The effect of melt flow induced by RMF on the meso- and micro-structure of unidirectionally solidified Al–7wt.% Si alloy Benchmark experiment under magnetic stirring

Abstract

This work deals with the effect of melt flow on the solidified structure by RMF. The microstructure of the first non-stirred part of the Al-7Si alloy is columnar. After switching on stirring first a transient zone was formed with eutectic “cupola”. After the first transient zone, the “Christmas Tree Like” microstructure was formed. During the solidification of stirred part, a “tulip-like” interface evolves. During the last two decades, many algorithms were developed to simulate the solidification process for different casting methods like ingots, continuous casting of steel and the direct chill cast of aluminum. Experiments performed under exactly known conditions and with the detailed knowledge of meso- and micro-structures are required for validating these simulations. The aim of this paper is to give a data set to validate these simulations. Unidirectional solidification experiments were performed by using a rotating magnetic field (RMF) to study the effect of melt flow on the solidified micro- and meso-structure of the Al–7wt.% Si binary alloy. The first and the third 1/3 parts of samples were solidified without magnetic stirring, and the second (middle) 1/3 part was solidified by using magnetic stirring. The magnetic induction was 10 mT, the temperature gradient was ∼7 K/mm, and the sample movement velocity was 0.1 mm/s. On the longitudinal section of the sample, the columnar/equiaxed transition (CET), the equiaxed/columnar transition (ECT), the secondary dendrite arm spacing (SDAS), and the macrosegregation (concentration distribution and the amount of eutectic) were investigated. The primary dendrite arm spacing (PDAS) and the grain structure were studied on the cross-section after color etching. The effect of melt flow induced by RMF on the meso- and microstructure of unidirectionally solidified Al–7wt.% Si alloy Benchmark experiment under magnetic stirring .