Precipitation in V bearing microalloyed steel containing low concentrations of Ti and Nb
Authors: Shanmugam, S.; Tanniru, M.; Misra, R. D. K.; Panda, D.; Jansto, S.
Source: Materials Science and Technology, Volume 21, Number 8, August 2005 , pp. 883-892(10)
Publisher: Maney Publishing
Abstract:The paper describes the precipitation behaviour in a thermomechanically processed V bearing microalloyed steel containing small additions of Ti and Nb (0·007–0·008 wt-%) using analytical transmission electron microscopy. An intriguing aspect is the significant precipitation of titanium and niobium at these low concentrations, contributing to strength. A high density of multimicroalloyed precipitates of (V, Nb, Ti)(C, N) are observed instead of simple TiN, TiC, and NbC precipitates. They are characterised as cuboidal (45–70 nm), spherical (20–45 nm), irregular (20–45 nm), and fine (10–20 nm). Estimation of solubility products of carbides and nitrides of V, Nb, and Ti implies that the precipitation of titanium occurs primarily in austenite. Interphase precipitation of niobium occurs during austenite to ferrite transformation, while complete precipitation of vanadium takes place in the austenite–ferrite region close to completion of transformation. Substoichiometric concentrations of Ti and Nb, the presence of nitrogen, and the mutual extensive solubility of microalloying carbonitrides explains the formation of core shell (triplex/duplex) precipitates with highly stable nitrides ((Ti, Nb, V)N) in the core and carbides ((Ti, Nb, V)C) in the shell. The qualitative stochiometric ratios of triplex and duplex carbonitrides were Ti0·53Nb0·35V0·12 and Ti0·6V0·4, Nb0·51V0·49 and Ti0·64Nb0·36. Extensive precipitation of fine carbides on dislocation substructures, and sub-boundaries occurred. They were generally characterised as vanadium carbide precipitates with ordered cubic L12 structure and exhibited a Baker–Nutting orientation relationship with the ferrite matrix. M4C3 types of carbides were also observed similar to the steel, having high concentrations of Ti and Nb.
Document Type: Research Article
Publication date: 2005-08-01
Authors wishing to cite fast track papers should give the journal name and the article DOI. This will enable reference linking via CrossRef and allow forward and backward citation tracking systems to associate the fast track citation with the final journal reference.Materials Science and Technology is the successor of two previous titles, for which digitised archives are available: Metal Science (Vols. 1—17; 1967—84) and Metals Technology (Vols. 1—11; 1974—84).
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