Dear Rasoul,

The amount of sulphur within your samples is well above the conventional treshold values (< 0.03%) suggesting that the addition of S has been done on purpose probably to allow a easier subsequent machining at a high speed due to the presence of large amount of sulfides (MnS).

So you may consider the elaboration process of each alloy first, as MnS (inclusions) are known to be malleable at high temperature, during forging for example.

If the same forging ratio is achieved on both alloys, and if all the sulphur has been fixed with Mn to form MnS, then you should observe a higher amount of MnS within the alloy containing 0.06% of S compared to the one that only contains 0.02%. This can be done in the as-polished condition under light microscopy and if possible, you can easily perform a quantitative assessment of the MnS inclusions content in both aloys. The MnS should be more easy to observed in a direction parallel to the rolling axis (elongated or rod-shaped, with a light grey contrast under optical microscope). Do not try to check for MnS presence after etching!

You may also try to check for the exact chemical composition to be sure that the expected sulphur content is really that of the actual samples. You may aslo pay attention during the metallographic preparation (grinding and polishing) so to avoid pulling out the MnS because they are softer than the matrix.

Dear Jerome Tchoufang Tchuindjang 

I really appreciate you comprehensive and expert comment. Thank you very much

Dear Rasoul,

you can see differences only in amount of MnS (non metallic inclusion) in your metallographic images. Like mr. Jerome says, you should perform testing in  a direction parallel to the rolling axis (elongated or rod-shaped). It is standard procedure (ASTM E 45 or ISO 4967). The difference will be obvious: more sulfide will be in alloy with 0,06 %S. 

Good luck

Thank you very much