Orientational relationship between a B.C.C. phase and a new icosahedral phase in Ti-V-Si alloys

We report, for the first time, the formation of the icosahedral phase (i-phase) in rapidly quenched Ti_73-xV₂₇ Si_x alloys, where 13 ≤x ≤ 25. Transmission electron microscopy (TEM) lattice image studies show that the i-phase occurs with b.c.c. phase of large unit cell. Diffraction studies demonstrate that the two phases are coherently related; the cubic <001) directions are parallel to three of the two-fold icosahedral axes, the < 111) directions are parallel to the threefold icosahedral axes and the <530) cubic directions are nearly parallel to the fivefold directions. The b.c.c. lattice constant, a0= 12-98 A, is related to the quasilattice constant, 4-72 A, suggesting different projections from the same six-dimensional cubic lattice. These observations demonstrate the similarity of these two structures. A determination of the atom locations in this crystalline phase should provide information of the atomic positions in the icosahedral phase.