LAUSR

Abstract Two types of precipitation mechanisms of intragranular χ phase were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) in super duplex stainless steel S32750 at different aging temperatures. Results showed that lenticular χ phase homogeneously nucleated within ferrite grains after aging at 650 °C. On the other hand, Cr2N provided heterogeneous nucleation sites for intragranular χ phase when aging at 800 °C, and displayed a granular morphology. The lenticular and granular χ phase have different interface coherency and orientation relationships with ferrite matrix, respectively. The difference in driving force for nucleation of χ phase at different temperatures was responsible for the different precipitation mechanisms.