Temperature dependence of precipitation mechanism of intragranular χ phase in super duplex stainless steel S32750

•The precipitation mechanism of χ phase was temperature dependent.•Lenticular χ phase homogeneously nucleated after aging at 650 °C.•Granular χ phase utilized Cr2N as preferential nucleation sites after aging at 800 °C.•The interface coherency and orientation relationships between χ phase and ferrite matrix were different.•Driving force was responsible for precipitation mechanisms of χ phase. 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.