Precipitation behavior of hexagonal carbides in a C containing intermetallic γ-TiAl based alloy

Intermetallic gamma-TiAl based alloys are currently used as structural materials in high-temperature applications such as turbocharger wheels, valves and turbine blades. Adding C yields solid solution and precipitation hardening of the TiAl alloys, which raises their service temperature. Within this work, the effect of C on the TNM alloying system is analyzed by complementary differential scanning calorimetry measurements and selected heat treat-ments in conjunction with detailed electron microscopy analysis. This allowed the determination of the transition temperatures and revealed the precipitation onset of hexagonal Ti2AlC carbides between 1450 degrees C and 1475 degrees C. The precipitation kinetics of the carbides were further investigated by laser scanning confocal microscopy and revealed a preferred and steady growth in the length direction. Further, orientation relationships between the TiAl phases and the carbides from Blackburn and Burgers type could be determined by electron back-scatter diffraction. The results of this study provide a better understanding of the effect of C addition on the TNM alloy and thus enable further improvement of the alloying design process.

Automated summary

This study analyzed the effect of C on the TNM alloying system using differential scanning calorimetry measurements, heat treatments, and electron microscopy analysis. The results showed that adding C can raise the service temperature of the alloy and promote the precipitation of hexagonal carbides. The orientation relationships between the TiAl phases and the carbides were also determined.