Microstructure and mechanical properties of intermetallic γ-TiAl alloy alloyed with dysprosium

T. Nazarova, K. Nazarov, S. Sergeev, V. Imayev, R. Imayev


The effect of modify by rare earth metal dysprosium in combination with heat treatment on microstructure and mechanical properties on compression testing of intermetallic β-solidifying γ(TiAl) alloy was studied. The image shows a microstructure of alloy Ti-45Al-6(Nb,Mo)-0,2 B-1Dy, where the observed layer DyAl2-phase and Dy2O3 oxide particles.In the present work, the effect of alloying with dysprosium on microstructure and compression mechanical properties of a β-solidifying γ-TiAl alloy has been studied. For this, ingots of the alloys Ti-45Al-6(Nb,Mo)-0,2B-xDy (at.%) with various additions of dysprosium (x = 0, 0,1 and 1 at.%) were melted. The as-cast alloys were homogenized and then cooled in a furnace. These conditions of the alloys were assumed as the initial cast conditions. Microstructure examination showed that Ti-45Al-6(Nb,Mo)-0,2B and Ti-45Al-6(Nb,Mo)-0,2B-0,1Dy alloys had near lamellar microstructures in the initial conditions. Alloying with 1 at.% of dysprosium caused a change in the microstructure morphology from near lamellar to mixed lamellar-globular one. The appearance of globular γ and α2 grains in the alloy alloyed with 1 at.% of dysprosium resulted in an appreciable refinement of the γ / α2 colonies. It was revealed that the addition of 1 at.% of dysprosium to the Ti-45Al-6(Nb,Mo)-0,2B alloy led to changing the phase composition: along with the basic γ, α2 and β(B2)-phases an additional DyAl2 phase was detected. Also, oxide particles Dy2O3 were revealed in both alloys containing dysprosium. The alloys under study were subjected to heat treatment, which included a three-stage anneal. As a result, near lamellar structure was obtained in all alloys. It has been established that the alloys containing dysprosium in the heat treated conditions demonstrated higher values of both the strength and ductility as compared to the alloy free of dysprosium. At T = 800°C, the compression mechanical properties of the alloys were found to be similar.

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