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

Two types of precipitation mechanisms of intragranular chi 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 chi phase homogeneously nucleated within ferrite grains after aging at 650 degrees C. On the other hand, Cr2N provided heterogeneous nucleation sites for intragranular chi phase when aging at 800 degrees C, and displayed a granular morphology. The lenticular and granular chi phase have different interface coherency and orientation relationships with ferrite matrix, respectively. The difference in driving force for nucleation of chi phase at different temperatures was responsible for the different precipitation mechanisms. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Two different precipitation mechanisms of intragranular chi phase in super duplex stainless steel were investigated at different aging temperatures, with lenticular chi phase nucleating homogeneously within ferrite grains at 650 degrees C and Cr2N providing heterogeneous nucleation sites for granular chi phase at 800 degrees C. The driving force for nucleation at different temperatures was responsible for the observed differences in precipitation mechanisms.