The relationship between activation energy and precipitate size for precipitate agglomeration

Superalloys are used in aggressive atmospheres in aero-engines and land-base gas turbines. IN738LC is an important superalloy used in gas turbines. Strengthening Ni3(Al,Ti,Nb) type precipitate phase in this superalloy goes through size and morphological changes with time and temperature. Experimental observations suggest precipitate motion as a whole in the matrix leading to agglomeration of nearby precipitates for coarsening, which is in contrast to the traditional Ostwald ripening. Likewise, contrary to the conventionally accepted view of constant activation energy, experimental data in this study indicate varying activation energy, which causes coalescence and relates to the precipitate size in the form of an increasing polynomial.