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MM: Fachverband Metall- und Materialphysik

MM 62: Topical session: X-ray and neutron scattering in materials science IV - High Energy Single Grain Diffraction

MM 62.3: Talk

Thursday, April 3, 2014, 18:15–18:30, BAR 205

Diffusion brazing of γ-TiAl alloys: Investigations of the joint by electron microscopy and XRD — •Katja Hauschildt, Andreas Stark, Uwe Lorenz, Norbert Schell, Florian Pyczak, and Martin Müller — Helmholtz-Zentrum Geesthacht, Institut für Werkstoffforschung, Geesthacht, Deutschland

Diffusion brazing is a potential method to repair parts made from TiAl-alloys. In this work the phase constituent and microstructure of the brazed zone for Ni- and Fe-based braze alloys are investigated. For this scanning electron microscopy including energy dispersive X-ray and electron backscattered diffraction were employed. In addition the distribution of phases and changes in lattice parameters in the brazed zone were identified by diffraction with high energy X-rays at the DESY synchrotron in Hamburg, Germany. The braze zone itself is composed of two to three transitional layers reassembling the phase constitution of a TiAl-alloy near the substrate and a microstructure similar to α/β-titanium alloys in the middle of the joint. Besides γ, α₂ and ω, additional phases, which are related to the presence of nickel or iron are also found. The brazed zone microstructure changes significantly during heat treatment, showing that the as-brazed state is far from thermodynamical equilibrium.