SPINODAL DECOMPOSITION OF PRECIPITATION HARDENING Fe-17Cr-4Ni-4Cu STAINLESS STEEL AT 475 °C

Microstructure evolution and mechanical properties in an Fe-17Cr-4Ni-4Cu alloy aged at 475 °C after different aging times were studied. Conventional transmission electron microscopy (TEM) high-resolution (HREM) studies revealed the formation of 9R-structure Cu-rich precipitates Cr-rich α’ phase by spinodal decomposition samples 100–1000 h. The fine lead to a significant increase hardness, together early stages (100 h). Continued 500 h leads increased precipitation α’, which provides strengthening, reaching maximum hardening, despite continued loss hardening weakening Ostwald ripening precipitates. Extending time 1000 substantial reversed austenite transformation large number -copper that causes softening. results impact tests showed major fracture mode was cleavage and/or quasi-cleavage.