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

Abstract

The mechanistic modeling of irradiation induced embrittlement of reactor pressure vessel steels strongly depends on the precise evaluation of flow stress behavior. This requires accurate characterization of change in both the yield strength as well as the strain-hardening capacity. A dislocation-density based crystal plasticity model is thus developed in this work to quantify these variations with irradiation. The model considers the interaction between dislocations and irradiation induced defects such as self-interstitial atomic loops, vacancy clusters and precipitates to obtain flow stress variations in irradiated ferritic alloys. The model is calibrated and validated for polycrystalline pure-iron and iron-copper alloys, neutron-irradiated to different dose levels under typical pressure vessel operating conditions. A comparison with experimental results show that the model is able to quantify the changes in flow stress behavior accurately. At 0.2 dpa a loss of strain-hardening capacity beyond 2% strain is also obtained from the model. The yield strength increase with irradiation obtained from the model is also compared with analytical strengthening models based on Orowan's equation.

Crystal plasticity-based creep model for solution-strengthened nickel-based alloys

“…Thus, only the glide parameters can be calibrated from this experimental data. For the calibration, a microstructure of size 200 × 200 × 200 μm 3 with 64 cubic grains is considered similar to Chakraborty and Biner (2016). Random Euler angles are assigned to each grain and the pole figure of [0 0 1] axis along the loading direction is shown in Figure 1(a).…”

Crystal plasticity-based creep model for solution-strengthened nickel-based alloys

“…The microstructure is discretised with 64 hexahedral elements, where, one element is associated with every grain. The discretisation strategy is relatively accurate to obtain average plastic properties of strain hardening material (Chakraborty and Biner, 2016), as is the case here. The distribution of Euler angle, , for the synthetic microstructure utilised in this work is shown in Figure 1(b).…”

“…However, a vast majority of the literature on CP is directed towards understanding elasto-viscoplastic behaviour and texture development in metallic alloys (Roters et al, 2010). In the last few decades CP-based finite element method (CPFEM) has been widely used not only to obtain equivalent macroscopic responses of representative volume elements (RVEs) (Chakraborty and Biner, 2016) but also discern damage localisation that may lead to eventual failure (Ghosh and Chakraborty, 2013). However, CP-based models of vacancy mediated creep is limited and has been ventured into recently by few authors.…”

“…In the present work, the climb model proposed in Geers et al (2014) has been modified and is appended to the dislocation density-based glide model described in (Chakraborty and Biner, 2016) to model creep in single crystals of solution strengthened nickel-based alloys. The glide-climb model is elaborated in the next section.…”

Application of roller burnishing technologies to improve the wear resistance of submerged pump parts made of powder alloys

“…Figure 3 shows the characteristic type of surface defects of the submersible pump guide vanes formed during the casting into sand molds. It should be emphasized that for the sake of clarity, the figure especially presents an obvious defect; such guide vanes will not be allowed into operation [26]. However, even a small number of pores formed in the surface layer of the part during casting can lead to premature loss of operability.…”