Abstract
A rapidly quenched Fe-Ti alloy has been investigated in relation to the stability of the icosahedral phase arising from the substitution of Fe by Si. For less than 6 at.% Si, a crystalline (f.c.c. of FeTi2) phase has invariably been found to be present. However, an X-ray diffraction study of the Fe-Ti-Si system clearly reveals that 6 at.% Si results in the formation of single-phase icosahedral quasicrystal. The changes in grain size and morphology resulting from Si substitution are reported. Electron diffraction studies of this alloy show arcs of diffuse intensity which are indicative of the structural disorder present in the quasicrytalline phase. Detailed investigations of the diffuse scattering in Fe-Ti-Si alloy are presented and the results are compared with those for other known alloy systems.