THE DIFFUSE OMEGA STRUCTURE - ITS RELATIONSHIP TO SPONTANEOUS VITRIFICATION IN BETA-TI-CR

Diffuse scattering from quenched beta-Ti-Cr alloys is investigated usi ng electron diffraction. A new structural model based on displacive at omic shifts coupled to chemical short-range order is described and sho wn to account for the observed diffuse scattering. Changes of the diff use scattering in Ti0.6Cr0.4 due to 1 MeV electron irradiation support the presence of chemical short-range order in quenched Ti-Cr. The sig nificance of these results in light of recent reports that the quenche d-in beta phase in a concentrated Ti-Cr alloy undergoes a transformati on to the amorphous state during low temperature annealing, a process known as spontaneous vitrification, is discussed.