A method of improving the mechanical properties of a .gamma./.gamma.'-.alpha. eutectic nickel-base superalloy body containing a .gamma.-phase, a .gamma.'-phase, and an aligned molybdenum fiber .alpha.-phase which comprises the steps (a) heating the body to a temperature at which at least a portion of the .gamma.'-phase will transform to a .gamma.-phase, (b) maintaining the heated body at said temperature to allow transformation of at least a portion of said .gamma.'-phase to a .gamma.-phase, and (c) cooling the transformed body to a temperature at which at least a portion of the .gamma.-phase precipitates as a modified .gamma.'-phase.