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

TL;DR

This study uses a modified DCDC test to observe how dislocations affect crack propagation in MgO ceramics, combining experiments and modeling to enhance understanding of fracture resistance in ceramics.

Contribution

It introduces a novel experimental setup for in situ observation of crack-dislocation interactions and combines it with modeling to provide mechanistic insights.

Findings

Cracks slow down significantly in dislocation-rich regions.

Crack reacceleration occurs after leaving dislocation barriers.

Experiment and simulation results are in strong agreement.

Abstract

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. MgO specimens, furnished with dislocation-rich barriers, were employed to study how dislocations influence crack propagation. 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. Coupled phase field and crystal plasticity modeling replicates the experimental observations and provides mechanistic insight into crack tip - dislocation interactions. The aligned experiment and simulation results underscore the robustness of the technique and its potential to inform the design of more fracture-resistant ceramics via dislocations.