Solidified structure near the ingot surface is complex and it is difficult to analyze the crystallographic orientation by the solidified structure. The reason of complexity is that the growth direction of dendrite does not agree with the plane for observation. Thus thick lines called ghost lines are often observed. The ghost lines have been characterized in this study.
Simplifying the shape of dendrite, the ratio of widths of ghost lines (=γ) has been formulated and the change of γ in orientation of dendrite have been analyzed. It has been found that the angles of ghost lines (η and ξ) as well as γ are the important factors to characterize the solidified structure. In order to determine the spatial orientation of dendrite (θ, φ and β) from η, ξ and γ, the computer program had been developed. Applying this computation method, the solidified structure has been compared with the cross sections of dendrite model. The cross sections obtained by 3D-CAD agreed quite well to the real solidified pattern.
