The microstructure analysis of Al-Cu-Cr phases in Al65Cu20Cr15 quasicrystalline particles Al base composites

The microstructures of Al65Cu20Cr15 as-cast and as-quenched master alloys a nd Al-Cu-Cr phases in Al65Cu20Cr15 particles/Al base composites after hot-p ressing are investigated by transmission electron microscope and electron p robe microanalyser. Two icosahedral quasicrystals SIQC and FIQC, two approx imants to icosahedral quasicrystal IIA and FIA, one decagonal quasicrystal DQC, three approximants to decagonal quasicrystal DA1, DA2 and Theta, a new Al-Cu phase xi that have a monoclinic structure with lattice parameter a=1 .2 nm, b=0.9 nm, c=0.8 nm, beta=130" and three tau type phases tau(2), tau( 4), and tau(7), were found. The composition-structure diagram in the Al-Cu- Cr system was drawn from phases above, in which there are two ela-constant lines: one is the icosahedral quasicrystalline line with e/a=1.86; the othe r is the decagonal quasicrystalline line with e/a=2.09. (C) 1999 Elsevier S cience B.V. All rights reserved.