Grain boundary strengthening in austenitic nitrogen steels

The effect of nitrogen and carbon on the strengthening of the austenitic st eel Cr18Ni16Mn10 by grain boundaries is studied. It is established in accor dance with previous results that, in contrast to carbon, nitrogen markedly increases the coefficient k in the Hall-Fetch equation. Because of a pronou nced planar slip induced by nitrogen and the absence of ally noticeable seg regation of nitrogen atoms at the grain boundaries, nitrogen austenite pres ents an excellent object for testing different existing models of grain bou ndary strengthening (pile-up of dislocations, grain boundary dislocation so urces, work hardening). Based on the analysis of available data and measure ments of interaction between nitrogen or carbon atoms and dislocations it i s shown that the nitrogen effect can be attributed to a strong blocking of dislocation sources in grains adjacent to those where the slip started. (C) 1999 Elsevier Science S.A. All rights reserved.