Tuesday  |  Milwaukee  |  09:40 AM–10:00 AM

#19460, Stress-Strain Hysteresis in Layered Solids: A Study of Graphite and Ti₃SiC₂

Polycrystalline MAX phase Ti₃SiC₂ and graphite are nanolayered materials that share similar plastic deformation mechanisms, such as kinking and basal slip. Both exhibit a hysteretic stress-strain response, indicating energy dissipation during deformation. However, the exact mechanisms driving this dissipation have been debated. This study investigates the evolution of damage, irrecoverable strain, and energy dissipation as stress increases in moderately oriented Ti₃SiC₂ and isotropic graphite. By comparing these properties, we aim to identify the physical phenomena influencing hysteresis at varying stress levels. Our approach follows the cyclic loading methodology of Benitez et al. (2016) to examine mechanical behavior evolution. Two-dimensional digital image correlation (DIC) was used with two cameras looking at opposite sides of cuboidal specimens (i.e. oriented 180 degrees apart), to average-out spurious strains due to potential out-of-plane motion. Electron backscatter diffraction (EBSD) was performed on pristine and 60% loaded Ti₃SiC₂ to directly investigate kinking. Dictionary indexing of EBSD patterns improved accuracy, with low-angle grain boundaries inferred as likely kink boundaries. For Ti₃SiC₂, the stress-strain behavior stages matched those reported for Ti₂AlC in literature. In graphite, damage contributed to hysteresis over a larger fraction of the stress-strain response. Notably, the fraction of low-angle grain boundaries showed no significant difference between the pristine and 60% loaded Ti₃SiC₂ samples. Accurate EBSD indexing was crucial to confirm the presence of true grain boundaries.

Alexander Westra   Colorado School of Mines
Emily Pittman   Colorado School of Mines
Xingyuan Zhao   Johns Hopkins University
Marc De Graef   Carnegie Mellon University
Leslie Lamberson   Colorado School of Mines