Intergranular cavitation in creeping alloys

Fracture at high temperature in structural alloys can be of several forms. Of these, the only one of interest here is the intergranular form of fracture that occurs under usual service stresses and takes a relatively long time to develop. This fracture goes through several stages, starting with nucleation of cavities along grain boundaries, followed by their growth by coupled diffusional flow and creep flow under conditions of gradual load shedding, leading to the development of quasi-homogeneously accumulated grain boundary facet cracks, without or with eventual macro-crack evolution before final fracture. The subject has seen active development during the past decade which, however, has not always led to a general consensus on the nature of the specific processes and their representation. The mechanistic details of intergranular fracture in creeping alloys have recently been critically assessed by Argon. Here the authors are interested in the mechanisms of cavity nucleation and growth