Physical Simulation of Hot Deformation of Low-Carbon Ti-Nb Microalloyed Steel and Microstructural Studies

Constitutive equations for the flow behavior of a 0.13 pct C-1.52 pct Mn-0.28 pct Si-0.05 pct Nb-0.052 pct Ti microalloyed steel are determined. For this purpose, uniaxial hot compression tests were performed over a wide range of strain rates (0.01 to 80 s−1) and temperatures (750 to 1050 °C). From microstructural observations, the physical processes that occurred during deformation are discussed and related to the stress-strain responses. Using sinh type constitutive equation, the average apparent activation energy for hot deformation is obtained as 359 kJ/mol. The processing map obtained using the power dissipation efficiency, η, correlates well with microstructural changes observed. In the temperature range of 825-1050 °C and strain rate range of 0.01-0.1 s−1, the strain rate sensitivity map and the power dissipation map exhibit a peak domain wherein dynamic recrystallization is the primary restoration mechanism. Safe domains of strain, strain rate, and temperature for hot working of this steel have been identified.