Decomposition of deformed ferrite in a duplex stainless steel

Abstract

The decomposition of deformed ferrite in a duplex stainless steel (U44L) has been examined using transmission electron microscopy. During annealing, austenite precipitation was extremely rapid and pinned the developing ferritic subgrain structure. Hence, the ferrite recrystallized via a continuous mechanism. Deformation of the ferrite, and to a lesser extent the austenite during growth/coarsening of the austenite, led to a ‘secondary recovery’ process. Subgrain coalescence, within the ‘primary’ ferrite subgrain structure and in the austenite particles, was observed after long term anneals: this process took place by the dissolution of the sub-boundaries formed during the secondary recovery process. In addition to the formation of austenite, M₂₃C₆, σ, and martensite were also observed.

MST/311