Fracture Behavior of AlMg4.5Mn Weld Metal at Different Temperatures under Impact Loading

Round 1

Reviewer 1 Report

Paper analyses  three-component aluminium alloy AlMg4.5Mn that has been welded 8 by using GTAW process in the shielded atmosphere of Ar+70%He+0.015%N2. The weld metal 9 toughness was evaluated at three different temperatures by using the instrumental Charpy pendu-10 lum impact testing, to measure not only the total energy, but also crack initiation energy and crack 11 growth energy. Fractographic analysis of fracture surfaces and the EDS analysis of large second 12 phase particles on fractured surfaces at each temperature were also carried out.

 

Paper title is adequate with paper content.

Methodology presented in paper is adequate.

Conclusion is well written and in line with methodology presented.

 

Reference are modern and adequate. 

Author Response

Please see the responses to your valuable comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is dealing with the analysis of the fracture behaviour of welded AA5083 aluminium alloy plates. The toughness of weld metal was evaluated at different temperatures using instrumented Charpy pendulum impact test. Total impact energy, crack initiation and crack growth energy were evaluated from Charpy tests which were supplemented with fractographic analysis of fracture surfaces and with EDS analysis of second phase particles. Authors have found good correlation between absorbed energy and fracture surface morphology.

The conclusions derived from the experiments are logic and valuable within the given content frame, but some further information would improve the value of the paper.

Authors correctly state that „From the point of view of material heterogeneity of welded joints, it is of utmost importance to know not only total impact energy, but also energies for crack initiation and propagation in base metal (BM), weld metal (WM), heat-affected-zone (HAZ), to get better insight in overall behaviour under impact loading (Row 70-73)”. The paper is containing only the analysis of WM, and tests of HAZ and BM are missing. At least the fracture behaviour of BM would be informative as reference value, compared with the analysed WM. This would characterise the effect of welding on the toughness. For example, a paper (Chuanjun Huang et al 2017 IOP Conf. Ser.: Mater. Sci. Eng. 279 012002) gives 22 J total impact energy for this alloy at T=-196 ^oC in BM, which is significantly higher, than the measured total energy (~8 J) in this paper for WM. Obviously, the two samples are not perfectly comparable, this is why measurement result of BM would be necessary.

Minor remark, that Figure 1. contains the shape of Charpy test specimen, but only a few words mention that the notch is located in weld metal (Row 114). It is understandable, but it might be useful to show the exact location of specimen in the welded plate. (For example with an added Fig. 1.b.)

Row 151: WM is correct instead of Wm.

Author Response

Please see the responses to your valuable comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper contains a very good review of the literature.

 

The manuscript must contain a list of symbols, abbreviations and markings. Please add nomenclature.

Please indicate the source for data on chemical composition - whether the authors determined it themselves - if so, please describe the procedure.

Figure 1 should show the location of the notch in the weld. The weld should be marked on the figure, it should be dimensioned, the preparation of the plates for the welding process should be shown, the approximate heat affected zone should be shown along with its dimensions.

The paper should include information on the mechanical properties of the alloy (yield strength, tensile strength, corresponding deformations, Poisson's ratio, parameters of the strain hardening curve according to the Ramberg-Osgood law). The authors should add such information, show the specimen they used for research - at least three tests should be carried out, and preferably more, and a statistical evaluation of the results obtained should be made. The same applies to the material already obtained after welding. Specimens for the static tensile test should be cut out of the welded plate, at least three tests should be performed, preferably even more, the force vs. displacement curves should be compared, the tensile curves sigma=f(epsilon) for both types of specimens. Authors should show the scater of results in the paper. The manuscript should show the shape of the specimens, especially those with a weld, it should show how both types of specimens broke. Unfortunately, this is not in the paper and it reduces its value.

When testing the impact strength of the welded alloy, the impact strength of the unwelded alloy - without a weld - should be assessed first. Such a test should be comprehensively planned, for the appropriate number of specimens for each of the temperatures considered by the authors - I believe that three speciemens in this case is definitely not enough - the scatter of impact strength results is quite significant. I would recommend testing with multiple specimens, comparing the results statistically, evaluating the scatter, evaluating changes in the brittle-plastic transition curve, as is done in the case of steel. You can also adopt here the analysis methods presented in the FITNET procedures by the team of prof. Kocak. The same analysis shall be performed for specimens prepared from welded elements. There must be lots of specimens here too.

While Figure 2 is acceptable, Figures 3 and 4 are of poor quality. It is not known whether these are figures prepared by the authors or taken from literature. Are these the results obtained by the authors - no values, no units.

It is incomprehensible to me how the authors calculate energy - they indicate in lines 158 that energy is calculated under the graph of force versus time - it is not logical - a fundamental factual error. Energy can be counted under the force vs. displacement graph. This completely disqualifies the manuscript from publication.

The authors do not mention how many tests they performed for each temperature. Conclusions cannot be drawn on the basis of three tests - one for each temperature. This is unacceptable. In Figure 6 there are curves, which do not know what they mean - this is not how you can present test results.

The manuscript cannot be published in its current form. I recommend thorough corrections and supplementing the research part with the elements listed above. Currently, I am in favor of rejecting the paper, its solid improvement, supplementing it with all the elements listed above. Only then can it be resubmitted for review.

Author Response

Please see the responses to your valuable comments in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

There were significant improvements in the text, I agree with them.

Reviewer 3 Report

All my suggestions were included by the authors in the revised version of the manuscript. I recommend the paper for publication.