Abstract
	Paper describes the effect of different heat treatment conditions on microstructures and mechanical properties such as hardness and tensile strength in wrought nickel base superalloy, X750. The aging temperatures were to affect the morphology of ??-precipitated particles relating to mechanical properties. The change in heat-treated microstructures were investigated and analyzed by utilizing optical microscopy (OM) and transmission electron microscopy (TEM). After various aging temperatures, the change in grain size could not obviously be found. However, after the solutioning, the volume fraction of gamma prime particles significantly decreases. The different aging temperatures resulted in the different size of the re-precipitated gamma prime particles. The size of precipitated particles increase with the higher aging temperature. The mechanical property results show that the aging temperature in the range of 700?C provided the maximum tensile strength and maximum hardness. It was found that the higher temperature of aging resulted in a decrease of all mechanical properties with an increase of ?? precipitate particles size. Therefore, from this work, it might be noted according to the previous theories that the mechanism of dislocation movements should be still shearing ?? particles until the size of ?? particles is about 12 nm after aging at 700?C for 20 hours, which is the standard aging condition and provides the maximum mechanical properties. For the larger ?? particle size after aging at higher temperatures, the dislocation bypass mechanism to avoid the ?? particles should be more pronounced resulting in the decrease of all mechanical properties.