New icosahedral phases in Ti–transition-metal alloys

We report, for the first time, the formation of the icosahedral phase (i phase) in rapidly quenched ${\mathrm{Ti}}_2$Mn and ${\mathrm{Ti}}_2$Co alloys, and verify i-phase formation in ${\mathrm{Ti}}_2$Fe. Transmission electron microscopy (TEM) and x-ray diffraction measurements are presented. The i phase in ${\mathrm{Ti}}_2$Mn occurs at a stoichiometry for which there is no similar, crystalline, intermetallic phase. The ${\mathrm{Ti}}_2$Mn alloys show the strongest arcs of diffuse scattering in the TEM diffraction of any material to date and will enable quantitative checks of existing models for the first time. Distinct anisotropic peak shapes are observed in all diffraction orientations for this alloy.