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

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 ∼10¹⁵ m⁻². We characterise the plastic zones by chemical etching, electron channelling 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 analysed 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.