Aj. Craven et al., Complex heterogeneous precipitation in titanium-niobium microalloyed Al-killed HSLA steels - I. (Ti,Nb)(C,N) particles, ACT MATER, 48(15), 2000, pp. 3857-3868
Precipitation in Ti-Nb Al-killed microalloyed HSLA steels (Ti/N weight rati
o from 4.4 to 1) was investigated in both the as-rolled and the normalised
conditions using analytical electron microscopy including parallel electron
energy loss spectroscopy (PEELS). An extensive formation of heterogeneousl
y nucleated complex (Ti,Nb)(C,N) particles down to 10 nm in size was observ
ed. The core of such a complex particle is based on TIN and has a spherical
, cubic or cruciform shape. The N/(TI + Nb) atomic ratio in the core is sim
ilar to the average value in the steel whereas the Nb/Ti ratio is much smal
ler than the average value and not proportional to it. Many of the cores ha
ve caps in the form of epitaxial overgrowths based on NbC. Their compositio
n changes from Nb(C,N) to (Nb,Ti)C as the N/Ti ratio decreases. The formati
on of these complex particles and their detailed morphology are controlled
by the processing conditions as well as the overall composition. (C) 2000 A
cta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserve
d.