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

• Published in: Nature communications Vol. 11; no. 1; pp. 2367 - 11
• Main Authors: Lee, Subin, Vaid, Aviral, Im, Jiseong, Kim, Bongsoo, Prakash, Arun, Guénolé, Julien, Kiener, Daniel, Bitzek, Erik, Oh, Sang Ho
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.05.2020; Nature Publishing Group; Nature Portfolio
• Subjects: 147/143; 639/301/1023/1026; 639/301/357/1016; 639/301/357/537; 639/301/930/328/2082; Condensed Matter; Cross slip; Dislocation loops; Elastic deformation; Emission; Emissions; Gold; Humanities and Social Sciences; Materials Science; Mechanical properties; multidisciplinary; Nanoindentation; Nanotechnology; Nanowires; Nucleation; Physics; Plastic properties; Plastic zones; Plasticity; Plastics; Science; Science (multidisciplinary); Stress distribution; Transmission electron microscopy
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-15775-y

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. Prismatic dislocation loops (PDLs) form during the elastic-to-plastic transition of a dislocation-free volume under nanoindentation. Here the authors observe the initial plasticity and burst-like emission of PDLs in Au nanowires by in-situ transmission electron microscopy, elucidating fundamental aspects of the formation process.