Molecular Dynamics Study of Atomic Diffusion in Cantor High Entropy Alloy in the Selective Laser Melting Process

Author

Mathew Z. Farias, The University of Texas Rio Grande Valley

Date of Award

12-2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Manufacturing Engineering

First Advisor

Dr. Jianzhi Li

Second Advisor

Dr. Ben Xu

Third Advisor

Dr. Shanshan Zhang

Abstract

High entropy alloys (HEAs) are compositionally complex alloys that are comprised of 5 or more principle elements at near equimolar concentrations. The Selective Laser Melting (SLM) method generally melts pure elemental powders or prefabricated alloy powders, this process allows for the production of heterogeneous structures that would be difficult to create through more conventional means. In-situ alloying in SLM, or Laser Additive Alloying (LAA), using pure elemental powders is a promising means of producing what would otherwise be costly and difficult to fabricate products with less defects using prefabricated powders, therefore this new approach could enable the ability to further tailor alloys and reduce the energy consumption by utilizing the exothermic alloy reaction. However, the effect of the atomic diffusion of elements in the molten pool on the formation of HEA remains poorly understood. In this study, the well-discussed Cantor HEA (Co-Cr-Mn-Ni-Fe) was numerically studied in an in-situ alloying situation, where pure elemental powders (Co, Cr, Mn, Ni, Fe) distributed on a powder bed were melted by a laser, modeled by a moving volume depositing energy, and was subsequently allowed to quench back to the room temperature. The diffusion of specific elements, with respect to their original clusters, was tracked via Mean Square Displacement (MSD) as well as the final composition of key locations. Moreover, Young’s modulus, shear modulus, and lattice thermal conductivity coefficient were simulated and compared with published experimental works. Lastly, the diffusion coefficients were calculated in 3 near-equimolar alloys and 3 alloys with various Fe weight percentages to study the effects of entropy on the tracer diffusion rates. The findings in this study in terms of diffusion behavior can assist the design and manufacturing of other novel HEAs for applications in extreme environment.

Comments

Copyright 2021 Mathew Z. Farias. All Rights Reserve.

https://go.openathens.net/redirector/utrgv.edu?url=https://www.proquest.com/dissertations-theses/molecular-dynamics-study-atomic-diffusion-cantor/docview/2640412917/se-2?accountid=7119

Recommended Citation

Farias, Mathew Z., "Molecular Dynamics Study of Atomic Diffusion in Cantor High Entropy Alloy in the Selective Laser Melting Process" (2021). Theses and Dissertations. 859.
https://scholarworks.utrgv.edu/etd/859