Effect of Cu Content on Aging Precipitation Behaviors of Cu-Rich Phase in Fe-Cr-Ni Alloy

The precipitation characteristics and effect on strengthening mechanism of Cu-rich phases during short-time and long-time aging for Super 304H steels with different Cu content were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the size of Cu-rich phase particles increases, the interspace of Cu-rich phase particles decreases and the density of Cu-rich phases increases with the increase of Cu content during short-time aging (approximately 800 h) at 650 °C for Super 304H steels. During long-time aging (more than 2000 h) at 650 °C, Cu-rich phase precipitates sufficiently and the strengthening effect of Cu-rich phase is preferable in Super 304H steel containing Cu of 4%. The strengthening effect of Cu-rich phase in Super 304H steels containing Cu of 2.2% or 5% is weaker than that with Cu of 4% during long-time aging (more than 2000 h).