Metastable ASS grades such as 304, 304L, 304LN, HNS, 201 etc., undergo large strain hardening during true plastic deformation (tensile). It is known that the higher strain hardening means large absorption of energy before failure which ultimately signifies the DIMT (deformation induced martensitic transformation) mechanism during plastic deformation. DIMT includes several transformation paths and twinning is one of them. Twins act as a precursor to DIMT and it occurs at high strain rate. However, I am unable to understand how the strain hardening behaviour of a particular metastable alloy under plastic deformation affects the twin formation!!!!!
Please enlighten me with your expert opinion and if possible with references.
Thank you.
I do not have the answer. However, the phenomena of conversion of non-magnetic austenitic 300 series SS to magnetic by cold working may provide some clue.
Dear Dr. Das,
Thank you for your advise.
Actually I used magnetic induction measurements for identifying ferromagnetic phases as an end product of tensile deformation. Several TEM analysis shows me that twining as well as dislocation pile-ups influences the DIMT process during plastic deformation. I observed that phase transformation (BCC or HCP phases) increases with higher plastic deformation and mainly governed by the formation of deformation twins. Twin boundaries are the nucleation sites of BCC or HCP phases during deformation. But the formation of twins due to strain hardening of a material during plastic deformation is unexplained which increases my concern.
Critical stress to form twins is rather high. That is why a notable stage of work hardening should be passed first. Nothing else.
Zisman the rights. Besides as martensitic transformation as well twining it a way of a relaxation of stress
Thank you Professor Zisman and Eterashvili for your valuable comments.
It means, at high flow stress (above critical level into the plastic domain) and true strain (>0.30) level, metastable ASS with low/moderate SFEs should produce deformation twins and it will increase with the increase in stress level.
Road Manidipto Mukherjee
Such processes not so simply to explain. Read books: Physical Metallurgy, Edited by R.W. Cahn 1965. To you it is the book will help.
Dear Mukherjee,
Formation of twins is not independent of dislocations. Its formal discussion is lenghty but initiation of twins closely related to formation of dislocations. And all that is tighly dependent on the SFE. The birth of both dislocations and twins progressively becomes easier as SFE reduces. ASS due to FCC structure have the capacity to create large deformations on numerous slip planes with number of dislocations. When slip planes become saturated with dislocations (this becomes easier with lower SFE) the system finally resorts to the additional deformation mechanism, the twinning. I hope I did not misinterpret your question and repeated things that you already know.
Best regards
Dear Dr. Kaya,
Thank you for your valuable comment regarding this topic. It helps me a lot. Further,I request you to provide me few references if possible.
Thank you once again,
With regards.
Thank you Professor Mirzadeh for your valuable comments and reference links. This should be very much helpful for my study.
Regards,
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