The structure of ternary compounds in a devitrified Al-rich Al-Ni-Gd alloy

A high-resolution transmission electron microscopy study has been performed on the phases present in an Al-8 at.% Ni-7 at.% Gd alloy produced from amorphous gas-atomized powder precursors by hot compaction and extrusion. The alloy had a fine fully devitrified microstructure consisting of: α-Al, binary Al3Gd, and two ternary phases; a rod-like τ1 phase and a plate-like τm/τμ phase. Upon annealing the former coarsened whereas the latter was eliminated. It is shown that these phases exhibit the Al19Ni5Gd3 and Al23Ni6Gd4 crystal structures, respectively, and not those reported elsewhere for the τ1 and τm/τμ phases.