AN ELECTRON-DIFFRACTION INVESTIGATION OF THE DIFFUSE OMEGA-STRUCTURE IN QUENCHED TI-3D TRANSITION-METAL ALLOYS

Diffuse scattering resembling diffraction from the omega phase is inve stigated in quenched b.c.c. (beta) Ti-Cr using electron diffraction. A new structural model is presented which can reproduce the large shift s of diffuse peaks from the positions of omega-phase Bragg reflections which are seen in this system. Using the model it is proposed that CS RO in conjunction with an atomic size difference are responsible for t he occurrence of this structure in quenched beta Ti-3d metal alloys. E vidence is presented for an electronic origin for CSRO in these system s.