Observing the crack tip behaviour at the nanoscale during fracture of ceramics

TL;DR

This study uses TEM to observe nanoscale crack tip behavior in ceramics, revealing how phase transformation toughening enhances fracture resistance by promoting crack deflection at the atomic level.

Contribution

It provides the first direct nanoscale observations linking phase transformation toughening to increased fracture resistance in ceramics.

Findings

Phase transformation toughening promotes crack deflection at the nanoscale.

Crack resistance increases by approximately 50%.

The work bridges atomistic and continuum fracture models.

Abstract

Ultimately, brittle fracture involves breaking atomic bonds. However, we still lack a clear picture of what happens in the highly deformed region around a moving crack tip. Consequently, we still cannot link nano to atomic-scale phenomena with the macroscopic toughness of materials. The unsolved challenge is to observe the movement of the crack front at the nanoscale while extracting quantitative information. Here we address this challenge by monitoring stable crack growth inside a TEM. Our analysis demonstrates how phase transformation toughening, previously thought to be effective at the microscale and above, promotes crack deflection at the nano-level and increases the fracture resistance by ~50%. The work will help to connect the atomistic and continuous view of fracture in a way that can guide the design of the next generation of strong and tough materials demanded by technologies as diverse as healthcare, energy generation or transport.