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MM: Fachverband Metall- und Materialphysik

MM 45: Topical Session Heterogeneous Nucleation II

MM 45.1: Vortrag

Freitag, 18. März 2011, 10:30–10:45, IFW B

Grain refinement of TiAl-based alloys: experiments and model calculation — •Daniel Gosslar¹, Robert Günther¹, Christian Hartig¹, Florian Pyczak², Andreas Stark², Ulrike Hecht³, and Rüdiger Bormann¹ — ¹Hamburg University of Technology, Institute of Material Science and Technology, 21073 Hamburg, Germany — ²Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research, 21502 Geesthacht, Germany — ³ACCESS e.V., 52072 Aachen, Germany

Turbine blades of TiAl-based alloys are on the verge of series production. The major advantages of these alloys are their good mechanical properties up to at least 800 °C and the relatively low density. Thereby it becomes possible to replace heavier Ni-based alloys in order to save weight and reduce fuel consumption of aircraft engines. Microstructure refinement of TiAl-based alloys is an important issue of concern. It can be achieved by several distinct ways, depending on alloy composition. One possible way offers particle inoculation of the melt using adequate boron / boride additions. Conventional casting experiments are used to study the effect of boride inoculation on the as cast microstructure. The boride phases are investigated by transmission electron microscopy and synchrotron diffraction experiments. For the first time a metastable monoboride is identified in a high boron containing (> 2 at.% B) Ti-45Al (at.%) alloy. The nucleation potency of this boride is evaluated by the crystallographic model of P.M. Kelly and M.-X. Zhang. The grain size evolution is analyzed using the free growth model of L.A. Greer for heterogeneous nucleation.