Dynamically transformed ferrite fraction inferred from dilatometry measurements after deformation

A new method based on quantitative dilatometric analysis was proposed to measure the ferrite fraction formed during deformation in the austenitic region of low carbon steel. The dynamically transformed ferrite (DTF) fraction (fD) can be derived by fD = fT − fH, where fT is the total volume fraction of ferrite measured on the quenched specimen, which is subject to deformation and subsequent isothermal holding, and fH is the volume fraction of ferrite formed during the holding, which can be measured by using dilatometry. The DTF fraction derived by the new method was compared with that obtained by the conventional method of direct quenching. It is found that the DTF volume fraction obtained by the new method is smaller than that obtained by the conventional water quenching method, and the difference becomes larger at higher strain.