consequences on diffusion properties wwwmsmcamacuk phasetrans The Pearlite Reaction 1 µm upper bainite Sheaf is a rough object plastic zone hydrogen f ragmentation of martensite ID: 581358
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Percolation of phases in interface dominated structures:consequences on diffusion, properties
www.msm.cam.ac.uk
/phase-transSlide2
The Pearlite ReactionSlide3Slide4
1 µm
upper bainiteSlide5Slide6
Sheaf is a rough objectSlide7Slide8
plastic zone hydrogenSlide9Slide10
fragmentation of martensiteSlide11
Greasy austenitemartensite is brittleyet, dual phase steels etc are notexplained by austenite films thatlubricate deformation Slide12
greasy austenite?Slide13
200 Å
g
g
a
a
a
Caballero, Mateo, BhadeshiaSlide14Slide15
Caballero, Mateo, BhadeshiaSlide16
Caballero, Mateo, BhadeshiaSlide17Slide18Slide19Slide20
Sherif, 2005, Ph.D. thesis, CambridgeSlide21
Above percolation threshold
Below percolation thresholdSlide22
Geometrical percolation threshold of overlapping ellipsoidsSlide23Slide24
Hydrogen probingof austenite percolationSlide25
Hydrogen dissolves in ferrite, austeniteOkamoto:2004Slide26
hydrogen diffuses faster in ferrite, but there are complicationsCoe, 1973Slide27
Hydrogen embrittles iron both single and polycrystalline formsPfeil 1926normalpickledW. H. Johnson: ‘On some remarkable changes produced in iron and steel by the action of hydrogen and acids’, Proceedings of the Royal Society of London, 1875, 23, 168–179.Slide28
It is diffusible hydrogen that embrittlesit is atomic hydrogen that embrittlessubmerging H-containing steel causes frothingstronger steel more susceptibleW. H. Johnson: ‘On some remarkable changes produced in iron and steel by the action of hydrogen and acids’, Proceedings of the Royal Society of London, 1875, 23, 168–179.Slide29
Hobson, 1951Slide30
Tendency to embrittle scales with strengthHobson & Sykes, 1951or does it in fact scale with ductility in the absence of hydrogen?Slide31
Frohmberg, 1954Slide32
Fielding, Song, Bhadeshia, Suh, unpublishedSlide33Slide34
Fielding, Song, Han, Bhadeshia, Suh, Proc. Roy. Soc. A, 2014Slide35
Why is Gibbs energy free?Slide36
John SpeerWhich medal? Helmholtz or GibbsHelmholtz is at constant volumeGibbs at constant pressureSlide37Slide38Slide39