Composition of vanadium carbonitride precipitates in microalloyed austenite

Journal Article · Thu Nov 01 04:00:00 EST 1984 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(84)90114-5· OSTI ID:6463152

Speer, J G; Hansen, S S; Mehta, S

It is the purpose of this paper to present a model which describes equilibrium precipitation in austenite in the Fe-V-C-N system, and to discuss the implications of this model with regard to previous studies of precipitation behavior in this system. The equilibrium precipitates are taken to be compositionally homogeneous, and no attempt is made to calculate the initial precipitate composition or to describe the approach to equilibrium. The model which we propose assumes that the excess free energy of mixing of VC and VN can be described using the regular solution model developed by Roberts et al. At a given temperature, T, the steel, matrix, and precipitate compositions must lie on a common tie line (which will occur if certain mass-balance relationships are satisfied). Assuming that the vanadium carbonitrides are perfectly stoichiometric (i.e., VC /SUB x/ N /SUB 1-x/ )*, there are five unknowns for which to solve: the equilibrium precipitate composition (x), the precipitate mole fraction (f), and the equilibrium levels of vanadium, carbon, and nitrogen ((V /SUB m/ ), (C /SUB m/ ), and (N /SUB m/ )) in the austenite matrix. The equilibrium condition is determined by solving simultaneously the following nonlinear equations: In summary, a thermodynamic model has been developed which describes equilibrium carbonitride precipitatin behavior in vanadium steels. Results obtained using the new model deviate substantially, in some cases, from those which have been predicted previously.

• Research Organization: Research Department, Bethlehem Steel Corporation, Bethlehem, PA
• OSTI ID: 6463152
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 18:11; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
ALLOYS
AUSTENITE
CARBIDES
CARBON ADDITIONS
CARBON COMPOUNDS
CARBON NITRIDES
CHEMICAL COMPOSITION
ENERGY
FABRICATION
FINITE DIFFERENCE METHOD
FREE ENERGY
HEAT TREATMENTS
IRON ALLOYS
ITERATIVE METHODS
MATERIALS WORKING
MATHEMATICAL MODELS
NITRIDES
NITROGEN COMPOUNDS
NONLINEAR PROBLEMS
NUMERICAL SOLUTION
PHYSICAL PROPERTIES
PNICTIDES
PRECIPITATION
SEPARATION PROCESSES
THERMODYNAMIC PROPERTIES
THERMOMECHANICAL TREATMENTS
TRANSITION ELEMENT COMPOUNDS
VANADIUM CARBIDES
VANADIUM COMPOUNDS
VANADIUM NITRIDES