We have carried out a systematic investigation of the mechanisms for solid-solution hardening by nitrogen atoms and dispersion hardening by nitride particles in single crystals of austenitic stainless steels with different stacking fault (SF) energies y & = 0.02-0.2 J|m2. We show that alloying with nitrogen CN = 0-0.7 mass % and precipitation of dispersed particles leads to the appearance of an orientation dependence of the critical shearing stresses τcr, asymmetry phenomena, an orientation dependence of the slip and twinning deformation mechanisms, superelasticity, and transition from ductile fracture to brittle fracture. We develop dislocation models for solid-solution hardening by interstitial atoms, the orientation dependence and the asymmetry of τcr, based on taking into account the effect of the external stress field on the splitting of a|2<110> dislocations into partial Schockley a|6<211> dislocations and the change in the position of the interstitial atoms from octahedral interstitial sites to tetrahedral sites with a shift of the twinning a|6<211> dislocations by a Burgers vector. We establish the role of strain localization, splitting of gliding dislocations, twinning, and a high stress level in creation of strain hardening, plastic flow instabilities, and the conditions for the "brittle-ductile" transition.
ASJC Scopus subject areas
- Physics and Astronomy(all)