Fine-scale microstructural investigations of warm rolled low-carbon steels with and without Cr, P, and B additions

Carbide formation, solute clustering, and solute segregation to dislocations and boundaries were studied in warm rolled, low-carbon steels. Transmission electron microscopy and atom probe tomography (APT) were employed on materials with and without Cr, P, and B alloying additions. These investigations revealed C and P segregation to the ferrite boundaries and depletion in Mn and in some cases in Cr. The exact nature of the solute segregation depends on the composition of the steel and the nature of the boundary. The formation of fine C-Cr-Fe clusters (15-50 atoms) in all the steels was detected by APT. A detailed analysis of the Cottrell atmospheres formed on multiple dislocations was performed using APT. Atmospheres containing C atoms were observed in all the steels. Some weak P segregation to dislocations was also detected in the Cr-P alloyed steel.