Effect of Processing Schedule on the Microstructure and Texture of 0.78 wt% Cr Extra-low-carbon Steel

Abstract

An extra-low-carbon steel was alloyed with 0.78 wt% Cr and subjected to three different processing schedules involving: (i) warm rolling to 65% reduction at 640°C, (ii) warm rolling to 80% reduction at 580°C and (iii) warm rolling to 65% reduction at 640°C followed by cold rolling to 40% reduction. Increasing the severity of the deformation resulted in an increase in the number of grains containing in-grain shear bands. X-ray bulk texture analysis indicates that the γ-fibre intensity was slightly higher in the steel warm rolled at 580°C than at 640°C and after cold rolling. Transmission electron microscopy and atom probe tomography revealed that Cr carbides were formed after all processing schedules. Carbon segregation to dislocations was also observed. Although the addition of 0.78 wt% Cr produced a volume fraction of carbides that was three orders of magnitude higher than those previously observed in 0.48 wt% Cr steels, a significant amount of solute Cr remained confined in the matrix and did not lead to any further depletion of the solute carbon.