Rheology of Earth Materials :

Closing the gap between timescales in the laboratory and in the mantle

25 May 2021 - New publication in Acta Materialia

Dislocation electron tomography, the helpful technique to reveal the complex dislocation microstructure of a Zr irradiated alloy

 

Cladding tubes used in nuclear reactors sustain deformation due to the association of loading and irradiation (Holt 2008). Thanks to dislocation electron tomography (Barnard et al., 2006), the comparison between the microstructure of a deformed Zr specimen and the microstructure of the same kind of specimen followed by ion irradiation reveals a climb mechanism.

The dislocation microstructure of the non-irradiated specimen is not very far from screw configurations, while the microstructure of the irradiated specimen is complex with dislocation loops, wavy dislocations and interactions.

 

Habit planes of loops could be precisely characterized using tomography. The 3D study enables to verify the “butterfly-wing” distribution of the stereographic projection along the [0001] direction (Kelly & Blake, 1973)

            Dislocation interactions are easily deciphered with dislocation electron tomography. Two sessile  dislocation loops in pure climb configurations interact with a   dislocation that moves by climb. As the Burgers vectors of the two junctions are , the junctions are not visible since tomography is performed with the 1-100 diffraction vector. It is worth noting a high ellipticity of the loops along the [0001] direction.

References:

- R.A. Holt, In-reactor deformation of cold-worked Zr-2.5Nb pressure tubes, J. Nucl. Mater., 372 (2-3) (Jan. 2008), pp. 182-214, doi:10.1016/j.jnucmat.2007.02.017.

- J.S. Barnard, J. sharp, J.R. tong, P.A. Midgley, High-Resolution Three-Dimensional Imaging of Dislocations, science, 313 (5785) (Jul. 2006), p. 319, doi:10.1126/science.1125783.

- P.M. Kelly, R.G. Blake, The characterization of dislocation loops in neutron irradiated zirconium, Philos. Mag., 28 (2) (Aug. 1973), pp. 415-426, doi:10.1080/1478437308217463.

 

To learn more:

A. Mussi, A. Addad, F. Onimus (2021) Dislocation electron tomography: a technique to characterize the dislocation microstructure evolution in zirconium alloys under irradiation, Acta Materialia, 213, 116964.  https://doi.org/10.1016/j.actamat.2021.116964