| The constant load creep test has been conducted in order to estimate the temperature and stress dependence of the steady-state creep behaviour of the TiAl base cast alloys, Ti-47Al-2Mn and Ti-48Al(at.%), respectively. Two microstrutural conditions were evaluated as follows : FL scheme consisting of a coarse grained fully transformed lamellar structure with α₂/γ lath within a grain, and duplex scheme consisting of fine grained equiaxed γ with α₂/γ lamellar. Steady-state creep behaviour of the both microstructural conditions was studied as a functions of stresses between 70 and 300MPa, and temperatures between 700 and 900℃. Apparent creep activation energies and stress exponents were measured for both microstructural conditions in each composition. The temperature and stress dependence of the steady-state creep rate of bath microstructures can be described well by the power law creep equation. Therefore, dislocation motion is proposed as a predominant creep mechanism in the stresses and temperature regime investigated in this study. At temperatures and stress levels in which the present investigation was made, the steady-state creep rate of the FL structures exhibits an order of magnitude lower than that of the duplex ones. |
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