Bulk-scale stress–strain hysteresis in layered crystalline solids: A study of graphite and Ti₃SiC₂

Polycrystalline graphite and the MAX phase Ti₃SiC₂ are layered crystalline solids with similar deformation mechanisms, including basal slip, ripplocation boundaries (RBs), kink boundaries (KBs), and cracking. The interplay of these mechanisms, notably in energy dissipation, has been much discussed in the past twenty-five years. This study builds upon previous work, investigating deformation with a renewed emphasis on the bulk-scale and given recent findings concerning RBs. Our investigation compares the evolution of energy dissipation, nonlinear recoverable and irrecoverable strain, and damage upon increasing stress for graphite and Ti₃SiC₂. Benitez et al.’s (2016) methodology of compressive cyclic loading and post-mortem electron backscatter diffraction (EBSD) to assess the prevalence of kinking based on low-angle grain boundaries (LAGBs) was used. Strains were measured with digital image correlation and EBSD was conducted on Ti₃SiC₂ leveraging dictionary indexing, which was necessary herein to identify LAGBs accurately. The stress–strain stages of Ti₃SiC₂ agree with literature on Ti₂AlC. Damage and energy dissipation were more accelerated in graphite. No significant difference was observed in the fraction of LAGBs between pristine and unloaded Ti₃SiC₂. Trends observed and EBSD evidence that KBs were not dominant suggest that RBs are the primary dissipator of energy in both materials.. Authors: Westra, Alexander G. [Colorado School of Mines, Golden, CO (United States)] (ORCID:000000017277840X); Pittman, Emily R. [Colorado School of Mines, Golden, CO (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000277631009); De Graef, Marc [Carnegie Mellon University, Pittsburgh, PA (United States)] (ORCID:0000000247216226); Zhao, Xingyuan [Colorado School of Mines, Golden, CO (United States); Johns Hopkins University, Baltimore, MD (United States)] (ORCID:0000000196792417); Barsoum, Michel W. [Drexel University, Philadelphia, PA (United States)] (ORCID:0000000178003517). DOE Contract: 89233218CNA000001. Subjects: 36 MATERIALS SCIENCE; Dictionary indexing; Graphite; MAX phase; Ripplocation boundary; Stress–strain response