Mechanisms of transgranular carbide precipitation in deformed 304 stainless steels

Abstract

Transgranular (TG) carbides form in thermomechanically processed austenitic stainless steels (SS) when the material is plastically deformed to high strain levels, typically above 20%, and for heat treatments that lie within the 500-850°C sensitization range of the SS. In recent work, we have shown that the TG carbide precipitation is site-specific, and favors deformation-induced sites created during the straining process. Specifically, twin-faults and their intersections, and dislocation intersections have been indicated to be preferred sites forTG carbide formation in 304 and316 SS, while clustered regions containing a mix of fine-austenite and lath martensite were also observed to be critical sites for the TG precipitation in 304 SS. In this paper, we present lattice image observations of carbide precipitates in the TG fme-austenite/lath martensite regions of 40% deformed, 670°C/0.1-10h heat treated, 0.051%C 304 SS, as a means to understand the mechanisms of TG carbide precipitation in the SS.