On the constitution of the high-Al region of the Al-Cr alloy system

Abstract

The compositional range of the Al-Cr alloy system above 75 at.% Al was investigated by powder X-ray diffractometry, differential thermal analysis, scanning and transmission electron microscopy. A hexagonal phase isostructural to mu-Al4Mn (a approximate to 2.00 nm, c approximate to 2.47 nm) was found to be formed in a compositional range from about 78.7 to 81.3 at.% Al. A higher-AlAl11Cr2 phase was associated with the C-centered monoclinic (pseudo-orthorhombic) structure with a approximate to 1.76 nm, b approximate to 3.05 nm, c approximate to 1.76 nm and beta approximate to 90 degrees reported earlier. No orthorhombic structure with a approximate to 3.46 nm, b approximate to 2.00 nm, c approximate to 1.24 nm related in the literature to either Al45Cr7, Al11Cr2 or Al4Cr was revealed at all. The peritectic temperature of the Al11Cr2 phase formation was found to be similar to 865 degrees C and the stability of this phase was confirmed down to 600 degrees C. (c) 2007 Elsevier B.V. All rights reserved