Metadynamic recrystallization of austenitic stainless steel

Abstract

Interrupted torsion tests were performed in the temperature range of 900–1100°C, strain rate range of 5.0 × 10⁻²–5.0 × 10⁰/sec and interpass time range of 0.5–100 seconds to study the characteristics of metadynamic recrystallization (MDRX) for austenitic stainless steel. To compare the MDRX with static recrystallization (SRX), the pass strain was applied above the critical strain (∈_c) (∈_c = 2.2 × 10⁻³ D^1/2 ₀ Z ^0.089, where Z is Zener-Hollomon parameter, Z = ${\dot \varepsilon }$ exp((380000 J/mol)/RT) and D ₀ is as-received grain size) to obtain the MDRX during interpass time. It was found that the kinetics of MDRX were dependent of the strain rate and deformation temperature but were nearly independent of the change in pass strain after the peak strain. The time for 50% metadynamic softening, t ₅₀, was determined as follows: t ₅₀ = 1.33 × 10⁻¹¹ ${\dot \varepsilon }$ ^−0.41 D ₀ exp((230000 J/mol)/RT) and this calculated value was consistent with the measured value. The Zener-Hollomon parameter was impossible to evaluate the MDRX fraction, because the fractional softening values were different at the same Z values. The new parameter (MDRX parameter) considering deformation temperature, strain rate and interpass time was proposed to evaluate the MDRX fraction. The MDRX-parameter was determined as 3.25 × 10⁻¹⁹ ${\dot \varepsilon }$ ^0.3 t _i ^0.6 T ¹².