WORK-HARDENING, STRENGTH AND DUCTILITY IN THE HOT-WORKING OF 304 AUSTENITIC STAINLESS-STEEL

Stress-strain curves, generated through continuous hot torsion tests of as-cast and worked type 304 austenitic stainless steel in the range 1200-900°C and 0.1-5.0 s-1, were analysed with respect to the characteristics of work hardening, dynamic recovery, dynamic recrystallization and ductility. The work-hardening behaviour was related to the Kocks-Mecking model where the saturation stress is due to dynamic recovery. Furthermore, the associated activation enthalpy ranged from 274 to 392 kJ mole-1 as the temperature increased. Through sinh analysis, the activation energy was determined to be 393 kJ mole-1 and was also corrected upwards in consideration of deformational heating. The time-to-fracture criterion was shown to qualitatively represent the hot heating. The time-to-fracture criterion was shown to qualitatively represent the hot ductility, which rose with increase in both temperature and strain rate.