Extracting Anisotropy Strength and Interfacial Free Energy of Al-Cu Alloy under Rapid Cooling Conditions Using Molecular Dynamics Simulations

Laser Melt Deposition is one of the growing additive manufacturing techniques employed in industries for creating new and improved materials. Rapid solidification of the melt during this process has been known to form cracks for an Al-Cu system. These cracks impede the overall strength of the material. Understanding the changes in interfacial free energy can help shed light on crystal growth & crack propagation during these rapid solidification operations. Using molecular dynamics and capillary fluctuation method we have tried to analyze the role of undercooling and solute composition on interfacial free energy for an Al-Cu alloy system.<br/><br/>An Al-Cu phase diagram was first generated for the interatomic potential in use. This was done by analyzing the solidus and liquidus compositions at equilibrium. With the solute composition information from the phase diagram, crystal-melt interfaces were created using molecular dynamics. The interfaces were created along different crystallographic directions and at various temperatures. The rough interfaces were then analyzed using the capillary fluctuation method to obtain the interfacial free energy and its anisotropy strength. Finally, the composition-dependent anisotropy can help better predict dendritic growth directions under various undercooling conditions.<br/><br/><b>Acknowledgments:</b> The work is supported by ARL Grant No. W911NF-2020032 and used the Extreme Science and Engineering Discovery Environment (XSEDE) TACC at the stampede2 through allocation [TGDMR140131]. This work utilized resources from the University of<br/>Colorado Boulder Research Computing Group, which is supported by the National Science Foundation (awards ACI-1532235 and ACI-1532236), the University of Colorado Boulder, and Colorado.