Vg. Gavriljuk et al., EFFECT OF NITROGEN ON THE TEMPERATURE-DEPENDENCE OF THE YIELD STRENGTH OF AUSTENITIC STEELS, Acta materialia, 46(4), 1998, pp. 1157-1163
Citations number
26
Categorie Soggetti
Material Science","Metallurgy & Metallurigical Engineering
The temperature dependence of the yield strength R-p0.2 in the range o
f 4-300 K is studied on Cr18Ni16Mn10 steel alloyed with nitrogen or ca
rbon or having no interstitials introduced purposefully. A striking in
crease of the yield strength of nitrogen steel was observed at tempera
tures below 100 K in accordance with previous results. The temperature
dependence of stacking fault energy (SFE) in the range 300-130 K was
measured by means of transmission electron microscopy and it was shown
that nitrogen causes a sharp decrease of the SFE with decreasing temp
erature while no marked temperature dependence of the SFE was observed
in carbon steel. Samples of the studied steels were deformed by tensi
on at 77 K and their dislocation structure was studied at room tempera
ture. Tangled dislocations were observed in N(C)-free and C-alloyed au
steniles while the obvious splitting of dislocations occurred in the n
itrogen one. This result was attributed to the low SFE in nitrogen aus
tenite at 77 K and an effect of interstitial atoms segregated on split
dislocations during low temperature plastic deformation, keeping the
splitting after deformation and heating to room temperature. The effec
t of nitrogen on SFE is explained based on the results of the studies
of electron structure of nitrogen austenitic steels and it is attribut
ed to an increase in the density of states at the Fermi surface due to
nitrogen. The results obtained enable one to interpret the nitrogen e
ffect on the yield strength of austenitic steel within the framework o
f Seeger's theory. (C) 1998 Acta Metallurgica Inc.