Icosahedral quasicrystals of Al-Cu-Li are formed by solid-state reaction at the grain boundaries of host alloy. Convergent-beam electron-diffraction measurements confirm that the symmetries of the quasicrystals belong to the $m\overline{3}\overline{5}$ point group. The icosahedral grains are formed by a nucleation and growth process and are strongly oriented at the grain-matrix interface. The stability of the icosahedral phase is compared with that of metallic glasses produced by a similar technique.

• Received 27 February 1986

DOI:https://doi.org/10.1103/PhysRevLett.56.2276