Effect of grain size on transformation-induced plasticity in an ultrafine-grained metastable austenitic steel

The stress–strain curves and temperature change of ultrafine-grained (UFG) austenitic steels with different grain sizes were measured during uniaxial tensile testing. The uniform stress–strain and temperature change curves are divided into three different regions depending on the hardening mechanisms. The strain-induced martensite in the UFG steels provides extra-strain hardening, large ductility and slower temperature increase. The critical stored energy for the formation of the strain-induced martensite is measured as a function of austenite grain size.