Characterization of as-deposited and deformed nanocrystalline metals with advanced transmission electron microscopy

Date: 17 May 2019

Venue: UAntwerp, Campus Groenenborger, Room U.408 - Groenenborgerlaan 171 - 2020 Antwerp (Wilrijk) (route: UAntwerpen, Campus Groenenborger)

Time: 11:30 AM - 12:30 PM

Organization / co-organization: EMAT

Short description: Friday Lecture by Gunnar Lumbeeck (EMAT)

Although extensive research has been performed on nanocrystalline (nc) materials, the nanoscale fundamental mechanisms controlling the plastic deformation of this class of materials are still not well understood. Advanced electron microscopy techniques were used to investigate in-situ the deformation mechanisms in Palladium (Pd) and the internal stress build-up in sputtered Nickel (Ni).

Automated Crystal Orientation Mapping (ACOM) TEM was performed on pure freestanding Pd thin films to investigate the effect of a DC current on the GB motion, showing a significant change in grain size, which could be an indication of a controllable grain growth during deposition. This opens up the possibility to further investigate the grain size effect on the deformation mechanisms in nc metals. In-situ tensile deformation experiments were performed to study the dislocation nucleation and motion through the sample. The results show an evolution from intergranular dislocation motion between large grains to intragranular dislocations in small grains, proving once more that the grain size does influence the nature of the activated dislocations in the nanocrystalline regime.

Furthermore, nanocrystalline Ni thin films were deposited under a varying Ar pressure, showing changes in internal stress build-up during deposition. ACOM TEM was used for an in-depth study to show the difference in between the samples based on statistical analysis of the grain size, misorientation distribution, texture, etc.