral morphological symmetry composed of several attached irregular polyhedrons or pentagonal dodecahedrons. At higher growth rates (e.g., 1000 μm/s), the interface of the I-phases becomes unstable along the edges and corners of the pentagonal dodecahedron, thereby arousing growth perturbations. Correspondingly, a transition from faceted to nonfaceted growth occurs with increasing growth rate. Further increase of the growth rate leads to the formation of I-phase columnar dendrites' preferential growth along the 3-fold axis. The configurations of the flower-like aggregates can be adequately illustrated by a geometrical model in terms of the perfect and elongated pentagonal dodecahedrons. A growth mechanism for the flower-like aggregates has been proposed based on the clear understanding of the 3D morphological evolution of the I-phase particles.
Type of Medium:
Online Resource
ISSN:
0884-2914
,
2044-5326
DOI:
10.1557/jmr.2014.287
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2014
detail.hit.zdb_id:
54876-5
detail.hit.zdb_id:
2015297-8
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