Zirconium is a metal with a hexagonal close-packed structure. Plasticity in those metals is usually controlled by glide of target='_blank' dislocations, i.e. dislocations with 1/3 Burgers vector glide. Nevertheless, such dislocations do not accommodate deformation in the direction, for which twinning or glide of dislocation need to be activated. The aim of this work is to understand the dislocation glide based on an both experimental and a numerical approach.
Post-mortem TEM observations on Zr alloys strained to 2% at 350°C have been realized. The glide plane of all observed dislocations is a first order pyramidal plane, in agreement with the literature. Dislocations are aligned in a preferential orientation corresponding to the intersection of the pyramidal plane and the basal plane, thus leading to an almost edge character for these straight dislocations. In situ TEM tensile tests at room temperature have been then performed to understand the glide mechanism of these dislocations.
In order to study the core properties of dislocations, atomic simulations relying on empirical potentials have been used. The potentials have been selected by comparing the obtained stacking faults in all possible glide planes with ab initio results. The core structure of the screw dislocation has then been modeled with two potentials. One potential leads to non-planar dislocation cores dissociated in two different planes, while the other predicts planar cores dissociated in a single plane, with the most stable configuration obtained for a dissociation in a first order pyramidal plane. As TEM observations did not show any lattice frictions for the screw character, non-planar cores appear as an artifact of the empirical potential and the potential leading to a planar dissociation in a first order pyramidal plane is preferred to simulate the glide of dislocations with molecular dynamics.
