Multiscale Modeling of Phase Transformations in Steels

Abstract

Multiscale modeling tools have great potential to aid the development of new steels and processing routes. Currently, industrial process models are at least in part based on empirical material parameters to describe microstructure evolution and the resulting material properties. Modeling across different length and time scales is a promising approach to develop next-generation process models with enhanced predictive capabilities for the role of alloying elements. The status and challenges of this multiscale modeling approach are discussed for microstructure evolution in advanced low-carbon steels. Firstprinciple simulations of solute segregation to a grain boundary and an austenite-ferrite interface in iron confirm trends of important alloying elements (e.g., Nb, Mo, and Mn) on grain growth, recrystallization, and phase transformation in steels. In particular, the linkage among atomistic simulations, phase-field modeling, and classic diffusion models is illustrated for the effects of solute drag on the austenite-to-ferrite transformation as observed in dedicated experimental studies for iron model alloys and commercial steels.

In Situ High-Temperature EBSD and 3D Phase Field Studies of the Austenite–Ferrite Transformation in a Medium Mn Steel

“…Many models have been proposed to incorporate the effect of various parameters on the rate of interface migration during ferrous phase transformations, as nicely summarized in a comprehensive review paper (Gouné et al, 2015). In such models, the phase transformation is modeled by reducing the actual interface to a mathematical surface characterized with multiple variables and parameters such as the interface thickness (Svoboda et al, 2011), trans-interface diffusivity (Gamsjäger & Rettenmayr, 2015), interface energy (Militzer et al, 2014) and crystallographic orientation relationship (OR) between two crystals in contact (Ecob & Ralph, 1981). Yet, all these models explicitly or implicitly assume that the local interface movement is the same for each interface and does not vary along a particular interface, except near triple lines and quadrupole points.…”

Open Questions in Nanosegregation

“…Only three theoretical values show larger difference than the above mentioned interval (i.e. ±34 kJ mol −1 ): those for segregation of silicon[14], aluminum[11] and molybdenum[20] at specific grain boundaries of α-iron. However, in all these cases no interaction is referred in literature.…”

Progress in elemental segregation and solute drag effect at the austenite/ferrite interface

“…原子尺度模拟元素偏聚与界面的交互作用可获 得许多介观尺度模型难以捕捉且反常理的物理现象, 所用的模拟手段涵盖第一性原理计算(DFT) 、分子 动力学(MD) 、动力学蒙特卡洛(kMC)等 [89] .…”