Dynamic strain aging of austenitic high nitrogen Cr-Ni and Cr-Mn steels

Dynamic strain aging (DSA) of solution annealed Cr-Ni and Cr-Mn type austenitic high nitrogen steels (HNS) was investigated by means of tensile tests. Nitrogen content of the steels varied from 0.26 to 1.00 wt. %. Tensile tests were performed at strain rates from 0.00005 to 0.03 1/s between room temperature and 800 °C. Austenitic HNSs exhibit DSA at elevated temperatures, which is caused by interactions between diffusing solute atoms and moving dislocations. Low activation energies for plastic deformation in the studied steels indicate that the diffusion mechanism is pipe diffusion below 600 °C, and also bulk diffusion at 800 °C. An activation energy for nitrogen diffusion of about 1.95 eV was determined by internal friction measurements.