Local segregation versus irradiation effects in high-entropy alloys: Steady-state conditions in a driven system

Abstract

We study order transitions and defect formation in a model high-entropy alloy (CuNiCoFe) under ion irradiation by means of molecular dynamics simulations. Using a hybrid Monte-Carlo/molecular dynamics scheme a model alloy is generated which is thermodynamically stabilized by configurational entropy at elevated temperatures, but partly decomposes at lower temperatures by copper precipation. Both the high-entropy and the multiphase sample are then subjected to simulated particle irradiation. The damage accumulation is analyzed and compared to an elemental Ni reference system. The results reveal that the high-entropy alloy-independent of the initial configuration-installs a certain fraction of short-range order even under particle irradiation. Moreover, the results provide evidence that defect accumulation is reduced in the high-entropy alloy. This is because the reduced mobility of point defects leads to a steady state of defect creation and annihilation. The lattice defects generated by irradiation are shown to act as sinks for Cu segregation.

Chemical short-range order in derivative Cr–Ta–Ti–V–W high entropy alloys from the first-principles thermodynamic study

“…These results reveal that the short-range order maintains even under irradiation and the thermodynamically stabilised HEAs predicted in this study represent a steady-state configuration in a driven system. 98 To correlate the experimental observation of Cr/V segregation with the properties of irradiation-created defects, a rate theory model in which the defect mobilities and their recombination probability should be taken into consideration, is currently developing to investigate the steady-state conditions of the long-term microstructural evolution of the HEAs under irradiation. A further systematic investigation of point defect (vacancy and interstitial) properties would be very desirable for understanding the micro-structural evolution and the origin of exceptional radiation resistance in W-based HEAs.…”

“…43 A recent computational study on relationship between the SRO-induced local segregation and radiation effects in CoCuFeNi HEAs has been reported. 98 By using hybrid molecular dynamic and Monte-Carlo simulations, the study in question showed that the mobility of point defects created by irradiation can be changed and the system reaches a steady-state configuration of defect creation and annihilation with a tendency of copper segregation. For understanding of origin of the exceptional radiation resistance of the W-based HEAs under irradiation, a deeper investigation of kinetic properties of point defect migration and diffusion is crucial for clarifying additional mechanism for Cr and V segregation.…”

Origin of radiation resistance in multi-principal element alloys

“…Therefore, various atomistic simulation techniques have been conducted to estimate the residual defects evolution. For example, the evolution of residual defects was analyzed using hybrid MC/MD simulations through a multiple cascade 25 and a kinetic Monte-Carlo (KMC) or MD simulation on a sample with point defects 15 , 26 . In this study, we chose the defect evolution simulation method which performs the MD simulation at a specific temperature on a sample containing randomly-distributed point defects in order to most efficiently analyze the interaction among residual defects given as point defects at a specific temperature.…”

Microscopic structure of a heavily irradiated material

“…Can the high-dose limit be explored by a direct atomistic simulation? Studies involving applications of molecular dynamics to modeling high entropy alloys, exposed to a relatively high irradiation dose, were carried out by Koch et al [53] and Granberg et al [30]. The simulations, involving random initiations of many hundreds of cascade events in the same simulation cell, have enabled reaching the level of exposure close to φ ∼ 0.7.…”