PhD defense of Albert Zelenika

Albert Zelenika, a PhD student from SOLID, will have his thesis defense on 9th September from 13:00. The topic is "Pattern initiation in plastically deformed metals".

Main supervisor is Henning Friis Poulsen, and co-supervisors are Grethe Winther, Can Yildirim and Carsten Detlefs.

Abstract for the thesis: 

This research sheds light on how metals deform and strengthen when they are stretched or compressed. When metals are deformed, tiny imperfections called dislocations move around within their crystal structure. These dislocations can arrange themselves into patterns that help the metal become harder and more resistant to further deformation.

By using advanced X-ray imaging techniques, it was possible to observe these dislocations in aluminum crystals as they were stretched. Even at very low levels of deformation it was found that dislocations start to form into tiny cell-like structures. These cells begin to appear randomly, they grow in size and number as the strain increases.

In some configurations, the dislocations align into well-defined structures known as geometrically necessary boundaries. These boundaries help the metal  accommodate the deformation and distribute forces more evenly. It was noticed that these boundaries start forming early in the deformation process, even if they are not fully developed at first. The study shows that the organization of dislocations is not entirely predictable but follows certain statistical patterns. This randomness is important because it affects how the metal hardens. The ability to see these dislocation structures in three dimensions provides new insights into how metals strengthen under load.

Understanding these early stages of dislocation patterning is crucial for designing stronger metals and alloys. It helps engineers and scientists create materials that can withstand greater forces without breaking, which is essential for everything from building construction to manufacturing durable products, and the aerospace industry.