Stable crack propagation in dislocation-engineered oxide visualized by double cleavage drilled compression test

Understanding crack tip – dislocation interaction is critical for improving the fracture resistance of semi-brittle materials like room-temperature plastically deformable ceramics. Here, we use a modified double cleavage drilled compression (DCDC) specimen geometry, which facilitates stable crack propagation, to achieve in situ observation of crack tip – dislocation interaction inside a scanning electron microscope. Single-crystal magnesium oxide specimens, furnished with dislocation-rich barriers across the intended crack path, were employed to study how localized dislocation structures influence crack dynamics. While individual dislocation behavior could not be resolved due to mechanical drift limitations, crack progression was clearly observed to decelerate within dislocation-rich regions, slowing to 15% of its velocity as compared to the pristine crystal. Upon exiting these regions, cracks reaccelerated until reaching the next dislocation-rich barrier. Complementary phase field modeling coupled with crystal plasticity has been employed to replicate the experimental observations and provide mechanistic insight into crack tip – dislocation interactions, confirming that dislocation-rich zones serve as effective barriers to crack propagation. The aligned experiment and simulation results underscore the robustness of the technique and its potential to inform the design of more fracture-resistant ceramic materials.