Mechanical behaviour near grain boundaries of He-implanted UO 2 ceramic polycrystals

Mona Ibrahim (1) , É. Castelier (1) , H. Palancher (1) , Michel Bornert (2) , Sabine Caré (2) , J.-S. Micha (3)

1 CEA Cadarache
2 navier umr 8205 - Laboratoire Navier
3 CEA - Commissariat à l'énergie atomique et aux énergies alternatives

For studying the micromechanical behaviour of UO2 and characterising the intergranular interaction, polycrystals are implanted with helium ions, inducing strains in a thin surface layer. Laue X-ray microdiffraction is used to measure the strain field in this implanted layer with a spatial resolution of about 1 micrometer. It allows a 2D mapping of the strain field in a dozen of grains. These measurements show that the induced strain depends mainly on the crystal orientation, and can be evaluated by a semi-analytical mechanical model. A mechanical interaction of the neighbouring grains has also been evidenced near the grain boundaries, which has been well reproduced by a finite element model. This interaction is shown to increase with the implantation energy (i.e. the implantation depth): it can be neglected at low implantation energy (60 keV), but not at higher energy (500 keV).

Keywords: Mechanical analysis; 2D strain mapping; X-ray micro-diffraction; Light ion implantation; Stress singularity; Polycrystal

Domains: Mechanics of materials [physics.class-ph]

Mona Ibrahim, É. Castelier, H. Palancher, Michel Bornert, Sabine Caré, et al.. Mechanical behaviour near grain boundaries of He-implanted UO 2 ceramic polycrystals. Journal of Nuclear Materials, 2017, 483, pp.13-20. ⟨10.1016/j.jnucmat.2016.10.044⟩. ⟨hal-01711377⟩