In-situ observation of the initiation of plasticity by nucleation of prismatic dislocation loops

Subin Lee , Aviral Vaid (1) , Jiseong Im , Bongsoo Kim , Arun Prakash (1) , Julien Guénolé (1) , Daniel Kiener (2) , Erik Bitzek (1) , Sang Ho Oh

1 Department of Materials Science and Engineering, Institute I, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU)
2 MUL - Montanuniversität Leoben

The elastic-to-plastic transition during the deformation of a dislocation-free nanoscale volume is accompanied by displacement bursts associated with dislocation nucleation. The dislocations that nucleate during the so-called "pop-in" burst take the form of prismatic dislocation loops (PDLs) and exhibit characteristic burst-like emission and plastic recovery. Here, we report the in-situ transmission electron microscopy (TEM) observation of the initial plasticity ensued by burst-like emission of PDLs on nanoindentation of dislocation-free Au nanowires. The in-situ TEM nanoindentation showed that the nucleation and subsequent cross slip of shear loop(s) are the rate-limiting steps. As the indentation size increases, the cross slip of shear loop becomes favored, resulting in a transition from PDLs to open half-loops to helical dislocations. In the present case of nanoindentation of dislocation-free volumes, the PDLs glide out of the indentation stress field while spreading the plastic zone, as opposed to the underlying assumption of the Nix-Gao model.

Domaines: Physique [physics]; Science des matériaux [cond-mat.mtrl-sci]

Subin Lee, Aviral Vaid, Jiseong Im, Bongsoo Kim, Arun Prakash, et al.. In-situ observation of the initiation of plasticity by nucleation of prismatic dislocation loops. Nature Communications, 2020, ⟨10.1038/s41467-020-15775-y⟩. ⟨hal-02571135⟩