Atom probe tomography characterization of heavily cold drawn pearlitic steel wire

Atom Probe Tomography (APT) was used to analyze the carbon distribution in a heavily cold drawn pearlitic steel wire with a true strain of 6.02. The carbon concentrations in cementite and ferrite were separately measured by a sub-volume method and compared with the literature data. It is found that the carbon concentration in ferrite saturates with strain. The carbon concentration in cementite decreases with the lamellar thickness, while the carbon atoms segregate at dislocations or cell/grain boundaries in ferrite. The mechanism of cementite decomposition is discussed in terms of the evolution of dislocation structure during severe plastic deformation.

Research Highlights
► Cementite lamellae have not completely decomposed after a true drawing strain of 6.02.
► Carbon concentration in ferrite saturates at high strain.
► Carbon concentration in cementite varies proportionally with the lamellar thickness.
► The decomposition of cementite is presumably controlled by carbon–dislocation interactions.
► Carbon atoms are segregated at cell/grain boundaries or individual dislocations in ferrite.