Papers by Keyword: Gamma TiAl Alloys

Abstract: β solidifying γ titanium aluminide alloys exhibit fine and homogeneous microstructures in the cast condition, in particular if the alloys contain B as a grain refining agent. Following work in the literature [1], it is demonstrated that the grain refining effect due to B is solely attributed in such alloys to its effect on the solid-state β/α transformation. The results further show that grain refinement in these materials can be obtained by a simple heat treatment, even if the microstructure has been extensively coarsened through prior heat-treatment.

Abstract: In view of the development of improved TiAl cast alloys the potential of the  transformation and its dependence on the addition of several alloying elements has been investigated. It was found that microstructural refinement in  solidifying alloys can be attributed to the alloying effect on the kinetics of the  transformation. This also holds for grain refinement through Borides which apparently serve as nucleation sites for the  phase in the solid-state transformation.

Abstract: Gamma titanium aluminide alloys often solidify peritectically and show a coarse, dendritic microstructure, which can lead to unacceptable mechanical properties in the as-cast condition. In view of the development of improved cast alloys, the dependence of the solidifying microstructure on the aluminum content and other alloying elements was investigated. The formation of the observed solidification microstructures is discussed in comparison with microstructure formation maps calculated by the NCU (nucleation and constitutional undercooling) model developed by Hunziker et al. [1].