Evolution of Microstructure and Fe/Fe₃C Interface Structure in Cold‐Drawn Pearlitic Steel Wires

Abstract

The microstructure, texture, and dislocation configuration of cold‐drawn pearlitic steel wires were investigated by scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). In addition, Fe/Fe3C interface structure at the atomic level was clearly observed and analyzed by high‐resolution TEM (HRTEM), and the microscopic deformation mechanism of cementite lamellae at different drawing strains is revealed. The results show that pearlite lamellae turn to the drawing direction to form ferrite <110> fiber texture, and the cementite and ferrite lamellae are simultaneously thinned with the increase of drawing strain. During the cold drawing process, shear‐bands(S‐bands) are formed in the cementite lamellae; the dislocation of ferrite transits from single slip to multi‐slip stage, and the dislocation density increases. After drawing, the lattice structures of cementite and ferrite phases show the evolution from single‐crystal to polycrystal, and the cementite lamellae are divided into a multilayer structure: central relative large‐size cementite crystal and outside relative small‐size cementite crystal layer; the dissolution of cementite lamellae in some regions results in the lattice expansion of ferrite phase and the occurrence of neck‐down regions in the cementite lamellae.

Molecular dynamics study on the effect of cementite structure on the mechanical properties of pearlite

“…Due to its excellent mechanical properties such as high strength and good ductility, pearlitic steel wires have been widely employed in important engineering fields such as bridge cables, automotive tire steel cord, and cutting wires [1,2]. These wires are manufactured by subjecting hot-rolled steel rods to multiple cold drawing processes, resulting in a rapid increase in strength with the increase in cold drawing strain.…”

“…These wires are manufactured by subjecting hot-rolled steel rods to multiple cold drawing processes, resulting in a rapid increase in strength with the increase in cold drawing strain. Research has shown that the strengthening mechanisms of pearlitic steel wire during the cold drawing process can be attributed to three aspects [3,4]: (1) The interlamellar spacing decreases with the increase of cold drawing strain, resulting in fine grain strengthening and the relationship between interlamellar spacing and strength can be described by the Hall-Petch equation; (2) Dislocations in the pearlite increase rapidly during cold drawing, leading to dislocation strengthening; (3) The dissolution of cementite occurs during cold drawing, and the dissolved carbon atoms diffuse into the ferrite, resulting in solid solution strengthening.…”

“…As known above, multiple changes in the internal structure of pearlite occur simultaneously during the cold drawing process, and the alteration in mechanical properties arises from the combined effect of these structural variations. Previous researchers have primarily relied on experimental methods to investigate the evolution of microstructure and performance of pearlite steel wires during cold drawing, but these methods are unable to separately examine the influence of cementite structure transformation on the mechanical properties of pearlite [1][2][3][4]. Molecular dynamics (MD), as a simulation research method, provides a unique opportunity to study material properties under desired conditions [8,9].…”