Pulsed Metallurgy for 2-Dimensional Structuring of Metallic Thin Films and Surfaces

• Applicant: Dr.-Ing. Karsten Woll
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 325754192

• Final Report Year: 2023

Final Report Abstract

The Emmy-Noether Group „Pulsed Metallurgy“ explores pathways for metallic thin films that enable microstructure tuning for interesting mechanical properties. Al/Ni multilayer is the model material system. The current project expands pulsed metallurgy for 2-dimensional structuring of thin films and surfaces. We apply a heat sink with cavity to create a temperature hot spot on the surface. For the first time, we show the success of this approach and present results that characterize the local microstructure development of the thin film in the hot spot region. A method has been developed to characterize phase transformations in the hot spot. In detail, we developed a structuring experiment where the thin film is globally resistively heated while the electrical resistance is recorded locally in the hot spot via a four-point-setup. Increases or even steps in the resistance with temperature indicates intermixing or phase transformations, respectively. Correlations with the underlying microstructure changes can only be made indirectly via comparison with resistance signals recorded in a so called analysis experiment. The latter uses the spiral heater approach to heat up the thin film – however, without heat sink. This comparison allows us to conclude that the hot spot temperature was around 350 °C and a first phase transformation was induced. Microstructure analysis in the transmission or scanning electron microscope corroborate this conclusion. The mechanical characterization of pulsed films further shows that the used thermal protocols result in a doubled hardness (depending on the maximal temperature). The latter development can be harnessed in the property tuning of thin films through 2-dimensional structuring.

Publications

• Heterogeneous microstructures tuned in a high throughput architecture. Materials & Design, 229, 111834.
  Short, M.; Müller, J.; Lee, S.; Fornasier, H.; Köhler, U.; Ott, V.; Stüber, M.; Gerdes, B.; Rupp, T.; Kirchlechner, C. & Woll, K.