Shape of precipitates in (Ni)under-bar-Al-Mo single crystals

A method is presented to determine the shape of the average precipitate fro m anisotropic small-angle scattering patterns from single crystalline alloy s during decomposition. The form factor squared of an average precipitate i s described by an analytical expression with a single parameter, the morpho logy parameter a, to account for changes from spherical to cuboidal shape. The method is applied to microstructural states of Ni-12 at.% Al-2 at.% Mo and Ni-10 at.% Al-5 at.% Mo after aging treatments of up to 10 h at 970 or 1070 K. The value of a increases with aging time and smaller Mo content, in good agreement with the average shape of precipitates obtained from transm ission electron microscopy.