Martensite Formation from Reverted Austenite at Sub-zero Celsius Temperature

Inter-critical annealing of soft martensitic stainless steel leads to formation of fine-grained reverted austenite, which is stabilized by partitioning of Ni. Generally it is reported that reverted austenite is not affected by immersion in cryogenic liquids, such as boiling N2 and He. The present data show that reverted austenite that is apparently stable at boiling nitrogen temperature does transform isothermally to martensite during holding at 195 K.

The results are explained in terms of thermally activated martensite formation.