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 Ti_x, Zr_y, Fe_z, (45 ≤ × ≤ 70; 5 ≤ y ≤ 25; 20 ≤ z ≤ 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) (a₀ = 4.85Å) than for i(TiZrNi) (a₀ = 5.12), indicate that i(TiZrFe) is more closely related to the icosahedral phases found in Ti-3d transition metal-Si alloys. TEM studies also reveal many related crystalline phases dominated by local polytetrahedral order, including α(TiZrFe), a bcc phase that is a 1/1 approximant to the i-phase, the λ-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 fcc phase. Evidence for ordering in the α(TiZrFe) and bcc solid solution phases is presented.