THE EFFECT OF IRRADIATION-INDUCED MATRIX BARRIER HARDENING ON IRRADIATION-ASSISTED STRESS CORROSION CRACKING (IASCC) IN AUSTENITIC STEELS AND NICKEL BASED ALLOYS

摘要

Mechanistic models for inter-granular (IG)fracture are reviewed. The favoured approach considers apropagating IG crack with plastic deformation occurringat the crack tip. The key parameter in controlling the easeof crack propagation is the work of fracture, which islinked to the fracture toughness. It will be shown that thework of fracture can be estimated through a series ofequations that consider: 1) surface energy; 2) workhardening exponent; 3) grain boundary (GB) energy; 4)GB segregation of embrittling elements; and 5) GBstructure. In particular, the effects of barrier hardeningon the GB energy (item 3)) will be reviewed. Newequations describing the influence of irradiation-induced:1) dislocation loop damage; 2) precipitation; on the GBenergy, will be discussed. The relation of fracturetoughness predicted by the model to IASCC growth ratesand initiation times will be assessed. Applications of thenew model to IASCC in austenitic steels and nickel basedalloys will be described.