Mediating phase decomposition to avoid thermal aging embrittlement in a duplex stainless steel

Abstract

Due to the presence of miscibility gap in the body-centered-cubic structure iron‑chromium alloy system, the ferrite will decompose into the Fe-rich α phase and Cr-rich α´ phase, resulting in the inherent “475 °C embrittlement”. In this study, a pulsed electric field is introduced to mediate the phase decomposition for avoiding aging embrittlement. Combining nanoindentation testing and atomic-scale characterization, the results show that almost no aging hardening and phase decomposition behaviors occur with the pulsed electric field intervening, and the thermodynamic analysis indicates that the pulsed electric field can shrink the spinodal domain. Further, the life evaluation shows that the equivalent aging time of the duplex stainless steel is 18.2 years without the application of the pulsed electric field, while the equivalent aging time of the duplex stainless steel is 1.2 years under the action of the pulsed electric field, which is equivalent to an extension of the service life by 17 years. This study offers an opportunity for resisting the aging embrittlement process to prolong the longevity of components. • The ferrite decomposition is suppressed by pulsed electric field during thermal aging. • Spinodal decomposition plays the major role in thermal aging embrittlement. • Pulsed electric field induces the spinodal domain to shrink for avoiding phase decomposition. • The equivalent service life of duplex stainless steel is extended by 17 years.