Effect of Cold Rolling on Phase Separation in 2202 Lean Duplex Stainless Steel

Abstract The effect of plastic deformation (cold rolling) on the thermal aging of a lean 2202 duplex stainless steel at intermediate temperatures (280°C–450°C) was studied using a combination of atom probe tomography and thermoelectric power measurements. In the undeformed condition, spinodal decomposition of ferrite was shown to be the prime aging process having an activation energy of 206 kJ/mol. The spinodal decomposition kinetics of ferrite increased with increasing deformation rate. Plastic deformation enhanced the aging and the austenite partly transformed into martensite. When no precipitation or phase transformation was observed in austenite, both ferrite and martensite decomposed. Martensite also decomposed at 450°C, via a nucleation and growth process, producing chromium nitrides, G-Phase, and epsilon Cu. The Fe–Cr-rich martensite was also shown to decompose but through a nucleation and growth mechanism, owing to a decrease of the Cr content in the matrix.