Evolution of stress fields during crack growth and arrest in a brittle-ductile CrN-Cr clamped-cantilever analysed by X-ray nanodiffraction and modelling
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Authors
Organisational units
External Organisational units
- University of Oxford
- Erich Schmid Institute of Materials Science
- ESRF
- Voestalpine Eifeler Vacotec GmbH, Düsseldorf
- University of Udine
- Christian Doppler Laboratory for Advanced Synthesis of Novel Multifunctional Coatings
- Diamond Light Source, Harwell Science and Innovation Campus, Harwell
- Institute of Plasma Physics, Academy of Sciences of the Czech Republic
Abstract
In order to understand the fracture resistance of nanocrystalline thin films, it is necessary to assess nanoscopic multiaxial stress fields accompanying crack growth during irreversible deformation. Here, a clamped cantilever with dimensions of 200 × 23.7 × 40 μm 3 was machined by focused ion beam milling from a thin film composed of four alternating CrN and Cr layers. The cantilever was loaded to 460 mN in two steps and multiaxial strain distributions were determined by in situ cross-sectional X-ray nanodiffraction. Characterization in as-deposited state revealed the depth variation of fibre texture and residual stress across the layers. The in situ experiment indicated a strong influence of the residual stresses on the cross-sectional stress fields evolution and crack arrest capability at the CrN-Cr interface. In detail, an effective negative stress intensity of −5.9 ± 0.4 MPa m ½ arose as a consequence of the residual stress state. Crack growth in the notched Cr layer occurred at a critical stress intensity of 2.8 ± 0.5 MPa m ½. The results were complemented by two-dimensional numerical simulation to gain further insight into the elastic-plastic deformation evolution. The quantitative experimental and modelling results elucidate the stepwise nature of fracture advancement across the alternating brittle and ductile layers and their interfaces.
Details
Original language | English |
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Article number | 109365 |
Number of pages | 16 |
Journal | Materials and Design |
Volume | 2021 |
Issue number | 198 |
DOIs | |
Publication status | E-pub ahead of print - 28 Nov 2020 |