Array Ordering in Dendritic Crystals and the Influence on Crystal Perfection

Published

December 1, 2004

Author(s)

R E. Napolitano, David R. Black

Abstract

In the work reported here, several important issues regarding the role of the evolving dendritic structure in the generation of crystal defects are investigated. Industrially produced single-crystal castings are examined, and the dendritic arrays are characterized using aminimum spanning tree (MST) graph analysis. Crystallographic perfection and associated defect structures are characterized independently using x-ray topography and compared with the dendritic microstructure and quantitative descriptors of array order. It is observed that, the dendritic array structure evolves substantially over a growth length of 25 millimeters while themosaic nature of the crystal remains relatively constant. In addition, the minimum spanning treegraph construction is applied both globally and locally to the primary dendritic array. The utility of the MST edge-length mean and standard deviation parameters are evaluated and determined to be rather insensitive to differences in the local order observed in the dendritic array. The statistical sample size dependence of the minimum spanning tree is evaluated with respect to its utility in distinguishing between square and hexagonal order, with varying degrees of superposed random noise.

Citation

Journal of Materials Science

Volume

39

Issue

No. 23

Pub Type

Journals

Keywords

dendrite orientation, dendritic crystals, microstructure, superalloy, x-ray topography

Citation

Napolitano, R. and Black, D. (2004), Array Ordering in Dendritic Crystals and the Influence on Crystal Perfection, Journal of Materials Science (Accessed April 25, 2024)