TERENTYEV Maxim St.Petersburg State Polytechnical University

Spoluautoři KODZHASPIROV George

The influence of the hot deformation parameters on the alloy UNS6690 microstructure evolution and stress-strain curve behavior is presented. Physical simulation using torsion tests has been realized at the different deformation temperatures (1150°C, 1050°C and 900°C) and strain rates (0.5, and 5 s-1). The flow stress curves showed an initial strain-hardening followed by peak stress revealing the occurrence of dynamic recrystallization. It was noted that peak stress values increase with the increasing of strain rate and decreasing of deformation temperature. The microstructural analysis showed that the first dynamically recrystallized grains appear before the peak strain, εp (approximately at 0,5-0,8εp) and that the size of the dynamically recrystallized grains does not exceed 75μm. In the deformed samples the average grain size decreases from 170 μm (initial grain size before deformation) up to 40-105 μm. This fining of microstructure can be associated both with appearance and growth of the new dynamically recrystallized grains and with the formation of subgrains with high angle misorientation inside the non-recrystallized deformed grains result in strain accumulation. Equations allowing to predict the stress-strain curve behavior under different hot deformation conditions were obtained. Derived equations after their integration into a finite element model can be used for a simulation of a real metal forming process of the alloy.