Maximal curvature and crystal orientation on directionally solidified dendrites

Area of Science:

• Materials Science
• Crystallography
• Solidification Science

Background:

• Directional solidification of transparent materials often results in crystalline dendritic growth.
• Understanding the relationship between crystal orientation and dendrite morphology is crucial for materials processing.
• Previous studies have explored dendrite growth but lacked precise methods to link curvature maxima to crystallographic directions.

Purpose of the Study:

• To experimentally determine the locations of maximal curvature on crystalline dendrite tips during directional growth.
• To investigate the influence of crystal lattice structure on interface morphology.
• To establish a method for recovering crystal orientations from observed dendrite shapes.

Main Methods:

• Experimental observation of dendrite growth in thin transparent samples.
• Determination of local interface curvatures by analyzing the intersection of nearby interface normals.
• Correlation of curvature maxima with crystallographic orientations.

Main Results:

• Maximal curvature on dendrite tips consistently occurs at a specific interface normal direction.
• This direction is solely determined by the crystal lattice and is independent of growth conditions (e.g., thermal gradient, velocity).
• At high pulling velocities, this direction aligns with the dendrite growth direction.

Conclusions:

• The crystallographic orientation dictates the maximal curvature direction on dendrites, irrespective of external growth parameters.
• This finding provides a novel method to deduce crystal orientations from dendrite morphology.
• It offers insights into how crystal anisotropy influences the formation and orientation of directionally solidified dendrites.