Grain size effects in the quasi-static fracture resistance of thermally embrittled RPV steel (annealed microstructures)

Abstract

The elastic-plastic fracture toughness and crack extension behavior under quasi-static loading regimes of the as-received and several thermally embrittled states of a reactor pressure vessel (RPV) steel were assessed on the basis of microstructural parameters. Through a simple rule of mixture that is typically applied for composite materials, it was found that the equivalent grain size (EGS) of dual-phase annealed microstructures is the controlling parameter of the fracture properties. It was concluded that a Hall-Petch type relationship correlates the J-fracture mechanics criteria to the EGS.