Coarsening behavior of γ′ precipitates in the γ′ plus γ area of a Ni3Al-based alloy

The morphological evolution and coarsening kinetics of gamma' precipitates in the gamma'+gamma area of a Ni3Al-based alloy during isothermal aging at temperature range of 800 degrees C to 1000 degrees C have been investigated. For the aging temperature above 900 degrees C, the average size of gamma' precipitates increases and the morphology of gamma' precipitates gradually changes from cuboidal to strip-like and L-shaped with increasing aging time up to 50 h. The temporal evolution of the average size of gamma' precipitates is evaluated by the experimentally measured data and it suggests that the cube rate law fits better for experimental data at the early stage coarsening, while the square rate law fits better for the later stage coarsening. Moreover, using these determined values of coarsening rate constants which determined by using a coarsening rate equation based on the LSEM model, the activation energy of the early stage and later stage coarsening have been calculated as 174.2 kJ/mol and 186.3 kJ/mol, respectively. (C) 2018 Elsevier B.V. All rights reserved.