An Al-Cu-Ru partial phase diagram involving the icosahedral quasicrystal has been constructed along an Al-62-CU38-xRux = (x = 2.5-25 at%) isopleth. The icosahedral quasicrystal forms at 1020degreesC via a peritectic reaction between a liquid and Al68Cu12Ru20 phase and coexists with a liquid phase at temperature below the peritectic reaction. The icosahedral quasicrystal solidifies as a primary phase in the temperature range of 800-1020degreesC from the alloys in the composition range of 60-67.5 at% Al, 29.5-37.5 at% Cu, and 2.5-4 at% Ru. On the basis of the phase diagram, single grains of the Al-Cu-Ru icosahedral quasicrystal with a maximum size of 5 mm were successfully grown from Al-CuRu melts. (C) 2002 Elsevier Science B.V. All rights reserved.