THE GROWTH OF CELLULAR DELTA-PHASE IN 69N I-15CR-8FE-6NB BASE ALLOY

The growth behavior of cellular delta phase in Ni-base alloy, modified Inconel X-750 type alloy (X-750M), was investigated mainly by optical and transmission electron microscopy. The values of n in Johnson-Mehl 's equation for the growth of the cellular delta phase in X-750M aged in various conditions after a solution heat treatment were estimated t o be 1.69-1.84. The values of n in the case of pre-aged X-750M at 943K for 253ks after a solution heat treatment followed by aging in variou s conditions, were estimated to be 1.44-1.67. The obtained value of n suggested that the growth of the cellular delta phase in X-750M after the pre-aging treatment obeyed a volume diffusion rate control with ze ro nucleation rate. Transformation curves of gamma + gamma phases to t he cellular delta + gamma phases in the specimens aged after the pre-a ging treatment were consistent with a theoretical one. The apparent ac tivation energy for the growth of the cellular delta phase in X-750M a ged after the pre-aging treatment was estimated to be 232kJ/mol, which is nearly equal to those for diffusion of solute atoms in the alloy.