The Strain Dependence of Post-Deformation Softening during the Hot Compression of 304H Stainless Steel |
| Journal |
Materials Science Forum (Volumes 539 - 543) |
| Volume |
THERMEC 2006 |
| Edited by |
T. Chandra, K. Tsuzaki, M. Militzer , C. Ravindran |
| Pages |
100-107 |
| DOI |
10.4028/www.scientific.net/MSF.539-543.100 |
| Online since |
March, 2007 |
| Authors |
John J. Jonas,
Evgueni I. Poliak,
A. Najafizadeh
|
| Keywords |
304H Stainless Steel, Metadynamic Recrystallization, Softening Kinetics |
| Abstract |
Experiments were carried out in which the dependence of the fractional softening on
temperature, time and strain rate was determined in a 304H stainless steel. Three prestrain ranges were
identified pertaining to three different post-deformation softening behaviors: 1) prestraining to below the
DRX critical strain: strongly strain dependent softening by SRX alone with softening kinetics controlled
by growth rate of the nuclei; 2) prestraining to above the DRX critical strain: SRX + MDRX softening
with weaker strain dependence of the kinetics but still controlled by grain growth; 3) at a prestrain of ε*
and beyond: nucleation-controlled MDRX softening with the full inhibition of SRX. The transition
prestrain ε* can exceed the peak strain if the DRX grain refinement ratio g = D0/DDRX > 4. The
transition to MDRX-dominated softening can be attributed to a constant value of the normalized strain
hardening rate independent of the preloading temperature and strain rate. The softening data from the
compression tests show that at ε*, the time for half softening t50 exhibits a minimum. These data differ
somewhat from observations obtained in the torsion testing of solid bars, in which no strain dependence
of t50 was detected at ε* and beyond. Whether or not the strain dependence of t50 vanishes in the MDRX
range is sensitive to the test method employed to study the post-deformation softening. |
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