Macrosegregation Evolution in Eutectic Al-Si Alloy under the Influence of a Rotational Magnetic Field

Round 1

Reviewer 1 Report

Praca jest bardzo ciekawa, dotyczy kontroli struktury stopów podczas jednokierunkowej krystalizacji w polu magnetycznym. Generalnie nie mam uwag do całej pracy. Praca jest zrozumiała. Istnieją jednak pewne wątpliwości co do gradientu temperatury G. A gradient temperatury jest jednym z parametrów procesu krystalizacji jednokierunkowej. Dlatego mam pytania:

- Jak zmierzono gradient temperatury G?

- Do jakiego miejsca w próbce odnosi się gradient temperatury G?

- Myślę, że powinien to być gradient temperatury G w cieczy na froncie krystalizacji. Wówczas podanie wartości gradientu temperatury G na froncie krystalizacji ma sens, ponieważ front krystalizacji odpowiada za strukturę stopu.  

- A czy gradient temperatury na froncie krystalizacji może być zmienny dla odpowiedniej indukcji magnetycznej?

The work is very interesting, it concerns the control of the structure of alloys during unidirectional crystallization in a magnetic field. In general, I have no comments on the whole work. The work is understandable. However, there are some doubts as to the temperature gradient G. And the temperature gradient is one of the parameters of the unidirectional crystallization process. That's why I have questions: - How was the temperature gradient G measured? - To what point in the sample does the temperature gradient G relate? - I think it should be the temperature gradient G in the liquid at the crystallization front. Then specifying the value of the temperature gradient G at the crystallization front makes sense, because the crystallization front is responsible for the alloy structure. - And can the temperature gradient on the crystallization front be changeable for the appropriate magnetic induction?

Author Response

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Reviewer 2 Report

The effect of fluid flow on the microstructural evolution is an important aspect in solidification sciences. In the present work flow effects are investigated on eutectic Al-Si alloys directionally solidified using a Bridgman furnace and applying rotating magnetic fields with different levels of field strengths while solidification velocity and temperature gradient were kept constant. The analysis of the microstructure of as-solidified samples by optical and scanning electron microscopy reveals a distinct effect of fluid flow on growth mechanism and the evolution of the microstructure. It is found that coupled eutectic growth of Al and Si phase is replaced by primary dendritic growth of Al with interdendritic eutectic solidification as the field amplitude is increased. Secondly, stirring has a clear influence on macrosegregation in terms of enrichment of the liquid with Si leading to primary growth of the Si phase at a later stage of solidification.

The experiments are well conducted, the results and the conclusions are convincing. The manuscript is clear and understandable. There are only minor comments:

 

1. I guess that the simulated flow pattern in Figure 1.b is taken from literature, correct? The reference should be given in the figure caption. What is the unit of flow velocities in Figure 1.b? Is it mm/s? What was the field strength applied in the simulation? The question is whether the flow velocities in the present experiments are comparable to calculated velocities shown in Figure 1. The order of magnitude of flow velocities that are expected when stirring with field amplitudes between 20 and 150 mT should be addressed in section 2.3

2. The 3 bullet points on page 6, line 197-200 obviously concern the solidification process of sample D which is already described in Table caption 1. They can be deleted.

2. In Figure 7 the sum of the fractions of eutectic structure and primary should amount to 100% (at B = 60 mT it is 80 plus 21).

3. Why is the Al phase selected as the primary growing phase upon stirring and not Si? Is there an explanation for the physical origin? As it is a major result a more detailed description and discussion in chapter 5, pages 13, 14 would be desired.

Author Response

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Reviewer 3 Report

   The authors have studied the effect of rotating magnetic field (RMF) on solidification process of Al-Si of eutectic compositions. Observed results are interested in the field of solidification; therefore, the report is valuable for publication. However, the present manuscript is not recommended as this style to accept for publication. The author should revise the present manuscript for according to the following comments.

  The present manuscript does not clearly and enough explain for the purpose of this research; thus, we are not able to read out what are the new findings and information in the present research.  Present manuscript is described only current understanding status for the research of Al-Si solidification and it under the RMF. In Introduction section, you should describe your research purpose in the Al-Si solidifications what do you want to clarify or understand in the phenomena in Al-Si solidifications. Also, authors do not describe details of the RMF generation and its conditions during solidification experiments. In present manuscript only magnetic field intensity was described. You should describe more details for RMF generations and conditions. After revising the present manuscript, we should need a re-review process.

Author Response

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Reviewer 4 Report

The aim of this study should be clearly described in the Introduction.

Scale bars should be given in the microstructure photographs.

Errors in the figure number and the reference number should be corrected.

The caption of Fig. 11 should be rewritten.

Si concentration profiles in Step 3 area should be given

Solidification mechanism of primary Si under the highest magnetic induction should be described.

It should be mentioned why the leading phase changes from the Si phase to the Al phase under the effect of the rotational magnetic field.

The supporting information could not be downloaded at: www.mdpi.com/xxx/s1, Figure S1: title; Table S1: title; Video S1: title.

Author Response

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Reviewer 5 Report

This paper studies the effect of RMF on the Al-Si eutectic structure. The macro segregation, Si concentration distribution, and volume fraction of the samples were investigated. I think it can be accepted for publication.

Author Response

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Round 2

Reviewer 3 Report

I confirmed corrections of manuscript according to my comments.

The manuscript is accepted for publication as the present style.