The Effects of Iron-Bearing Intermetallics on the Fitness-for-Service Performance of a Rare-Earth-Modified A356 Alloy for Next Generation Automotive Powertrains

Round 1

Reviewer 1 Report

The manuscript titled “The Effects of Iron-Bearing Intermetallics on the Fitness-For-Service Performance of a Rare-Earth-Modified A356 Alloy for Next Generation Automotive Powertrains” investigates the effects of Mg and Mn concentrations on the phase formation and high-temperature mechanical properties of a novel A-Si alloy with REE additions, utilizing tensile and creep experiments at 250 ^oC as well as thermodynamic calculations and metallographic investigations. Authors demonstrate that by carefully adjusting the Mn and Mg concentrations a complete transformation of the brittle beta and pi phases into the alpha phase with a relatively higher ductility can be achieved, which leads to significantly better mechanical properties.  

This is an extremely well-written and important manuscript and of great interest to the research community and the readership of Metals. Results are presented beautifully and support the main conclusions of the paper. Thus, I highly recommend publishing the manuscript.

A minor correction:

In several places in the manuscript including the abstract, the word “load” has been used instead of “stress,” which should be corrected.  

 

 

 

 

Author Response

Thank you very much for nice comments!

We have addressed you comment by correcting the term "load" to "stress".

Thank you

Reviewer 2 Report

I would like to found more general bibliography, because a reviewer can not be always deep in the specific  subject, and in particular for what concerns experimental detail. An extended bibliograpy, mainly for the general part, make too simpler this worrk,  and  improving understanding

Author Response

Thank you for your comments. We have made an effort to ensure that the paper provides sufficient information on the specifics of our test and refers the bibliography that connects with applicable standards and fundamental principles of the testing.

Reviewer 3 Report

The study aimed to improve the tensile strength and creep resistance of a rare earth-modified A356 alloy by modifying the Mg and Mn concentration in the alloy. Influence of  Mg and Mn elements on microstructure of the alloy was studied from both thermodynamic simulation and experiments. The elevated temperature tensile and creep performance of two alloys were conducted and evaluated. The results and discussion are convincing. I’d like to suggest publication of the paper with minor improvements as follows:

1. In the “2. Experimental Procedure” session, please add how the concentration of Mn and Mg elements was adjusted or how the two alloys, namely A356RE-A and A356RE-B, were made.
2. For the influence of Mn and Mg elements on the AlSiRE phase in the two alloys, the comparison of optical micrographs(Fig.7 and 9) and SEM micrographs(Fig. 8 and 10) are not clear enough to draw the conclusion on the AlSiRE phase

 

 

Author Response

Thank you for the comments and suggestions! Below includes adjustments for your comments.

1. The experimental procedure has been adjusted to include the appropriate information about how the Mn and Mg concentrations were adjusted. The following statement was included in the paper:

“To modify the concentration of elements in the A356RE-B alloy, an Al-25wt.%Mn master alloy was introduced to the alloy melt”

2. The authors are assuming that the conclusion that reviewer 3 is referring to is with regards to the transformation of the plate-like AlSiRE phase to Script AlSiRE. Based on this assumption, the authors have re-labelled the SEM micrographs to more clearly differentiate the two morphologies.

In addition, the following statement has also been included in the article:

“In the A356RE-A alloy, the AlSiRE phase was observed to form predominantly with the plate-like morphology (~90-95%), whereas the plate-like morphology was present in less than 5% in the A356RE-B alloy.”