Identification of active slip modes in twinned bicrystals of GNS/Cu composite through intragranular misorientation axes analysis

Bicrystals serve as a simplified model system for studying the deformation behavior of polycrystalline materials. In this study, we fabricated graphene nanosheets (GNSs) reinforced copper (Cu) matrix laminated composites using electrophoretic deposition and subsequent vacuum hot-press sintering. Interestingly, the composite exhibited a bicrystal microstructure, with two types of adjacent crystals, i.e., denoted as crystal A (φ1 = 222.06, Φ = 40.54, φ2 = 82.5) and crystal B (φ1 = 141.36, Φ = 43.76, φ2 = 1.94), displaying a twin orientation relationship. To investigate the deformation behavior of the GNS/Cu composite, we conducted interrupted room temperature uniaxial tensile tests combined with Scanning Electron Microscope (SEM) Electron Backscatter Diffraction (EBSD) characterization. To identify the activated slip systems in the composites, we performed trace analysis, applied the Schmid Factor law, analyzed the deformation gradient tensor, and conducted intragranular misorientation axis (IGMA) analysis. The trace analysis revealed that slip systems with high Schmid Factor values were favored during tension. Moreover, the deformation gradient tensor elements of the primary slip systems in the two crystals confirmed the deformation features observed by SEM. However, crystal B exhibited a significant deviation in trace angle. Further IGMA investigation revealed that during tension, some slip systems, which were not favored by the Schmid Factor law, were also activated in crystal B. The activation of these slip systems in crystal B can be attributed to the large deviation in the trace angle. The findings in this work provide valuable insights for exploring the underlying deformation mechanisms in polycrystalline materials.