Damage-tolerant oxides by imprint of an ultra-high dislocation density

TL;DR

This study demonstrates a simple method to engineer ultra-high dislocation densities in ceramics, significantly enhancing their damage tolerance and toughness by suppressing crack initiation and propagation.

Contribution

It introduces a novel room-temperature dislocation engineering technique in ceramics using Brinell scratching to achieve high dislocation densities and improve damage tolerance.

Findings

Dislocations up to ~10^15 m^-2 were achieved in MgO.

Crack initiation and propagation were suppressed in high-density dislocation zones.

Thermal annealing relieves residual stresses but retains dislocation-induced toughening.

Abstract

Dislocations in ductile ceramics offer the potential for robust mechanical performance while unlocking versatile functional properties. Previous studies have been limited by small volumes with dislocations and/or low dislocation densities in ceramics. Here, we use Brinell ball scratching to create crack-free, large plastic zones, offering a simple and effective method for dislocation engineering at room temperature. Using MgO, we tailor high dislocation densities up to ~10^15 m^-2. We characterize the plastic zones by chemical etching, electron channeling contrast imaging, and scanning transmission electron microscopy, and further demonstrate that crack initiation and propagation in the plastic zones with high-density dislocations can be completely suppressed. The residual stresses in the plastic zones were analyzed using high-resolution electron backscatter diffraction. With the residual stress being subsequently relieved via thermal annealing while retaining the high-density dislocations, we observe the cracks are no longer completely suppressed, but the pure toughening effect of the dislocations remains evident.