THERMODYNAMIC ANALYSIS OF THE SHORT-RANGE ORDER STRENGTHENING IN FE-NI-CR-N AUSTENITE

The effect of nitrogen - induced short range order and its change duri ng plastic deformation on the plastic flow behavior of Fe-Ni-Cr-N aust enite has been studied using a statistical thermodynamics model. The r esults show that the short range order makes a significant contributio n to the strength of austenite, and that the reduction in its degree d ue to the passage of dislocations on the same slip plane can account f or the occurrence of planar slip in the austenite with nitrogen. An an alysis of the thermally activated behavior of the dislocation motion w as conducted in order to quantify the temperature dependence of yield stress. It is found that, while the short range order gives rise to a somewhat larger temperature dependence of yield stress relative to tha t found in the conventional f.c.c. metallic materials, it still can no t fully account for the measured values in the Fe-Ni-Cr-N austenite.