Effect of Cold Rolling and Molybdenum Content on the Kinetics of Spinodal Decomposition in Duplex Stainless Steels

This work analyzes the effects of cold rolling and aging treatment at 500 °C on duplex stainless steel 2205 and 2304 lean duplex stainless steel. Microstructural analyses are conducted using scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The mechanical behavior is assessed using Vickers microhardness and tensile tests. The samples are subjected to different aging periods ranging from 0.5 to 48 h at 500 °C, both in the as‐received condition and after cold rolling with a 74% thickness reduction. The primary objective is to detect spinodal decomposition in the samples and understand its influence on the mechanical behavior. Deformation‐induced martensite formation and spinodal decomposition are observed in the cold‐rolled samples. The characterization of the spinodal decomposition is based on the mottled appearance observed by TEM, which becomes more evident with longer aging times. During the aging heat treatment, both hardness and tensile strength increase significantly, although there is a corresponding reduction in ductility. Among the cold‐rolled samples, the increase in the mechanical properties is greater for the undeformed steels. Spinodal decomposition in deformed steels slows the ferrite recovery process by anchoring the dislocations.