A Modified Constitutive Model and Dynamic Recrystallization Behavior of High‐N Mn18Cr18 Alloy

Abstract

High‐N Mn18Cr18 alloy is mainly used as drill collar (DC) and retaining rings due to its non‐magnetism and outstanding corrosion resistance. This work focuses on studying the dynamic recrystallization (DRX) behavior and thermal mechanical properties of high‐N Mn18Cr18 alloy through isothermal single‐pass compression tests on Gleeble‐3500 simulator at the temperatures from 900–1200 °C and strain rates from 0.001–1 s−1. Flow stress curves combined with metallographic analysis indicate that DRX tends to occur at high deformation temperatures and low strain rates. The deformation activation energy of high‐N Mn18Cr18 alloy is 331.775 kJ mol−1. Besides, fifth order polynomial fitting for determining critical strain and nonlinear curve fitting for extrapolating work hardening stress are presented. Based on kinetics equations of DRX and the dislocation density model, constitutive model is been set up to predict the flow stress behavior. Comparisons between the experimental and the predicted flow stress values indicate good forecast precision of the established model.

Hot Deformation Behavior and Microstructural Evolution of High Nitrogen Martensitic Stainless Steel 30Cr15Mo1N

“…The critical strain for DRX is an important parameter, and determining the required strains for initiation and completion of DRX can more accurately design an industrial hot working process. Critical strain for initiation of DRX is dependent on chemical composition of material, grain size prior to hot deformation and deformation conditions . Although critial strain can be obtained from direct microstructural observation, this technique requires considerable work and can not accurately determine the critical strain.…”

“…Many researchers mentioned that the flow cures, which show a single peak followed by a steady state flow as a plateau, indicate the occurrence of DRX during hot deformation . However, DRX actually occurs at some critical stress ( σ c ) attained at a critical strain ( ϵ c ) before peak stress . A detailed understanding of microstructural evolution as a function of deformation parameters (i.e., temperature, strain rate, and strain) is significant to realize microstructure control through the DRX process.…”

Evolution of Dynamic Recrystallization in 5CrNiMoV Steel during Hot Forming

“…Deformation temperature and strain rate had an appreciable impact on the critical strain and the peak strain. For each of the DRX characteristic true stress-strain curves, a critical strain and a peak strain were obtained [13]. Furthermore, the relationships between the peak strain and the deformation conditions and the critical strain and the deformation conditions can be, respectively, expressed as the exponential function of the Zener-Hollomon parameter.…”

“…e value of material constant C was usually between 0.3 and 0.9, which had been previously reported for steel. By substituting the values of ε p and ε c into equation (13) and regression analysis (Figure 9), the value of C was calculated to be 0.727, and the relationship between ε p and ε c was expressed as…”

“…Wu and Han [12] presented a kinetics model, and a third-order polynomial expression was fitted to determine the critical condition for the onset of dynamic recrystallization. Gan et al [13] structured the kinetics equations of DRX and a constitutive model to predict the flow stress behavior, of which fifth order polynomial fitting and nonlinear curve fitting were, respectively, presented for determining the critical strain and extrapolating work hardening stress. e research studies not only estimated the recrystallized volume fraction and grain size based on DRX models but also compared the calculated results with the experimental values [14,15].…”