Abstract
We have two visitors who will introduce us to their work at the Montanuniversitaet Leoben University (Austria).
Installation and capabilities of a high-end analytical scanning transmission electron microscope *Dr. Thomas M. Kremmer
*Chair for Nonferrous Metallurgy, Montanuniversitaet Leoben, Austria, thomas.kremmer@unileoben.ac.at
Understanding of material physics and its relation to the microstructure is necessary in order to improve the properties of advanced materials. Characterizing this relationship between the production, structure and final properties of materials can only be achieved via the use of the latest imaging and analytical techniques in combination with a high expertise in materials engineering. For this purpose a modern “Analytical Scanning Transmission Electron Microscope” was newly acquired from Thermofischer Scientific (Talos F200X).
This talk is dedicated to both the installation and capabilities of the new research infrastructure. In the first part, an overview of the installation and the necessary room adaptions to obtain excellent imaging conditions for TEM-work will be provided. This includes our setup for vibration dampening, air conditioning, electromagnetic field cancellation and common pitfalls in these areas during the planning stage. The second part focuses on obtained results in the areas of aluminium alloy development (especially precipitation of hardening phases) and radiation tolerant materials. Additionally, the possibilities for in-situ experiments (cooling, heating with MEMS-holder, 3d tomography) will be highlighted.
Phase Transitions in Quenched Metallic Systems Prof. Stefan Pogatscher*
*Distinguished Professor for Materials Engineering of Aluminum, Chair of Nonferrous Metallurgy, Montanuniversitaet Leoben, Austria, stefan.pogatscher@unileoben.ac.at
Nearly all classes of materials show non-equilibrium phase transitions and the first technological use of quenching metals for designing properties is documented as ~800 BC. However, the decomposition process towards equilibrium is still difficult to understand due to the strong non-equilibrium kinetics. Two examples are discussed: First the decomposition of a quenched super saturated solid solution and second the decomposition of a quenched metallic melt. In the first example the most frequently used group of precipitation hardened aluminum alloys – the AlMgSi alloys – is addressed. In these alloys natural aging affects the formability and the paint bake response for the use in automotive applications. Solute clustering upon natural aging, its implications on industrial aging treatments and the effect of trace elements are discussed. It is shown which physical pre-requisites need to be fulfilled to examine a “diffusion on demand” concept to modify clustering and precipitation kinetics by orders of magnitude. In the second example the discovery of the first solid–solid transition via melting in a metal, detected in the decomposition of a metallic glass, is demonstrated. The transformation path is discussed under its thermodynamic and kinetic prerequisites. Also the capabilities of the applied technique of fast scanning chip calorimetry are addressed. Finally, it is outlined how this novel method links the two examples via its potential for in-situ characterization of phase transitions upon rapid heating and cooling of small-scaled samples.
