Effects of Strain and Deformation Temperature on Bainitic Transformation in a Fe-C-Mn-Si Alloy

Abstract

The relationship between the strain corresponding to the maximum amount of bainite (termed as peak value strain) and ausforming temperature is investigated by metallography, X-ray diffraction, and dilatometry. The results indicate that the peak value strain increases with the increase of ausforming temperature, whereas the corresponding maximum amount of bainitic transformation decreases. Ausforming has dual effects on bainitic transformation, i.e., the promoted nucleation and the retarded growth. However, the retardation of bainite growth increases more quickly with strain, whereas the promotion effect by nucleation increases slowly. When the ratio of the promoted factor to the negative factor reaches the maximum, the amount of bainite also reaches the maximum. The volume fraction of retained austenite increases with a lower ausforming temperature, which manifests that the stability of residual austenite is enhanced at a lower ausforming temperature. In addition, a critical strain corresponding to a certain ausforming temperature exists, depleting the previously increased bainite amount to the same degree as the undeformed austenite.