An intermediate phase appearing in L1(2)-Al3Zr to DO23-Al3Zr phase transformation of rapidly solidified Al-Zr alloys

Al100-xZrx (x = 5, 10, 15 at%) alloys were rapidly solidified into ribbons with a thickness ranging from 20 to 30 mu m by a single roller method. The rapidly solidified Al-Zr alloys are composed of alpha-Al and L1(2)-Al3Zr phases. When annealing in a temperature range of 573 to 773 K, a new phase was found to form in the Al100-xZrx (x = 5, 10, 15 at%) alloys. On basis of X-ray diffraction data and selected area diffraction patterns of transmission electron microscopy, the phase was determined to have a tetragonal structure with lattice parameters a = 0.3896 nm, c = 0.9006 nm for the Al95Zr5 alloy, a = 0.3895 nm, c = 0.9030 nm for Al90Zr10 and a = 0.3903 nm c = 0.9028 nm for Al85Zr15. When the annealing temperature is higher than 773 K, the tetragonal phase disappears and changes into the equilibrium DO23-Al3Zr phase.