Electronic edition ISSN 1574-0579

The impact of frequency modulation of alternating electromagnetic stirring on the segregation behavior during the solidification of Sn-10wt%Pb alloy: a numerical parametric study

S. Khelfi^1,2 , Ab. Abdelhakem¹ , Ab. Nouri¹ , K. Zaidat³ , L. Hachani¹

¹ Materials Physics Laboratory, Amar Telidji University of Laghouat, BP 37G, Laghouat, 03000, Algeria
² Higher Normal School of Laghouat, BP 4033, Laghouat 03000, Algeria
³ SIMAP-EPM PHELMA, University of Grenoble Alpes, BP75, 38402 Saint Martin d'Hères Cedex, France

Abstract
During alloy solidification, macrosegregation occurs due to large-scale variations in solute element concentration. The solidified metals' performance and appropriateness for a range of applications are adversely affected by this process, which results in non-uniform characteristics [1]. Researchers have discovered that one of the most used techniques to achieve high-quality castings is by applying electromagnetic stirring (EMS), which has a significant impact on the metal grain formation [2, 3, 4]. In fact, modulated alternative EMS was demonstrated to decrease the macrosegregation zone in the last solidified liquid as well as promote the columnar-equiaxed transition mechanism in comparative experiments carried out by Hachani \etal [5]. Furthermore, Wang \etal [2, 6] conducted both experimental and theoretical investigations supporting the use of alternative EMS with specific configuration. They proposed a modulation period of 4 to 20 seconds, which effectively transports rejected solute away from the solidification front. Extending previous modeling efforts, this study presents a three-dimensional, two-phase columnar solidification model that involves the time-dependent effects of electromagnetic stirring on macrosegregation and the relevant factors that have a direct effect on the columnar-equiaxed transition during the solidification of a Sn-10 wt.%Pb alloy. While earlier studies have provided valuable insights into EMS-induced flow and macrosegregation, they have precisely not addressed the coupled evolution of magnetohydrodynamic configurations and grain-scale morphology in a transient three-dimensional setting. For this purpose, a systematic parametric study is performed in an attempt to identify the optimal modulation frequency that minimizes macrosegregation, namely, the development of freckles. The model further includes key physical mechanisms, such as dendritic growth, remitting, and fragmentation, allowing for a more realistic prediction of freckle development. In addition, this work introduces a new perspective by investigating sedimentation behavior under varying EMS conditions - an aspect that has not been comprehensively addressed in prior AFRODITE-type experimental investigations. {\bf Keywords}: Solidification, Electromagnetic stirring (EMS), Macrosegregation, Segregated channels, Columnar-Equiaxed-Transition, Frequency of Modulation. Tables 1, Figs 14, Refs 64.