Evolution of Microstructure and Carbon Distribution During Heat Treatments of a Dual-Phase Steel: Modeling and Atom-Probe Tomography Experiments

Multi-Scale Modeling of Microstructure Evolution during Multi-Pass Hot-Rolling and Cooling Process

“…The CA simulation for the γ→α phase transformation includes α-phase nucleation, α-grain growth and coarsening, and carbon diffusion, which is performed based on a quantitative CA model proposed by An et al [ 29 ]. The multi-component steel used in the experiment is reduced to a ternary Fe-0.323C-1.231Mn (mol.%) alloy for simplicity.…”

“…The migration velocity of the α/γ interface V α/γ is calculated by where P α/γ is the effective driving pressure; M α/γ is the interfacial mobility of the moving α/γ interface, which can be described as [ 55 ] where is the pre-exponential factor dependent on composition and processing history. It is adjustable and ranges from 1 × 10 −4 to 0.5 mol m J −1 s −1 [ 29 ]. In the present study, is readjusted as 0.085 mol m J −1 s −1 based on the value estimated by Fazeli et al [ 56 ] and by fitting the simulation results with the experimental micrograph; Q α/γ is the activation energy for atom motion at the interface, 140 KJ mol −1 ; The effective driving pressure, P α/γ , involving the chemical driving pressure of the γ→α transformation, Δ G che , the solute drag pressure Δ G dis , and the deformation stored energy E def .…”

“…For the γ→α phase transformation in Fe-C-Mn alloys, the growth kinetics have been usually described by carbon diffusion and interface reaction based on the paraequilibrium condition, where only the interstitials are allowed to partition and reach the equality of chemical potentials between the α- and γ-phases, while the substitutional elements are not [ 34 ]. Several numerical simulation studies focused on the α-γ phase transformation during isothermal annealing [ 23 , 24 ], continuous cooling [ 25 , 26 ], continuous heating [ 27 , 28 ], and an entire anneal cycle [ 29 , 30 , 31 ] under the assumption of paraequilibrium. To account for the interaction of substitutional elements at the moving α/γ interface, Purdy et al [ 35 ] proposed a solute drag model, where the Gibbs energy dissipation due to the trans-interface diffusion of the substitutional solute was introduced.…”

“…To account for the interaction of substitutional elements at the moving α/γ interface, Purdy et al [ 35 ] proposed a solute drag model, where the Gibbs energy dissipation due to the trans-interface diffusion of the substitutional solute was introduced. An et al [ 29 ] first coupled a solute drag model with a CA model to simulate the α-γ transformation in a dual-phase steel during different heat treatment processes. The simulation results agree well with those from phase field predictions, atom-probe tomography analyses, and SEM micrographs.…”

Temperature Increases and Thermoplastic Microstructural Evolution in Adiabatic Shear-Bands in a High-Strength and High-Toughness 10 wt.% Ni Steel

“…It is emphasized that the small grain size in the ASB can also prevent the austenite from forming martensite during rapid cooling after deformation [44]. Additionally, the interstitial elements distributed in the austenite phase can also return to a local region during cooling, which was found in many air-cooled dual phase steels [66,67].…”