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Conventionally cast Fe-Al-C alloys are extremely brittle containing combinations of ferrite, carbide and other phases. Rapid solidification has the potential of altering the microstructure to subsequently change the resulting mechanical properties. An apparent conflict exist concerning the effect of rapid solidification on the resulting microstructure of these alloys. Inoue and co-workers, using transmission electron microscopy (TEM) and electron diffraction analyses, reported the presence of several non-equilibrium phases including austenite (fcc - γ) and ordered austenite (Ll2-γ') structures on alloys containing 1.7 to 2.1 C and 6 to 12 Al in weight % (w/o) on melt spun ribbons 30 μm in thickness. Han and Choo, using x-ray diffraction analysis on 30-48 μm thick melt spun ribbons concluded that this ordered fee phase is rather an austenitic phase in which phase decomposition accompanied by sideband phenomenon had occured.Single roller melt spinning technique was used to make ribbons 35-70 μm thick and 0.5-5 mm wide. X-ray diffration analysis showed single phase austenite for samples 2-6 w/o AI and 2 w/o C. Samples with 8-10 w/o AI and 2 w/o C also showed several superlattice lines in addition to the fundamental fcc peaks.

A formidable obstacle to develop the optimal conditions for growing dislocation-free crystals has been the lack of a direct technique to monitor the perfection of the solid/liquid (S/L) interface during growth.Recently we have developed a technique which detects, in-situ, the emergence of dislocation(s) at the crystallization front. This novel technique is based on the thermoelectric principles, and utilizes the dependence of the Seebeck emf generated across the S/L interface upon the interface temperature, crystal orientation, and dopant concentration.The technique was used to directly measure the S/L interface temperature during growth of Ga and In-doped Ga.For the latter, the technique also shows the breakdown (instability) of the faceted interface, which leads to the entrapment of the In-rich bands.