Experimental Analysis of Slip Systems Activation in Neutron-Irradiated Zirconium Alloys and Comparison with Polycrystalline Model Simulations

Abstract

The deformation mechanisms of recrystallized zirconium alloys are strongly influenced by neutron irradiation with significant consequences on the mechanical behavior at the macroscopic scale. It is especially observed, through transmission electron microscopy, that the dislocation channeling process in the basal plane is the main deformation mechanism after irradiation. A polycrystalline modeling which takes into account both the specific post-irradiation deformation mechanisms, and the texture of the material has been developed. This physically based model reproduces the mechanical behavior of the material for both monotonic and cyclic tests. The slip system activities have been computed for several grains observed by TEM. The activation of the basal slip is very well predicted. Moreover, the activation of hc+ai-pyramidal slip observed only in few grains, and the absence of prismatic activation is also well predicted showing the reliability of the modeling.

Plastic relaxation and solute segregation to β-Nb second phase particles in Zr-Nb alloys: A discrete dislocation plasticity study

“…The plane of the simulation is the α-Zr hcp basal plane, and we assume that the prism slip systems are the only ones that are activated. This is the case for unirradiated Zr, whereas basal slip is most active in irradiated Zr [41,42]. The prism slip system consists of three families of slip planes, corresponding to the three possible Burgers vectors of the a -type, spaced by an angle of 120°.…”

“…After irradiation, the slip behaviour of the material should change, due to the creation of a high density of small a -type dislocation loops [41]. This would be difficult to include in the simulations.…”

Mechanism-based modeling of solute strengthening: Application to thermal creep in Zr alloy

“…Pyramidal <c+a> slip can also be activated but with critical stress 10 to 20 times higher than the prismatic slip. Besides, pyramidal <a> is also considered in the simulations since cross-slip of screw segment from prismatic plane to pyramidal <a> and basal planes has been reported for Zr alloys (Caillard et al, 2015;Onimus et al, 2013).   1012 tensile twinning and   1122 compressive twinning are excluded from this work as their activations are suppressed at elevated temperatures (Beyerlein and Tomé , 2008;Kanitpanyacharoen et al, 2012).…”

Strain localization and failure in irradiated zircaloy with crystal plasticity

“…The hypotheses have been developed on the basis that softening primarily affects the basal systems, as widely reported in the literature, but in addition the effects of secondary softening mechanisms such as that occurring on prismatic systems (as opposed to pyramidal systems) are also then considered [2,3,5,6] and indeed are then subsequently argued to be essential in order to capture experimentally observed strain localization and failure.…”

“…3, is observed in irradiated zircaloys compared to unirradiated samples [3][4][5][6]. This has been attributed to the efficient clearing of dislocation channels leading to increased slip activity along these channels [4].…”