Martensite formation in AISI 321 depends upon the chemical composition, SFE, Md30 temperature and % age of cold work. The Md30 temperature of a given AISI 321 steel according to the equation below is calculated as 9 0C.
Md30(OC) = 413 - 462 (%C + %N ) - 0.2 (%Si) - 8.1 (%Mn) - 13.7 (%Cr) - 0.5 (%Ni) - 18.5 (%Mo).
Pleas explain the possibility of formation of martensite at temperature higher than Md30. also comment about effect of heat produced during cold rolling as the on Md30 temperature?. Should the martensite form if working temperature exceeds many folds than Md30 (room temperature + heat produced during cold rolling)? If yes, please explain.
Well I didn't investigate AISI 321 but in case of AISI 304 (similar composition but without titanium) and after 0.45 of true strain during tensile loading at room temperature I have obtained ~6% of martensite. Md30 is a temperature at which 50% of austenite transforms into martensite after 0.3 cold deformation true strain so at higher temperatures martensite also is being formed but at lower quantities. Remember that this is only empirical formula do not believe those to much.
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