Abstract:The high-temperature flow behavior of TC11/Ti-22Al-25Nb electron beam (EB) weldments was investigated by the isothermal compression tests at the temperature of 900-1060 °C and the strain rate of 0.001-10 s^-1. Based on the experimental data, the constitutive equation that describes the flow stress as a function of strain rate and deformation temperature is obtained. The apparent activation energy of deformation is calculated, which decreases with increasing the strain and the value is 334 kJ/mol at strain of 0.90. The efficiency of power dissipation η changes obviously with the variation of deformation conditions. Under the strain rates of 0.01, 0.1 and 1 s^-1, the value of η increases with increasing the true strain for different deformation temperatures. While the value of η decreases with increasing the strain under the strain rates of 0.001 and 10 s^-1. The optimum processing condition is (t_opi=1060 °C, _opi=0.1 s^-1) with the peak efficiency of 0.51. Under this deformation, dynamic recrystallization (DRX) is observed obviously in the microstructure of welding zone. Under the condition of 1060 °C and 0.001 s^-1, the deformation mechanism is dominated by dynamic recovery (DRV) and the value of η decreases sharply (η=0.02). The flow instability is predicted to occur since the instability parameter ξ( ) becomes negative. The hot working process can be carried out safely in the domain with the strain rate of 0.001-0.6 s^-1 and the temperature of 900-1060 °C.

Key words: dual-alloy; hot deformation; processing map; apparent activation energy; microstructure