Aj. Craven et al., Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels - II. Non-titanium based particles, ACT MATER, 48(15), 2000, pp. 3869-3878
An analytical electron microscopical investigation of three Ti-Nb Al deoxid
ized steels with different N:Ti ratios has been undertaken. In each steel,
a large number of small ( < 10 nm) particles were observed. Parallel electr
on energy loss spectroscopy (PEELS) showed that their compositions in the t
hree steels were consistent with those reported for the caps on the TiN cor
es in the equivalent steels in Part I, i.e. NbC0.7N0.3, NbC and (Nb0.7Ti0.3
)C, respectively. The Nb incorporated in these caps added to that dissolved
in the TiN cores results in a significant reduction in the number of small
particles which give effective dispersion hardening. The size of this redu
ction depends on a number of competing factors. AlN precipitation also occu
rred in the as-rolled steel with highest N content and in the normalized st
eels with the two higher N contents. AlN is usually expected to control the
austenite grain growth. NbC-based material grew on the AlN. A dendritic co
mplex based on the iso-structural compounds MnSiN2 and AlN was observed in
the high N steel. (C) 2000 Acta Metallurgica Inc. Published by Elsevier Sci
ence Lid. All rights reserved.