Influence of Deformability of Retained Austenite on Martensitic Transformation in Tension for Low Alloy Steel at Low Temperatures

摘要

The tensile properties and mechanical stability of retained austenite in a low alloy steel were evaluated at low temperatures. Transformation-induced plasticity introduced a good balance of strength and ductility at the temperatures from 193 K to 293 K. A high work-hardening rate in the initial stage of deformation and strengthening of the ferrite matrix by lowering the temperature were responsible for the good balance. The higher work-hardening rate at low temperatures was enhanced by the stress-induced transformation of retained austenite. At 0.1 strain over a temperature range from 193 K to 293 K, the retained austenite near a zone normal to was mechanically stable, where not only mechanical stability but also deformability in the retained austenite and austenite grain rotation with ferrite matrix strongly affected the martensitic transformation in the steel. On the other hand, at 77 K, almost all of the retained austenite was transformed to martensite regardless of its orientation because of its low phase stability.