INFLUENCE OF COMPOSITIONAL BANDING ON GRAIN ANISOTROPY IN 3CR12 STEEL

The microstructural evolution of a 12 wt-%Cr steel (3CR12) during cooling from a solution heat treatment at 1380-degrees-C has been investigated. Emphasis has been placed on determining the microstructural factors responsible for the persistent occurrence Of grain anisotropy in this steel. Energy dispersive X-ray spectroscopy was used to determine the composition of the phases resulting from the solid state delta-ferrite to austenite transformation. It is shown that the high temperature delta-ferrite phase partially decomposes to austenite via a Widmanstatten growth mechanism and consequently a banded two phase structure is produced after hot rolling. The element partitioning, which arises during the solid state delta-ferrite decomposition, leads to irreversible compositional banding. An empirical model is proposed for the events leading to the generation of the banded phase structure and the formation of an elongated ferritic microstructure in 3CR12 after subcritical annealing.