Solute effects on edge dislocation pinning in complex alpha-Fe alloys

Abstract

Reactor pressure vessel steels are well-known to harden and embrittle under neutron irradiation, mainly because of the formation of obstacles to the motion of dislocations, in particular, precipitates and clusters composed of Cu, Ni, Mn, Si and P. In this paper, we employ two complementary atomistic modelling techniques to study the heterogeneous precipitation and segregation of these elements and their effects on the edge dislocations in BCC iron. We use a special and highly computationally efficient Monte Carlo algorithm in a constrained semi-grand canonical ensemble to compute the equilibrium configurations for solute clusters around the dislocation core. Next, we use standard molecular dynamics to predict and analyze the effect of this segregation on the dislocation mobility. Consistently with expectations our results confirm that the required stress for dislocation unpinning from the precipitates formed on top of it is quite large. The identification of the precipitate resistance allows a quantitative treatment of atomistic results, enabling scale transition towards larger scale simulations, such as dislocation dynamics or phase field.

The Dominating Mechanisms for the Formation of Solute-Rich Clusters in Steels under Irradiation

“…These studies revealed that Cu, Mn, Ni, and P (Si has not been studied because of the absence of a suitable Fe-Si interatomic potential) naturally tend to accumulate around extended defects, such as dislocation loops and lines. They thus create energetically stable clouds around them, as well as precipitates (the simulations specifically suggest the formation of Cu and NiMn B2 phase precipitates, or Mn-rich regions, attached to dislocation loops and lines) [58,59]. Based on these considerations, we propose here the general scenario illustrated in Fig.…”

Atom probe characterisation of segregation driven Cu and Mn–Ni–Si co-precipitation in neutron irradiated T91 tempered-martensitic steel

“…As shown by J. Ke et al ( 2018) [29], RIS results in Ni and Si segregation, which is sufficient to drive precipitation. However, it should be noted that thermal segregation and precipitation, which is greatly accelerated by RED, could also be significant [88][89][90].…”

A multi-scale study of the interaction of Sn solutes with dislocations during static recovery in α-Fe

“…Solute atoms are considered to affect recovery via solute drag effect on dislocation motion [51]. The solute segregation around dislocation cores pins dislocations, making them sessile and a high driving pressure is then required for the dislocations to escape from the solute environment [52,53,54,55,56]. Takeuchi et al [57] and Nabarro [58] theoretically treated the solute drag effect on a climbing and a gliding dislocation.…”