Cleavage fracture of austenite induced by nitrogen supersaturation

Influence of Thermal and Mechanical Processing on Room Temperature Mechanical Properties of Nickel Free High Nitrogen Austenitic Stainless Steels.

“…11) This has been attributed to the increase in elastic modulus caused by increasing nitrogen content, which eventually increases cleavage stress more than plastic flow stress. Charpy V-notch impact testing was carried out in three steels M2, M3 and 2/1, which were processed as bars.…”

“…13) Similar to nitrogen, carbon is an austenite stabilising interstitial that enhances strength due to its influence on lattice expansion and Hall-Petch constant, k y . 7,9,11,12) However, the presence of carbides in the steel is reported to affect strength, ductility and toughness. 16) Literature shows that predominantly low carbon varieties of these steels are evaluated in solution treated and subsequently cold rolled condition.…”

“…11,14) The room temperature toughness levels are unusually high in these steels, 3,4) but at cryogenic temperatures they exhibit DBTT. 13) Similar to nitrogen, carbon is an austenite stabilising interstitial that enhances strength due to its influence on lattice expansion and Hall-Petch constant, k y .…”

“…-enhancement of low energy boundaries that developed sharp texture 9) -formation of very fine deformation twins at high degrees of deformation 11,14) -formation of 'Suzuki atmosphere' associated with cold deformation and low temperature annealing. 11,14) The room temperature toughness levels are unusually high in these steels, 3,4) but at cryogenic temperatures they exhibit DBTT.…”

“…[1][2][3][4][5][6][7][8][9][10][11] Increasing the nitrogen contents and cold deformation increases strength from high strengths to ultra high strength levels which are attributed to the following, -nitrogen expansion of fcc lattice [2][3][4][5] -dislocation pile-up associated with lowering of stacking fault energy 2,5,11,14) -increase in twin density and enhancement of Hall-Petch constant k y 2)…”