Publication Details

Dippenaar, R. J. & Phelan, D. J. (2002). Delta-Ferrite Recovery Structures in Low Carbon Steels. In R. Aune & S. Sridhar (Eds.), Proceedings of the Mills Symposium (pp. 283-292). UK: National Physical Laboratory (NPL).


The development of delta-ferrite recovery sub-structures in low carbon steels has been observed in-situ utlhsing laser scanniJlg confocal microscopy (LSCM). Well developed subboundaries with interfaCial' energies much smaller than that of delta-fen'ite grain boundaries fOfmed following transformation from austenite to delta-fen'ite on heating. Transfonnatioll stresses associated with the austenite to delta-fenite phase transt'onnation generate dislocations that subsequently recover into sub-boundaries by a process of polygonisation. Experimental evidence in suppol1 of this proposal was found in a ferritic stainless steel. Thermal cycling through the high temperature delta-ferrite/austenite/delta-fel1'ite phase b'ansformation leads to the development of a strong recovery substructure, wh.ich in turn. modifies the low temperature austenite decomposition product from WidmansUilten/bainite to polygonal fen'ite, with a commensurate chauge in hardness.

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