1996 Volume 37 Issue 4 Pages 643-649
The non-stoichiometry of carbides and carbo-nitrides in Ti and Ti & Nb bearing ultra low carbon steels is studied using Energy Dispersive X-ray Spectroscopy (EDXS) and plasmon energy (Ep) measured with Electron Energy Loss Spectroscopy (EELS) in a Field-Emission Transmission Electron Microscope (FE-TEM). We have examined Ep of carbides and carbo-nitrides in order to determine their compositions. The X values in precipitates identified as TiCx and (Ti,Nb)Cx were 0.82∼0.87, 0.87∼0.89 and 0.90∼0.91 in 0.04mass%, 0.08mass%Ti and 0.10mass%Ti & 0.01mass%Nb-bearing steels, respectively. It can be seen that the X values in TiCx and (Ti,Nb)Cx approach 1 as the metallic concentration in the steels is increased. The atomic ratio of Ti/Nb in (Ti,Nb)Cx precipitates was 90/10. The size of the carbides was between 20 and 70 nm, but Ep has no dependence on the size of the precipitates.
We have also quantified the (Ti,Nb)(C,N)x precipitates in the 0.10mass%Ti & 0.01mass%Nb-bearing steel. The atomic ratio of Ti/Nb and C/N is 90/10 ∼ 95/5 and 0.35/0.65, and the X value of (Ti,Nb)(C,N)x is estimated as about 0.85∼0.90.
