The controlling factors in primary creep of TiAl-base alloys

Analysis of the primary creep data of various TiAl alloys indicated that the primary creep strain of TiAl alloys significantly depends on the stress. At low stress level, the primary strain of TiAl is low irrespective of microstructure and composition. At high stresses, the primary strain of TiAl varies largely with the microstructure and alloying additions. Low primary creep strain can be obtained through W addition, precipitation hardening and lamellar refinement. Stress-induced phase transformation, twinning and dislocation multiplication are considered to be the dominant processes controlling the primary creep of TiAl. Stabilization treatment such as aging is critically important for many TiAl alloys to decrease the primary strain. The analysis suggests that large primary creep strain is only a concern for TiAl at high stresses but not for many target applications in the stress range of 40–150 MPa.