M. Burtscher, K. Kirchheimer, I. Weißensteiner, C. Bernhard, B. Lederhaas, T. Klein, S. Mayer, H. Clemens
September 25, 2018
In an intermetallic γ-TiAl alloy possessing the nominal composition of Ti-43Al-4Nb-1.5Mo-0.5C-0.1B (in at. %), the precipitation behavior of the hexagonal Ti 2 AlC phase was studied using complementary metallographic methods. By the addition of C, the alloy can be solid solution strengthened and precipitation hardened. However, during an annealing process, coarse H carbides are formed in the β single-phase field which is practically insoluble for carbon. These coarse carbides are under the scope of this investigation. After determining the area of existence of the phase fields by means of differential scanning calorimetry, the occurrence and the morphology of the H-carbides were analyzed by applying specific heat treatments in the area of the α + β → β phase transformation. By the use of a laser scanning confocal microscope, the formation of the carbides was tracked in-situ as well as their growth kinetics determined. The mutual orientations of the microstructural constituents were determined in an scanning electron microscope by means of electron backscatter diffraction. Therefore, the specimen was not subjected to an additional surface treatment. Thus, the orientation relationship between the α 2 -Ti 3 Al phase and the H carbides could be verified and their formation within a C containing intermetallic TiAl-alloy could be illuminated.