Effect of elastic interaction energy on coarsening of gamma ' precipitatesin a mechanically alloyed ODS Ni-base superalloy

The coarsening behavior of gamma' precipitates with a uniform size distribu tion and with a bimodal size distribution in a mechanically alloyed ODS Ni- base superalloy were investigated to clarify the effect of elastic interact ion energy on the coarsening behavior of gamma' precipitates. The coarsenin g rate decreased with increasing size of gamma' precipitates with a uniform size distribution, contrary to the classical LSW theory, and the coarsenin g behavior of gamma' precipitates with a bimodal size distribution exhibite d Ostwald ripening in which the larger precipitates grow at the expense of smaller precipitates. The driving force for coarsening of gamma' precipitat es was analyzed based on the two-particle model, considering the effect of elastic interaction energy in addition to the effect of interfacial energy. The contribution of elastic interaction energy on the total energy was fou nd to increase with increasing size of precipitates, and the decelerated co arsening of gamma' precipitates was attributed to the decrease in the drivi ng force for coarsening with increasing size of precipitates. (C) 1999 Kluw er Academic Publishers.