ICOSAHEDRAL AND RELATED PHASE-FORMATION IN RAPIDLY QUENCHED TI-ZR-FE ALLOYS

We report the formation of the icosahderal phase (i-phase) in some rapidly quenched TixZryFez (45 less than or equal to x less than or equal to 70; 5 less than or equal to y less than or equal to 25; 20 less than or equal to z less than or equal to 30) alloys. Transmission electron microscopy (TEM) studies show that unlike the Ti-Zr-Ni i-phase, i(TiZrFe) is strongly disordered, showing strong spot anisotropy and intense localized diffuse scattering. These features, and a smaller quasilattice constant for i(TiZrFe) (a(0)=4.85 Angstrom) than for i(TiZrNi) (a(0) = 5.12), indicate that i(TiZrFe) is more closely related to the icosahedral phases found in Ti-Sd transition metal-Si alloys. TEM studies also reveal many related crystalline phases dominated by local polytetrahedral order, including alpha(TiZrFe), a bcc phase that is a 1/1 approximant to the i-phase, the lambda-phase, an orthorhombic phase that appears to be an approximant to a decagonal phase, a Laves phase of the hexagonal MgZn2-type, and a Ti2Ni-type fee phase. Evidence for ordering in the alpha(TiZrFe) and bcc solid solution phases is presented.