Ricardo Siquieri

Investigating heterogeneous nucleation in peritectic materials via the phase-field method

Here we propose a phase-field approach to investigate the influence of convection on peritectic growth as well as the heterogeneous nucleation kinetics of peritectic systems. For this purpose we derive a phase-field model for peritectic growth taking into account fluid flow in the melt, which is convergent to the underlying sharp interface problem in the thin interface limit (Karma and Rappel 1996 Phys. Rev. E 53 R3017). Moreover, we employ our new phase-field model to study the heterogeneous nucleation kinetics of peritectic material systems. Our approach is based on a similar approach towards homogeneous nucleation in Granasy et al (2003 Interface and Transport Dynamics (Springer Lecture Notes in Computational Science and Engineering vol 32) ed Emmerich et al (Berlin: Springer) p 190). We applied our model successfully to extend the nucleation rate predicted by classical nucleation theory for an additional morphological term relevant for peritectic growth. Further applications to understand the mechanisms and consequences of heterogeneous nucleation kinetics in more detail are discussed.

Phase-field investigation of microstructure evolution under the influence of convection

Numerical simulation of solidification and crystal growth has attracted industrial attention as a powerful engineering tool for processes and alloy optimization. In this work, we present a detailed study of the influence of flow on microstructure evolution during solidification. First, we include convection effects into an existing quantitative phase-field model that is meant to simulate dendritic growth of a binary alloy. We apply it to investigate the solidification of a Fe-Mn alloy under external flow conditions. In addition, we present an extension of the quantitative phase-field model of two-phase growth which includes natural and forced convection effects in the melt phase. We use this extension to investigate directional solidification of eutectic lamellae under the influence of convection as well as microstructure formation of peritectic growth in the presence of convection.

Prediction of Microstructure and Microsegregation in a Fe-Mn-C Austenitic Steel based on Phase-field Microstructure Simulations

This paper presents an experimental and theoretical investigation of the microstructure formation and segregation behaviour of a new austenitic steel based on the Fe-Mn-C alloy system. In order to accomplish the simulations, a modification of the model by Cha et al. is introduced. It includes a correction which compensates for artificial solute-trapping. A good qualitative agreement is found between the simulated 2D microstructures and the corresponding micrographs. Both simulations and experiments show that this alloy is very prone to manganese segregation. The further investigation on this field is scheduled.

Phase-Field Simulation of Solidifying Microstructure in the Presence of a Convective Field

Here we present a contribution to the microstructure based design of new steel alloys by a careful investigation of multiphase microstructure solidification in a convective field. To this end we present an extension of the quantitative phase-field model proposed in [1] to investigate the influence of hydrodynamic convection on the growth of eutectic/peritectic alloys. We study directional solidification of a eutectic alloy under the influence of a shear flow ahead of the solidifying front. We mainly investigate the growth of a eutectic lamellar structure. We show that the imposed flow tilts the whole lamellar structure away from the flow direction. Moreover, we show that forced flow alters the growth morphology of Fe-Ni peritectic alloys, having a strong influence on the nucleation of the peritectic phase. Based on these investigations, a scale relation between the strength of flow and the solid volume fraction is derived. Further we propose an application of these models as an alternative approach to study heterogeneous nucleation kinetics in the solidification of peritectic materials systems.