WEB Combustion Synthesis of High Entropy Alloys thin filmsMonday (24.02.2020) 08:40 - 08:40 Poster Room Part of:
This study presents combustion synthesized High Entropy Alloy (HEA) thin films through physical vapor deposition (PVD). By that, metallic multilayer coatings were produced with different multilayer scales in a total thickness of around 700 m. CrCoFeNi, were selected due to their large negative enthalpy of formation and superior physical and chemical properties. Several stacking sequences of CrNi, CoFe, were deposited onto an as-prepared Ni-Al reactive layer on a Si substrate; afterward, the coatings were removed from the Si substrate to form a free-standing HEA thin film. Two fabrication methods were conducted in comparison: combustion synthesis via spark ignition and thermal treatment via rapid thermal annealing. The propagation velocity and temperature during combustion synthesis were monitored by using a high-speed camera and a pyrometer. The reaction products were then analyzed by means of a scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) to identify the phase transformation and stability related to the layer stacking as well as annealing temperature. The compositional profile and uniformity were measured via EDX analysis with SEM. A spark voltage of 12 V for stacking layers of 30 nm was shown to be sufficient despite the unstable and partial reaction. In the reacted region showed highly textured HEA thin films as seen from XRD patterns. In this research, a new synthesize path for developing HEA thin films is first introduced, and the attempt to optimize a stable reaction through individual metal layers and thickness is demonstrated.