Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 37: Intermetallic Phases II
MM 37.2: Vortrag
Donnerstag, 28. Februar 2008, 10:30–10:45, H 0111
Combined experimental and ab-initio investigation of the physical properties of Ni3Ge and Ni3Al — Markus Dinkel, Rebecca Janisch, •Florian Pyczak, and Mathias Göken — Institute General Materials Properties, University Erlangen-Nürnberg, Erlangen, Germany
Germanium is a promising element for brazing alloys to repair single crystalline ni-base superalloys. Germanium has the advantage that it forms an ordered Ni3Ge phase with the same crystal structure as Ni3Al (γ′ phase). The γ′ phase is responsible for the excellent mechanical properties of ni-base superalloys at high temperature. Interdiffusion between the braze and the base material causes a decreasing concentration of germanium from the brazing zone to the base material and vice versa for aluminum. In the γ′ precipitates germanium is more and more substituted by aluminum, which should lead to changing properties of the γ′ phase between brazing zone center and base material.
In our investigations we determined the chemical composition of binary Ni-Ge by energy dispersive spectroscopy in the electron microscope, the lattice constants using X-ray diffraction investigated the mechanical properties by nanoindentation in an atomic force microscope.
Additionally, equilibrium lattice constants, energies of formation, bulk moduli and defect energies of pure Ni3Ge and Ni3Al phases were calculated by means of a spin-polarized ab initio density-functional method in the general-gradient approximation. The results will be discussed in the light of the experimental data.