Date of Award
December 2020
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
Committee Member
Fadi FA Abdeljawad
Committee Member
Huijuan HZ Zhao
Committee Member
Garrett GP Pataky
Committee Member
Marian MK Kennedy
Abstract
High Entropy alloys (HEAs) are metal alloys consisting of multiple base metals in equimolar or near equimolar concentrations. HEAs exhibit unique combinations of properties that render them an attractive choice in many engineering applications. Among HEAs, a single phase face centered cubic (FCC) CoCrFeMnNi alloy, known as the Cantor alloy, shows simultaneous strength and ductility specifically at cryogenic temperatures. This has been attributed to the activation of deformation twinning as an additional mode of plastic deformation. Experimentally it has been observed that grain boundaries (GBs) facilitate the nucleation of deformation twins in HEAs. However, the role of GB geometry in the deformation behavior of HEAs remains unexplored. In this thesis work, we leverage atomistic simulations to systematically investigate the role of GB geometry in the deformation behavior of the Cantor alloy at 77 K. To this end, a series of Cantor alloy bicrystals with <110> and <111> symmetric twist GBs are constructed and used in tensile deformation simulations. Simulation results reveal that plastic deformation proceeds by the nucleation of partial dislocations from GBs, which then grow with further loading by bowing into the bulk crystals leaving behind stacking faults. Variations in the nucleation stress exist as function of GB character, defined in this work by the twist angle. Our results provide future avenues to explore GBs as a microstructure design tool to develop HEAs with tailored mechanical properties.
Recommended Citation
Lee, Hyunsoo, "The Role of Grain Boundaries in the Tensile Deformation Behavior of CoCrFeMnNi High Entropy Alloys" (2020). All Theses. 3472.
https://tigerprints.clemson.edu/all_theses/3472