Metadynamic recrystallization of austenitic stainless steel

Interrupted torsion tests were performed in the temperature range of 900-11 00 degreesC, strain rate range of 5.0 x 10(-2)-5.0 x 10(0)/sec and interpas s time range of 0.5-100 seconds to study the characteristics of metadynamic recrystallization (MDRX) for austenitic stainless steel. To compare the MD RX with static recrystallization (SRX), the pass strain was applied above t he critical strain (epsilon (c)) (epsilon (c) = 2.2 x 10(-3) D-o(1/2) Z(0.0 89), where Z is Zener-Hollomon parameter, Z = (epsilon) over dot exp((38000 0 J/mol)/RT) and D-0 is as-received grain size) to obtain the MDRX during i nterpass 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(5)0 = 1.33 x 10(-11) (epsilo n) over dot (-0.41) D-0 exp((230000 J/mol)/RT) and this calculated value wa s consistent with the measured value. The Zener-Hollomon parameter was impo ssible to evaluate the MDRX fraction, because the fractional softening valu es were different at the same Z values. The new parameter (MDRX parameter) considering deformation temperature, strain rate and interpass time was pro posed to evaluate the MDRX fraction. The MDRX-parameter was determined as 3 .25 x 10(-19) (epsilon) over dot(0.3) t(i)(0.6) T-12. (C) 2001 Kluwer Acade mic Publishers.