Four papers published with contributions from the HT-team. Congratulations!

Correlative TEM and ATP reveal the atomic scale character of defect in Co-base superalloy

Earlier this year had been a dynamic and productive time for the team of high-temperature materials, which is a key collaboration partner in the SFB/TR 103. Besides the joining of new members in the group (DK), breakthroughs in the bottle-neck phase (ML) and harvesting phase of on-going PhD work (YME), the highlights are, of course, four papers with contribution from the team has been published in the field-leading journals.


Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

In this research we introduce an approach to combine advanced scanning (SEM) and transmission electron microscopy (TEM) with 3D atom probe tomography (APT), to enable direct investigation of solute segregation phenomena in single crystalline Co-base superalloys. Together with colleagues from the MPIE in Düsseldorf we developed novel approaches for site-specific APT-sample preparation of single crystal defects.


On the diffusive phase transformation mechanism assisted by extended dislocations during creep of a single crystal CoNi-based superalloy

In this research we propose a deformation-induced diffusive phase transformation mechanism in the γ’-phase of a single crystalline CoNi-based superalloy. Shearing events involve the creation and motion of a high density of planar crystal defects. Through correlative electron microscopy and atom probe tomography, we were able to do a structural and 3D-chemical characterization of a superlattice intrinsic stracking fault (SISF) and the leading partial dislocation creating the planar defect. We introduce a model for a new in-plane diffusion mechanism during the formation of the fault upon creep.


Thermophysical and Mechanical Properties of Advanced Single Crystalline Co-base Superalloys

In this work we report on the thermophysical and mechanical properties of newly designed multinary CO-base superalloys including the long-term stability, γ’-solvus temperatures, creep properties and oxidation resistance. Our contribution was a first study on deformation microstructures of compressively creep deformed single crystalline samples.


Early stages of scale formation during oxidation of γ/γ′ strengthened single crystal ternary Co-base superalloy at 900 °C

In this work, the role of two-phase microstructure in a ternary Co-base alloy during oxidation at 900 °C was investigated. Parabolic rate constants for each layer, depending on the progress of oxidation were determined. Nature and distribution of oxide phases present in the three individually grown layers were identified in high-resolution with STEM-EDX and confirmed by XRD. Diffusion fluxes on the internal oxidation front were visualized with STEM-EDX mappings after three different exposure times. Mechanisms leading to the formation of discrete Al2O3 precipitates instead of a protective layer are explained.