The convergence-fault mechanism for low-angle boundary formation in single-crystal castings

被引:139
作者
Napolitano, RE [1 ]
Schaefer, RJ [1 ]
机构
[1] Natl Inst Stand & Technol, Div Met, Gaithersburg, MD 20899 USA
关键词
D O I
10.1023/A:1004747612160
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
A set of nickel-based superalloy single-crystal investment castings was evaluated for crystal perfection. Defect structures near the seed emergence point and other geometric features were examined using X-ray topography. Topographic images were compared with metallographically observed dendritic structures to establish a convergence-fault criterion for the location of low-angle boundaries. To support the phenomenological description of low-angle boundary formation through convergence-faulting, a tip-growth model for simulation of the growth of the dendritic network was developed. This model predicts the local primary growth direction from among three possible [001] directions and identifies regions of convergent growth. A connectivity parameter is defined and used to map the locations where convergence-fault formation is most likely. Predictions are compared with experimental observation. (C) 2000 Kluwer Academic Publishers.
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页码:1641 / 1659
页数:19
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