| The work hardening behavior of lamellar-γ two-phase TiAl alloys has been investigated through compression test at ambient temperature. The yield stress and compressive ductility showed a maximum at ∼0.5 and ∼0.32 of lamellar volume fraction, respectively. The true stress-true strain curves of lamellar-γ two-phase TiAl alloys have been analyzed using four different constitutive equations proposed by Hollomon, Voce, Ludwik, and Swift. The deformation behavior of two-phase TiAl alloys was described by Ludwik and Swift equations, which are obviously delineated by three deformation stages of work hardening. In the early stage of deformation(ε=0.01), the work hardening rate as a function of lamellar volume fraction increases linearly up to f_L=∼0.5 and establishes a nearly constant value at high lamellar volume fraction. Upon increase of the true plastic strain(ε=0.03-0.08), the work hardening rate showed a maximum at f_L=∼0.7. True plastic strain range of deformation stage II and III establishes a nearly constant value up to f_L=∼0.32 and contracts largely with the increase in the lamellar volume fraction. The compressive ductility showed the linear dependence with the work hardening exponents n_L and n_L in Crussard-Jaoul plots. The work hardening exponent n_H of Hollomon equation has a higher value of 0.3-0.5 in the deformation stage II and III. This result suggests that the deformation of lamellar-γ two-phase TiAl alloys operates through deformation twinning in addition to slip. |
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