When you have a determined % of martensite (because you did not get to the Mf temperature in quenching), the diagram tells that lowering temperature will transform the remaining austenite into martensite, but would that transformation not require fast cooling?
If you cool down below the Mf-temperature, the austenite will transform into martensite. Quenching is only required, if the Mf is high enough to enable diffusion and therefore a transition of austenite and martensite into ferrite and carbide. At lower Mf temperatures, the cooling rate has not a high influence.
Martensitic transformation is diffusionless, athermal in nature i.e. % of martensite formed w.r.t the transformation temperature is constant and cannot be altered by varying the quenching severity.
Ms and Mf temperatures are definite for a given steel. However cold working or addition of alloying elements will affect the Ms temperature.
Thank you both for answering. I think I found an answer. I am sorry I did not expose my concern clearly.
What I found out is that there is some temperature (name it Ms': the restart martensitic transformation temperature) at which you would have to set the steel to allow retained austenite transform to martensite, after an incomplete temple. You could also do it by plastic deformation.
I hope I made it clear, where I am really is in the "subzero temple" concept.
Please tell me if there is something I am stating wrong
You are not so wrong.. Please focus on "IF" used in T. Fiedler's comment. Actually for most martensitic steels,, if the intermediate (Ms
More exact explanation on my previous comment... Exposure at intermediate Mf
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