| 摘要 |
Previously a number of techniques have been used in order to form single crystal or pre-determined crystallography components and articles. Each one of these techniques has its own particular problems, including susceptibility to error. By utilisation of a bi-crystal experiment to determine melt-back length LM and by consideration of the ingress distance d from potential initiation nucleation points on a perimeter of a seed crystal, it is possible to determine a maximum ingress length d. By ensuring that the maximum ingress length d is less than or equal to a seed crystal diameter R, it is possible to project locus from potential nucleation points C<SUB>1</SUB>, C<SUB>2 </SUB>in terms of potential radii for stray grain propagation. As the seed crystal will have a known crystalline orientation, it will be possible to consider two divergent growth curves of the crystal in terms of the stray grains propagating from the point C<SUB>1</SUB>, C<SUB>2</SUB>. In such circumstances, a connector channel can be provided with a radius r=R/4 in an area between the periphery of the seed and the locus of the stray grain maximum ingress distances d. In situations where it is found d exceeds the crystal radius R, it will be understood that the actual crystal diameter R used may be increased or adjustment made with regard to the melt-back length LM in order to alter the maximum ingress distance d.
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