Microstructural Characteristics of AlSi9Cu3(Fe) Alloy with High Melting Point Elements

Round 1

Reviewer 1 Report

METALS revision Comments on paper named “Microstructural characteristic of AlSi9Cu3(Fe) alloy with high melting point elements”- metals-920076-peer-review-v1 

General Comments: This paper follows, or is based, on another one from the same authors and used as reference (3) where there is used DTA techniques to supposed support the claim of sequential formation of different microconstituents and phases, only based on assumptions that some critical points on the derivative of cooling curve are this and that microconstituent, when to achieve that conclusions it ought to “freeze” the solidification sequence on the point of interest doing a quenching and undoubtedly showing that such a constituent is present at that particular temperature. Assumptions are not valid scientific options.  So, is doubtful some of the conclusions. More, the sample used to draw these suggestions is na open cup, which the final volume cannot be controlled, though the sensible heat might vary from sample to sample. 

The chemical phase analysis is a known and sound technique used by these researchers. 

Going to the global writing of the paper: 

1.  For instance, in line 50, 170 and at least 215, authors address the Chinese Script microconstituent or phase as “Chinese Writing”, but they address correctly in line 78 and 236, so a common classification should be used.  
2. Line 118 is written “this article presents” but the regular name is paper. 
3. Line 137 table 2 is split in two pages. 
4. Line 146 – is not common to use and pour Al alloys at a such aso large superheating temperature of 1000 C. 
5. Line 164 about thermal effects on the derivative cooling curve, and after studying reference [3], it is concluded that authors assumed, without an unbiased scientific proof, that the inflections are related to the precipitation of tertiary and quaternary eutectics. In order to improve the quality of this discussion, authors could provide more fundamental arguments why they consider those inflections as a sign of that precipitation, considering that the amount in the structure is very small to release heat enough to inflect the cooling rate trend. 
6. Figure 2 is in a very small amplification to allow the clear presentation of what authors call ternary and quaternary eutectics. These claims are not supported by experimental evidence. The figure is on a page with the legend on another one.   
7. What is resin sand? Is it furanic self setting sand or, as supposed, shell sand? 
8. Figure 10 is split in two pages. 

Final comment: authors made a correlation between the multi-phase with high melting point alloys but, in my opinion, assumed the precipitation of some tertiary and quaternary eutectics which does not have valid scientific demonstration. The lab technique is good but assumptions are doubtful. 

Author Response

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Reviewer 2 Report

Why was the chemical composition of the alloy used in the tests not checked by the authors, but read from the EN AC-46000 standard?
Figures 3, 4, 8, 9 - poorly visible descriptions in the drawings.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript describes a systematical investigation of the effect of Cr, Mo, V and W on microstructures of AlSi9Cu3(Fe) alloys. The microstructures were investigated using alloys having single or combined additions of the above elements as well as using two different solidification rates with HPDC and sand casting. It is not recommended for publication in the current manuscript due to several major and minor comments as follows.

• One of the most difficult things in this manuscript is descriptions of microstructures without exact information of the alloy compositions and additional amounts of those high melting temperature elements of the samples. What is the actual alloy composition of the base alloy in this study? Table 1 shows only a specification of alloy, within EN AC-46000. In addition, what is the actual additions of the high melting point elements and the actual alloy compositions used in this study? What does it mean “volatility jump” in this context? All in all, it is not clear in the manuscript and difficult to follow what and which compositions were actually investigated and discussed. Please specify the actual alloy compositions of the base alloy and of the alloys having high melting point elements used for the investigation.

• The Mn effect on Fe phases is described quantitatively, more/less than 0.15 wt%, in page 2 line 57-59. However this depends on solidification rate. What is the reference or base of these sentences? Also some discussion of composed phases after solidification depends on solidification rates.
• What is the acceleration voltage used in this study for SEM and EDS analysis?
• The presence of <beta> Al5FeSi is detrimental not only for mechanical properties but also for die soldering after casting in HPDC. As the problem is well known in HPDC industry and one of the reasons of Mn (and could be the others in this study) addition is to improve die soldering, it would be better to mention this aspect as well.
• The master alloys were used for addition fo Cr, Mo, V and W. What is holding time at about 750 degree C? and what do the authors think about dissolution rates of those elements into the melt?
• Do you have information of solidification rate for both the HPDC and the sand casting? Even a rough indication (or e.g. typical/average dendrite arm spacing) will be helpful to make the results more meaningful, since the resultant microstructure depends on solidification rates.
• Some figures can be better, e.g. it is difficult to see scale bars. Also, lack of information in some figures, e.g.” intensity” in vertical axis in Figure 4, “X-ray energy” in Figure 3. It is recommended to check all the figures to be better in the manuscript.
• In page 8 line 232, it is written “The presented data shows the presence of a solid solution <Alfa>Al…”. However the presented data can show <Alfa>Al, but not solid solution. Solid solution of what?
• What is the definition of “surface fraction”? In general, it is called “area fraction” of intermetallic in two demential picture analysed.
• In general, the process is called “solidification”, not “crystallization” in general term in this field. E.g. solidification path, solidification interval, etc.
• It would be better to write the results of sand casting and HPDC separately, e.g. different sub-sections. Plus, what is the conclusion in this study? “Conclusions” should be concisely written in a separate final section. All in all, it is not straight to follow the results in the manuscript. This is a recommendation of purely writing (not in science).

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

The manuscript was revised accordingly based on comments from of reviewers.