TWO PROBLEMS IN LEDGEWISE GROWTH OF FERRITE REQUIRING FURTHER ADVANCED EXPERIMENTAL TECHNIQUES FOR THEIR SOLUTION

摘要

Two major problems that have arisen in studies of the ledgewise growth of ferrite are summarized. Difficult, long-standing questions about the origins and the lateral migration mechanisms of growth ledges may now be addressable with a new technique proposed here: TEM-based Computer Axial Tomography (TEM-CAT). Successful development of this technique would also aid significantly in attacking the second problem: the chemistry of kinks on the risers of growth ledges in Fe-C-X (and more complicated) alloys in which X induces a strong coupled-solute drag effect (C-SDE). A recent investigation in an Fe-C-Mo alloy demonstrated that the Mo detected at α:γ boundaries with the STEM technique, as well as the previously employed techniques of EELS (electron energy loss spectroscopy), 1DAP (one-dimensional field ion atom probe) and 3DAP (three-dimensional field ion microscope atom probe), was associated with segregation to these boundaries during transformation stasis, rather than with accumulation at kinks on growth ledge risers during growth as had long been anticipated. The possibility is raised that the combination of TEM-CAT with further refinement the 3DAP technique may permit the desired measurements to be made.