The characterization of G-phase in Fe20Cr9Ni cast duplex stainless steel

摘要

The G-phase with a cubic morphology in a Fe20Cr9Ni duplex stainless steel was found after thermally aged at 475 °C for different times in this study. The microstructural evolution, crystal structure and composition distribution of the G-phase were studied by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) in this study. The experimental results showed that the morphology of the G-phase was mainly controlled by the misfit degree between the matrix and the G-phase. Moreover, the growth of G-phase was confirmed to be in accord with the Ostwald ripening mechanism. During its growth, the Cr element in the matrix partly replaced the Si and Mn elements in the G-phase, resulting in a change in the intensity of the (400)_G spot of the G-phase. With the extension of thermal aging time and the growth of G-phase, the original periodic of the G-phase was destroyed and the super structural change took place in this duplex stainless steel.