Nucleation During Recrystallisation in Ti-SULC Steel

This work is part of a PhD study which investigates mechanisms of nucleation during recrystallisation in steels. A specially built SEM with EBSD and heating stage allows us to observe static recrystallisation in situ. Changes in samples of Ti-stabilised ultra low carbon steel heated to 550ºC are documented via still images, videos and automated EBSD maps. Recrystallisation begins rapidly but slows down within an hour. A temperature increase to 850ºC forces complete recrystallisation. EBSD mapping shows that the ‘new’ grains appear first on the boundaries of deformed {111} grains and have high angle misorientations with the deformed grains, although the new grains are also of {111} type. {111} type deformed grains are recrystallised first due to their higher stored energy relative to {001} grains. Mapping of a section through the sample along the rolling direction reveals intragranular shear bands. Future work will look at these sites in more detail to determine their role as sites for nucleation.