Shape of growth cells in directional solidification

Area of Science:

• Materials Science
• Solidification Science
• Crystal Growth

Background:

• Directional solidification is crucial for materials processing.
• Understanding the morphology of growth cells is key to controlling material properties.
• Previous studies often focused on specific aspects of cell shape, lacking a holistic view.

Purpose of the Study:

• To experimentally characterize the complete shape of growth cells in directional solidification.
• To investigate how cell shape evolves with control parameters like pulling velocity, cell spacing, and thermal gradient.
• To establish a comprehensive framework for analyzing growth cell morphology and stability.

Main Methods:

• Building a library of growth cells from directional solidification experiments of a succinonitrile alloy.
• Extracting cell boundaries from images and fitting them using trial functions.
• Analyzing the evolution of fitted parameters with respect to control parameters.

Main Results:

• A coherent evolution of cell shape parameters with control parameters was observed.
• The entire cell shape can be characterized by a single function with two smoothly varying parameters.
• A continuous transition in cell geometry was identified at the cell-to-dendrite transition, refuting distinct solution branches.

Conclusions:

• The study provides a complete characterization of growth cell shapes and their evolution.
• The findings offer a robust framework for validating and refining theoretical and numerical models of solidification.
• This work enhances the understanding of cell stability and morphology in directional solidification processes.