(181h) Extracting Solid-Melt Interfacial Free Energy and Anisotropy Strength of Al-Cu Alloy Using Molecular Dynamics Simulations

Laser Melt Deposition is one of the growing additive manufacturing techniques employed in industries for creating new and improved materials. During this process, rapid solidification of the melt 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 throw light on crystal growth & crack propagation during these rapid solidification operations. We have tried to analyze the role of undercooling and solute composition on interfacial free energy for an Al-Cu system using molecular dynamics and the capillary fluctuation method.

An Al-Cu phase diagram was first generated for the interatomic potential in use. Crystal-melt interfaces were then created for different undercooling regimes using molecular dynamics, equipped with the solute composition information from the phase diagram. The equilibrium crystal-melt interfaces are then analyzed using the capillary fluctuation method to obtain the interfacial free energy and its anisotropy parameters. Our results show that the interfacial energy for the binary Al-Cu system does not have a linear dependence with solute composition or the amount of undercooling. The results also correctly predict the transition of dendrite growth orientations from (100) to (110) with Cu doping.

Acknowledgments: 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 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.