Parametric study of irradiation effects on the ductile damage and flow stress behavior in ferritic-martensitic steels

Abstract

a b s t r a c tFerritic-martensitic steels are currently being considered as structural materials in fusion and Gen-IV nuclear reactors. These materials are expected to experience high dose radiation, which can increase their ductile to brittle transition temperature and susceptibility to failure during operation. Hence, to estimate the safe operational life of the reactors, precise evaluation of the ductile to brittle transition temperatures of ferritic-martensitic steels is necessary. Owing to the scarcity of irradiated samples, particularly at high dose levels, micro-mechanistic models are being employed to predict the shifts in the ductile to brittle transition temperatures. These models consider the ductile damage evolution, in the form of nucleation, growth and coalescence of voids; and the brittle fracture, in the form of probabilistic cleavage initiation, to estimate the influence of irradiation on the ductile to brittle transition temperature. However, the assessment of irradiation dependent material parameters is challenging and influences the accuracy of these models. In the present study, the effects of irradiation on the overall flow stress and ductile damage behavior of two ferritic-martensitic steels is parametrically investigated. The results indicate that the ductile damage model parameters are mostly insensitive to irradiation levels at higher dose levels though the resulting flow stress behavior varies significantly.

Grizzly and BlackBear: Structural Component Aging Simulation Codes

“…A major part of the Grizzly development effort has focused on developing models to predict the underlying microstructure evolution leading to RPV steel embrittlement, with the goal of developing predictive models for embrittlement over longer-term exposure to the reactor environment. This has involved the development of models at the atomistic scale 11,12 to understand mechanisms of radiation damage to the crystal structure within grains, mean-field cluster dynamics models of precipitation, 13 crystal plasticity models to understand the effects of irradiation on flow stress behavior, 14,15 and cohesive zone model development to model temperature-dependent toughness. 16 Some of these microstructure evolution models are based on continuum theories, while many of them, particularly those that represent behavior at the atomistic scale, are not.…”

Crystal plasticity modeling of irradiation effects on flow stress in pure-iron and iron-copper alloys

“…Though, the dislocation-SIA loop interaction laws are unmodified from [25] (Eqs. 12,14), a more detailed dislocation evolution model is used in this work as compared to [25]. Hence, at first, the workability of the model is compared with the DD simulations.…”

“…In [11], temperature dependent cohesive zone model and flow stress parameters were utilized to obtain DBTT in RPV steels. In a parametric study using tensile test data for ferritic-martensitic steels [12], it has been shown that the variation of ductile damage parameters saturate with increasing irradiation dose levels, whereas the flow stress parameters still evolve. From these numerical studies it can be concluded that precise evaluation of flow stress variation with temperature and irradiation dose levels is essential to characterize DBTT shifts accurately.…”