I am seeking a conceptual understanding of how SFE could affect non-deformation properties of an alloy, such as (but not limited to) possible changes in phase transformations, precipitation, corrosion behaviour, solidification path, melting point etc. This is not material specific, so experiences from any material system are greatly appreciated. Literature references will be very helpful too.
Thank you very much!
Changing the mechanical, technological and physico-chemical properties in the evolving period of technology and processes allows for the realization of better materials with guaranteed performance parameters. Vacuum technologies have a strong influence. You create work environments that change SFE and create conditions for controlled processing. Conditions for controlling the process and major changes in the mechanical and chemical properties of the surface material are created.
Hi,
there is a lot of literature of SFE for stainless steels AISI 304(L) and 316(L). I'm sorry I don't have them at hand for the moment. Maybe you can check for them.
The influence on corrosion and phase change are well known. You must always consider that SFE is a thermodynamical effect in the crystal lattice and therefore you have energy differences in the SFE and your "perfect" lattice next to the SFE. And because a lot of other properties depends on this energy, there sould be differences. The question is just how big these differences are and if they are possible to measure within a certain accurancy.
I think you can have SFE influencing the physical metallurgical properties does happen provided the material/alloy has the relevant alloying elements which have tendency to react and form carbide residues at grain boundaries.
Thank you very much for your answers!
Dr Yankov - thank you for an interesting, though not directly related idea. If I understand correctly, you are suggesting that SFE may change due to pickup of various elements from the environment? I will look into this possibility.
Dr. Biehler - thank you, it was heartening to read that there is indeed a correlation. I agree with your conceptual explanation that the stacking fault ribbon is thermodynamically different from the remaning crystal. It would be informative to read some work that has been done in this regard. So far the literature I have gone through (on SS304/316 and other materials) has been either related to : (1) determination of SFE, (2) effect of various elements on SFE, (3) influence of SFE on deformation parameters. I have not come across literature related to corrosion/phase transformation. Since you have seen some of this work, I would be greatly indebted if you could recollect any information that could help find it, such as the authors/institute/paper titles etc. Thank you once again!
Thank you Dr. Polishetty! You have hit the nail on the head; elements forming precipitates or segregating at interfaces is a big part of what I'm interested in. I am not able to reason out whether a higher SFE would cause more or less segregation, could you help me out with this? Or is it not a simple correlation and will it depend on the individual elements, crystal structures etc?
I need to check for that... If Ihave something correlated to that topic, I'll let you know :-)
Dear Aashranth,
Needless to say that my answer will inevitably be conceptual.
SFE cannot change the melting point. Aluminum has a higher SFE value compared to magnesium and copper, and has almost the same melting point as magnesium but a much lower Tm than Cu. Copper on the other hand has the lowest SFE value among the three but it has a higher melting point than the other two. So the SFE values of metals do not immediately compare their melting points.
Yes, SF is a plane where not the coordination of the atoms but only the bond angles are different as compared to a perfect stacking order, we cannot realistically expect that the presence of SFs make a detectable change in the Tm for the same alloy either. If for nothing else, for the simple fact that by the time the Tm is reached under a normal heating regime as crystal defects should do (except the vacancies – their number would be maximum near Tm) at least most of SFs would be annealed out anyway.
And I do not think that a conclusive and straight forward answer can be offered regarding the relationship between the reactivity (e.g. corrosion) and the SFE. The only tentative comment in this sense has already been given by Biehler’s response above.
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