An investigation on the coarsening behavior of γ′ precipitate in GTD-111 Ni-base superalloy

Morphology of gamma' precipitates affects mechanical properties of Ni-base superalloys. In this research study, the coarsening behavior of gamma' precipitates in Ni-base superalloy GTD-111 was investigated. The alloy was solution-treated at 1200 degrees C for 4 h and water quenched to obtain single size distribution of the precipitates. Aging at 1000 degrees C up to 200 h was carried out to examine the effect of aging time on the growth of gamma' precipitates. The shape of gamma' precipitates changed from sphere to oval and then to cube as the aging time was increased. Moreover, the coarsening of gamma' precipitates started fast initially, whereas it slowed down as the growth continued, contrary to the Lifshitz-Slyozov-Wagner theory. The decelerated coarsening of gamma' precipitates was attributed to the effect of elastic interaction energy and decrease in driving force. Finally, the activation energy for diffusion of solute atoms or the growth of gamma' precipitates in GTD-111 alloy was calculated.