1995 Volume 35 Issue 12 Pages 1502-1508
The growth behavior of cellular δ phase in Ni-base alloy, modified Inconel X-750 type alloy (X-750M), was investigated mainly using optical and transmission electron microscopy.
The values of n in the Johnson-Mehl equation for the growth of the cellular δ phase in X-750M which was aged in various conditions after a solution heat treatment were estimated to be 1.69-1.84.
The values of n in the case of X-750M which was pre-aged at 943 K for 253 ks after a solution heat treatment followed by aging in various conditions were estimated to be 1.44-1.67. The obrtained value of n suggested that the growth of the cellular δ phase in X-750M after the pre-aging treatment obeyed a volume diffusion rate control with zero nucleation rate. Transformation curves of γ+γ'' phases to the cellular δ+γ phases in the specimens aged after the pre-aging treatment were consistent with a theoretical one. The apparent activation energy for the growth of the cellular δ phase in X-750M aged after the pre-aging treatment was estimated to be 232 kJ/mol, which is nearly equal to that for diffusion of solute atoms in the alloy.