Rainer Hebert - Research
Our research aims at developing a fundamental understanding of the microstructure evolution of metals and alloys under intense deformation. Competing mechanical and thermally activated processes offer novel microstructure evolution pathways that yield materials with improved properties. In one research area we investigate the effect of deformation on the crystallization behavior of amorphous alloys that represent a new class of materials with exceptional strength, resilience, and often corrosion resistance. We are interested in the effect of deformation on the atomic arrangements in amorphous phases, notably the genesis of nanocrystals, and examine the thermomechanical behavior with different experimental techniques, including but not limited to thermal and thermomechanical analysis, diffraction techniques, and electron microscopy. We use fundamental relaxation and crystallization studies in combination with deformation to devise new synthesis strategies for amorphous and partially devitrified amorphous alloys.

We apply intense deformation in addition to develop bulk nanolaminate materials with improved strength and ductility. Composite materials that combine phases with high strength as well as ductile phases prove most advantageous for structural applications. Dramatic improvements in strength have been observed for multilayers with a nanoscale layer thickness due to changes in the dislocation behavior. Following repeated rolling and folding of elemental multilayers, we induce bulk samples with a nanoscale layer thickness. Our research explores the layer refinement mechanisms and alloying reactions at the layer interfaces. We investigate the combined effects of annealing and deformation on the multilayer microstructure evolution and apply mostly electron microscopy and X-ray diffraction in this research area.

In a separate research field we will examine the actuation behavior of polymer films. Volume changes of polymer films often result from an electrochemically induced cation exchange between the films and their environment. Although polymer actuators have so far mostly been immersed in aqueous electrolyte solutions, our efforts will be directed towards solid-state electrolytes. Building upon our experience with deformation-induced microstructural changes in metallic materials, we will seek to control the solid-state electrolyte microstructure, especially the level of crystallinity, to enhance the cation mobility in the solid-state electrolyte.