Gaining sight after being blind: A tribute to Jing Zhu

Abstract

This contribution to the Festschrift for Professor Jing Zhu concentrates on in-situ electron microscopy, a topic which is key in her scientific work. In particular this paper delineates the possibilities of utilizing in-situ transmission electron microscopy to unravel size effects in the structure-property relationship. We have focused on in-situ compression, tension and cyclic fatigue experiments on non-crystalline metallic materials, also called metallic glasses (MG). In-situ quantitative compression tests revealed intrinsic and strong size effects of taper-free metallic glass nanopillars inside a transmission electron microscope (TEM) on different MG compositions. The deformation is defect-nucleation-controlled in larger pillars but becomes propagation-controlled in smaller pillars. A unique increase in strength and strain hardening was observed for smaller sized specimens in tension which is different compared to compression experiments with the same MG compositions. Under cyclic loading a very interesting new phenomenon was observed of increasing deformability depending on the number of cycles and size. The increase in deformability increases with increasing diameter whereas the number of cycles to reach half of the peak stress is decreasing with increasing diameter. The proposed experimental technique of loading and unloading cycles opens a new route to increase the ductility of metallic glasses.