Microstructures and mechanical properties of directionally solidified C-containing γ-TiAl alloys via electromagnetic cold crucible

Abstract

TiAl alloys with nominal compositions of Ti–47Al–2Nb–2Cr-(0.2, 0.5)C were prepared via electromagnetic cold crucible directional solidification. Effects of alloying element carbon on the solidification behavior, microstructure and mechanical properties of the TiAl alloy were investigated. Experimental results revealed that alloying with carbon reduced the B2 phase content and refined the lamellar structure. Also, additions of 0.5 at.% carbon changed the primary phase from single β to the mixture of β and α, and promoted the formation of Ti2AlC particles. The yield strength of the alloy enhanced as the carbon content increased, while the ultimate strength of the alloy containing 0.2 at.% and 0.5 at.% C decreased consequently. Dislocation glide governed the plastic deformation of the two directionally solidified C-containing TiAl alloys. The strain rate sensitivity value and activation volume of the both experimental alloys decreased with the increase of strain. The hindrance of Ti2AlC particles to dislocations movements caused stress concentration and premature cracking.