Atomic Simulations for Packing Changes of Nano-Sized Cu Clusters Embedded in the Febulk on Heating

Peng Yu,Linxiu Du,Lin Zhang

doi:10.3390/met11060934

Abstract

Understanding of the defect evolution mechanism under irradiation is very important for the research of pressure vessel steel embrittlement. In this paper, the embedded atom method (EAM) based canonical ensemble molecular dynamics (MD) method was used to study the evolution of the stacking structure of different nano-sized Cun (n = 13, 43 and 87) clusters in an Febulk embedded with BCC lattice structure during continuous heating. The mean square displacement, pair distribution functions and atomic structures of Cu atom clusters at the nanometer scale were calculated at different temperatures. The structural changes present apparent differences, for the Febulks contain nano-sized Cu clusters with different atom numbers during heating. For the Febulk–Cu13 system, since the ability to accommodate the atomic Cu in the Fe substrate is lesser, a small number of Cu atoms in BCC lattice positions cannot influence the whole structure of the Fe-Cu system. For the Febulk–Cu43 system, with an increase in temperature, a Cu atomic pile structural change happened, and the strain areas decreased significantly in the Febulk, but a single strain area grew large. For the Febulk–Cu87 system, when the Cu atoms are constrained by the Fe atoms in bulk, only a few of the Cu atoms adjust their positions. With the increase in temperature, strain in the Fe eased.

Highlights

Metals 2021, 11, 934. https://Nuclear power is of great strategic significance for pollution reduction and energy demand relief because of its many advantages including environmental protection, economic competitiveness and technological independence [1,2,3,4,5]
Because the reactor pressure vessel (RPV) operates under high temperature, high pressure and neutron irradiation for a long time, its integrity is crucial to the safety and life of the nuclear reactor and the entire nuclear power plant
A large number of studies have shown that after long-term neutron irradiation at 288 ◦ C, the impurity element Cu in the RPV steel will be precipitated as a Cu-rich nanometer phase, which is the main reason for the increase in tough–brittle transition temperature of RPV steel [9,10,11,12,13,14,15,16]

Summary

Introduction

Nuclear power is of great strategic significance for pollution reduction and energy demand relief because of its many advantages including environmental protection, economic competitiveness and technological independence [1,2,3,4,5]. A large number of studies have shown that the precipitation of the Cu-rich nano-phases is one of the main causes for irradiation embrittlement of the RPV steels [17,18,19,20,21,22,23,24,25,26,27]. Cai et al [28] studied nano-scale Cu-rich precipitates in reactor pressure vessel (RPV) model steel after water quenching, tempering and thermal aging at 400 ◦ C. Canonical ensemble (NVT) molecular dynamics (MD) simulations within the frame of the embedded atom method (EAM) were used to study the evolution of the packing structure of nano-sized Cu clusters embedded in the Febulk with a BCC lattice structure during aging treatment at different temperatures. Cu clusters constrained by the matrix at the atomic scale during the heating process are studied in order to study the influence of the atomic stacking structure in Cu clusters at different temperatures on the matrix structure, which can provide an understanding of the behavior of these small size precipitated clusters during thermal aging

Model and Simulation

FCC boundary

Three-dimensional projection ofbulk the–Cu

Results and Discussion

Mean square displacements of atoms

Conclusions