Unveiling the role of cerium in enhancing the hot ductility of super austenitic stainless steel S32654 at different temperatures

Abstract

The role of cerium (Ce) in enhancing the hot ductility of super austenitic stainless steel S32654 at 850–1250°C was systematically unveiled through theoretical calculations and microstructure characterization. The results indicated that Ce microalloying improved the hot ductility of S32654 throughout the entire deformation temperature range. Specifically, the addition of Ce greatly enhanced the hot ductility in the low (850–900°C) and high (1100–1250°C) temperature ranges, but only slightly increased that in the medium temperature range (900–1100°C). At 850–900°C, Ce addition not only reduced the sulfur (S) content and suppressed the S segregation at the grain boundary, but also promoted the formation of slip bands and deformation twins, apparently improving the hot ductility. At 900–1100°C, Ce addition promoted the nucleation of intergranular σ phases and dynamic recrystallization (DRX) grains, which have adverse and beneficial effects on the hot ductility, respectively. As the temperature increased, the precipitation tendency presented a first increasing and then decreasing trend around 1000°C, while the DRX gradually increased. Accordingly, the improvement degree of Ce on the hot ductility first weakened and then enhanced. At 1100–1250°C, Ce significantly promoted the DRX to form more fine and uniform deformation structure, thereby remarkably increasing the cracking resistance and then the hot ductility.