Place: Departmental Lunch Colloquium of the Department of Materials Science and Engineering, Delft University of Technology, Delft, The Netherlands
Single crystal superalloys are used widely in high-temperature applications. Most commercial superalloys are based on Ni-Al and comprise 10 or more alloying elements. For example, Re and other 5d elements are added to improve creep resistance. Recently, materials based on Co-Al-W were shown to exhibit a γ/γ' microstructure which makes these alloys interesting for singe crystal superalloy applications.
We compare and contrast Co-based and Ni-based alloys by high-throughput densityfunctional theory (DFT) calculations. We relate phase stabilities in Co-X and Ni-X binary systems with X=Al, W, Re and the ternary systems Co-Al-W and Ni-Al-Re. Our DFT results are also used in ab initio CALPHAD calculations. Furthermore, we use a newly parameterised cluster expansion in order to study the solubility of the transition elements W, Mo, Ti, and Ta on the Al sublattice of L12-Co3Al.