Constitutive Modeling for Tensile Behaviors of Ultra-high-strength-steel BR1500HS at Different Temperatures and Strain Rates

In order to investigate the tensile deformation behavior of ultra-high-strength-steel BR1500HS, a series of isothermal tensile experiments were carried out in a temperature range of 1023˜1123 K and a strain rate range of 0.01˜10 s−1 on a Gleeble-3500 thermo-mechanical simulator. The results indicate that the flow stress initially increases to a peak value and then decreases gradually to a steady state. Based on the analysis of the effect of strain, temperature and strain rate on flow stress, dynamic recrystallization (DRX) type softening characteristics of the stress-strain curve with single peak were identified. The flow stress level decreases with increasing temperature and decreasing strain rate. By regression analysis for Arrhenius type equation, the hot deformation activation energy Q and material constants (n, α, β and A) were calculated. Further, the Arrhenius-type constitutive equation of flow stress was developed by considering the effect of strain on the variable coefficients (including activation energy Q, material constants n, α, and A). The validity of the developed constitutive equation incorporating the influence of strain was evaluated through comparing the experimental and predicted data. Furthermore, the predictability of the developed model was also evaluated using two standard statistical parameters, correlation coefficient (R) and average absolute relative error (AARE). And R-value and AARE-value for the model are 0.997 and 4.06% respectively, which indicates that the developed model can precisely estimate the flow behavior for BR1500HS alloy throughout the entire temperature and strain rate range.