bhadeshia123 | Widmanstätten ferrite @bhadeshia123 | Uploaded February 2022 | Updated October 2024, 3 hours ago.
The nature of Widmanstätten ferrite in steels is described, beginning with the definition of a "crystallographic grain size" that controls the path of la propagating cleavage crack. This is followed by a description of the atomic mechanism of transformation, in essence a carbon diffusion-controlled displacive mechanism in which the composition of the ferrite is given by paraequilibrium with the austenite.
The lengthening rate of the plate of Widmanstätten ferrite is derived and shown to be consistent with experimental measurements. The idea that the plates are a consequence of interfacial instability in a carbon diffusion-field, as modelled using phase field theory is dismissed, one reason being that Widmanstätten ferrite is found in many interstitial-free alloys.
Finally, there is a rationalisation of the shear transformations in steels (martensite, bainite and Widmanstätten ferrite), revealing that not all three occur in all steels.
This series of lectures is organised by Professor Fabio Miani of the University of Udine in Italy.
Associated teaching materials can be found on:
phase-trans.msm.cam.ac.uk/teaching.html
H. K. D. H. Bhadeshia
The nature of Widmanstätten ferrite in steels is described, beginning with the definition of a "crystallographic grain size" that controls the path of la propagating cleavage crack. This is followed by a description of the atomic mechanism of transformation, in essence a carbon diffusion-controlled displacive mechanism in which the composition of the ferrite is given by paraequilibrium with the austenite.
The lengthening rate of the plate of Widmanstätten ferrite is derived and shown to be consistent with experimental measurements. The idea that the plates are a consequence of interfacial instability in a carbon diffusion-field, as modelled using phase field theory is dismissed, one reason being that Widmanstätten ferrite is found in many interstitial-free alloys.
Finally, there is a rationalisation of the shear transformations in steels (martensite, bainite and Widmanstätten ferrite), revealing that not all three occur in all steels.
This series of lectures is organised by Professor Fabio Miani of the University of Udine in Italy.
Associated teaching materials can be found on:
phase-trans.msm.cam.ac.uk/teaching.html
H. K. D. H. Bhadeshia