Abstract:
The effect of nitrogen content on the dynamic strain ageing (DSA) behaviour of type 316LN
austenitic stainless steel has been studied. The nitrogen content was varied from 0?07 to 0?22 wt%.
The tensile tests were carried out over a temperature range of 300–1123 K and at three strain
rates in the range 3610 23 –3610 25 s 21 . Serration was observed in the load elongation curves in
the intermediate test temperature range and has been considered due to DSA phenomenon. The
critical strain to onset of serrated flow increased with increase in nitrogen content and strain rate.
The temperature for onset of DSA and the temperature of disappearance of DSA were found to
increase with the increase in nitrogen content. The variations in tensile strength and work
hardening rate of the steel with temperature exhibit peak values in the intermediate temperature
range and have been attributed due to DSA phenomenon. The activation energy for DSA,
estimated based on the temperature and strain rate dependences of the strain to onset of
serrated flow, was found to increase from 111 to 218 kJ mol 21 with the increase in nitrogen
content from 0?07 to 0?22 wt-% and the increase has been attributed to the possible enhanced
interaction of the DSA causing interstitial nitrogen with substitutional chromium.
