Complex isothermal precipitation behavior of V(C, N) in V-, N-added low carbon steel

Abstract

Precipitation behavior of carbide/carbonitride in high-strength low-carbon steel is significantly affected by the ferrite transformation modes, which may change from the negligible partitional local equilibrium mode to the partitional local equilibrium mode as holding temperature increases or holding time increases at a certain temperature for ferrite phase transformation. Herein, the isothermal precipitation behavior of V(C, N) under negligible partitional local equilibrium mode of ferrite transformation in V-, N-added low carbon steel has been investigated. Not only the complex precipitation coexisting phenomenon of random precipitation and fibrous precipitation but also that of random precipitation and interphase precipitation was observed and certificated by the selected area electron diffraction patterns. In addition to Baker–Nutting orientation relationship, the Kurdjumov–Sachs OR [111]α//[110]P, $$\left( {1\overline{1}0} \right){\upalpha }//\left( {1\overline{1}\overline{1}} \right)$$ P between ferrite and interphase precipitation were found. Due to big variation in the movement velocity of austenite/ferrite interface, non-uniform distribution of precipitates occurred, resulting in hardness of ferrite grains changing from 185 to 215 HV.