High temperature microsample tensile testing of γ-TiAl

Dislocation activity in two-phase commercial TiAl alloys occurs most readily in the γ-TiAl phase, and measurements of the physical and mechanical properties γ-TiAl are needed to provide a solid foundation for modeling the mechanical performance of these alloys. The recent development of elevated temperature microsample tensile testing is outlined and the application of this technique to elevated temperature tensile testing of γ-TiAl described. Microsample single crystal specimens of Ti–55.5% Al have been tested in tension at temperatures ranging from 400 to 1000 °C. Measurements of the Youngʹs modulus, coefficient of thermal expansion, and flow strength have been made as a function of temperature and crystal orientation. The Youngʹs modulus and coefficient of thermal expansion measurements are compared with the limited data set that is available in the literature. The flow strength data evidences a clear violation of Schmidʹs law and highlights a significant tension/compression asymmetry, both of which appear to be related to the underlying dislocation mechanisms that govern plasticity in γ-TiAl.