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

Abstract

The microstructures of Al65Cu20Cr15 as-cast and as-quenched master alloys and Al–Cu–Cr phases in Al65Cu20Cr15 particles/Al base composites after hot-pressing are investigated by transmission electron microscope and electron probe microanalyser. Two icosahedral quasicrystals SIQC and FIQC, two approximants to icosahedral quasicrystal IIA and FIA, one decagonal quasicrystal DQC, three approximants to decagonal quasicrystal DA1, DA2 and Θ, a new Al–Cu phase ξ that have a monoclinic structure with lattice parameter a=1.2 nm, b=0.9 nm, c=0.8 nm, β=130° and three τ type phases τ2, τ4 and τ7 were found. The composition–structure diagram in the Al–Cu–Cr system was drawn from phases above, in which there are two e/a-constant lines: one is the icosahedral quasicrystalline line with e/a=1.86; the other is the decagonal quasicrystalline line with e/a=2.09.