A NEW EXAMPLE OF NONCRYSTALLINE MICROSTRUCTURE IN METALLURGY

We report on a non-crystalline microstructure encountered in particles that are formed during the annealing of some steels. The electron dif fraction patterns taken on small areas are those of a crystalline phas e but the diffraction patterns taken on larger area exhibit non-crysta lline symmetry. These anomalous diffraction patterns are interpreted a s the result of coherent diffraction between nanometer size domains. O bservations show that a crystalline phase identified as a X-phase stru cture is involved in this domain microstructure. Some of the electron diffraction pattern features suggest that an icosahedral phase might a lso be present. However investigations are under progress in order to check this point.