In-situ observation of intragranular ferrite nucleation at oxide particles

"In-situ" real time observation of the ferrite nucleation at nonmetallic in clusions has been successfully made at elevated temperatures with a confoca l scanning laser microscope. The nucleation site, nucleation temperature, a nd/morphological change of the precipitates and ferrite can be sequentially determined as the phenomena occurring on the surface of steel. A polygonal ferrite starts to precipitate at an oxide particle at 1 010 K and a Widman statten ferrite starts to precipitate at a MnS particle at 967 K. The degre e of super cooling for austenite-ferrite transformation is found to be in g ood agreement with the prediction by a thermodynamic calculation.