The mechanical stabilisation of Widmanstنtten ferrite

Mechanical stabilisation is a phenomenon in which displacive transformation is retarded when it occurs from a parent phase which is plastically deformed. Compression experiments, in which plastically deformed austenite was allowed to transform to Widmanstنtten ferrite, have revealed that like bainite and martensite, Widmanstنtten ferrite is also susceptible to mechanical stabilisation. The amount of Widmanstنtten ferrite that could be obtained decreased when the austenite was deformed, as growth became hindered by the accumulated debris of dislocations in the austenite. The microstructure nevertheless became refined as the number density of nucleation sites was increased by the deformation process. Severe deformation eventually led to a recovery in the maximum attainable quantity of Widmanstنtten ferrite, because of an overriding effect of the increased nucleation rate. The results are shown to be consistent with the growth of Widmanstنtten ferrite occurring by a displacive mechanism.