The Role of Carbon Content on the Microstructure of Rapidly Solidified Fe–Cr–Ni Duplex Steels

In this research, the microstructure of three melt‐spinning ribbons with a weight‐based composition of Fe–25Cr–5Ni and varying carbon contents (0.02, 0.10, and 0.38 wt%) is evaluated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used for microstructural characterization. SEM analyses consist of image acquisition and electron backscatter diffraction. TEM analyses consist of bright‐field image acquisition, selected area electron diffraction, high‐resolution TEM, and local chemical composition measurements by energy‐dispersive X‐ray spectrometry. According to the results, the ribbons show different microstructures resulting from different solidification paths. The ribbon containing 0.02%C presents a predominantly ferritic microstructure, and austenite solid‐state precipitation is not suppressed. It occurs as grain‐boundaries allotriomorphs and secondary Widmanstätten side plates. As a result of carbon additions, the ribbon containing 0.10%C shows a microstructure composed of nearly equal parts ferrite and austenite, along with M 23 C 6 (M = Cr 15.6 Fe 7.4 ) nanometric carbides. The cube‐on‐cube orientation relationship is found between M 23 C 6 and austenite. Lastly, the ribbon containing 0.38%C exhibits austenitic microstructure with islands of ferrite surrounded by M 7 C 3 (M = Cr 4.14 Fe 2.86 ) carbides.