Abstract
Hot compression tests of as-cast Ti-45Al-9Nb alloy (in at.%) were conducted in the temperature range of 1473 to 1548 K and at the strain rates of 0.01 to 0.1 s^–1. The deformation activation energy Q was determined as 524.89 kJ mol^–1 by the Hyperbolic-sine constitutive equation. To select a preferable model to describe the relationship between stress and strain, both the dynamic softening model and the modified Arrhenius constitutive model have been developed to predict the stress-strain curves of the high Nb containing TiAl based alloy during hot deformation. Due to the constant material parameter of c, the flow stress predicted by the dynamic softening model had a large error with the measured stress.
Moreover, the deviation between the predicted and experimental data increased with the increase in strain rate and the decrease in temperature. When the material constant is expressed as the polynomial function of true strain, the Arrhenius constitutive model is modified to predict the flow stress, which is in good agreement with the experiment. This indicates that the modified Arrhenius constitutive model can accurately predict and analyze the hot deformation behavior of the as-cast Ti-45Al-9Nb alloy.

Key words
high Nb containing TiAl alloy, hot compression test, dynamic softening model, modified Arrhenius constitutive model, stress prediction

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