Sigma stringers or delta ferrite stringers? 2

[Naruwan]

Hi guys,
I have a problem identifying the 'foreign' structure in this 316L heat affected zone. Attached is a photo-micrograph of a SS316L HAZ at 500X. I had used 10% Oxalic acid to etch the structure and found out there's strange structures which looked either like sigma phase or delta ferrite. I know the dark round spots are carbide, but I just can't be sure about the stringers.

Thanks in advance!

 

[stanweld]

Looks like ferrite.

 

[metengr]

Agree. Looks like delta ferrite.

http://www.buehler.com/technical_information/Buehler Book/etching.pdf

 

[EdStainless]

The clue for me to call this dF is the rounded globular look, and the fact that they are not associated with other parts of the structure (Sigma normally forms along other features).

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Plymouth Tube

 

[Guest102023]

The morphology is consistent with ferrite.