Crystallographic relationships of the

In a transmission electron microscopic study of rapidly as well as slowly solidified alloys in the composition range Al7Cr-Al4Cr, three mutually related structural variants of Al4Cr, in ad- dition to the well-known monoclinic Ф-Al45Cr7, were found. The hexagonal μ-Al4Cr is iso- structural with μ-Al4Mn (P63/mmc), with aμ = 2.00 nm and cμ = 2.47 nm. The two orthorhombic e- and e′-Al4Cr phases, one being B-centered and the other primitive, havea ≈ √3aμ = 3.46 nm,b ≈ aμ = 2.00 nm, andc ≈ cμ/2 = 1.24 nm. These three Al4Cr phases are not only themselves structurally connected, but are also closely related both to the Al-Cr icosahedral quasicrystal found earlier and to the Al-Cr decagonal quasicrystal found for the first time in the present investigation in rapidly solidified Al-Cr alloys with 18 to 22 at. pct Cr.