Point defect evolution in Ni, NiFe and NiCr alloys from atomistic simulations and irradiation experiments

Abstract

a b s t r a c tUsing molecular dynamics simulations, we elucidate irradiation-induced point defect evolution in fcc pure Ni, Ni 0.5 Fe 0.5 , and Ni 0.8 Cr 0.2 solid solution alloys. We find that irradiation-induced interstitials form dislocation loops that are of 1/3h1 1 1i{1 1 1}-type, consistent with our experimental results. While the loops are formed in all the three materials, the kinetics of formation is considerably slower in NiFe and NiCr than in pure Ni, indicating that defect migration barriers and extended defect formation energies could be higher in the alloys than pure Ni. As a result, while larger size clusters are formed in pure Ni, smaller and more clusters are observed in the alloys. Vacancy diffusion occurs at relatively higher temperatures than interstitials, and their clustering leads to the formation of stacking fault tetrahedra, consistent with our experiments. The results also show that the surviving Frenkel pairs are composition dependent and are largely Ni dominated.

A new approach for electronic heat conduction in molecular dynamics simulations

“…Now, we turn our attention to simulate far from equilibrium phenomenon such as ion irradiation, where electronic excitations and ionizations are significant. Irradiation in metallic systems has been studied in several works including only the effect of the phonons [31,32]. Here, we include the effect of the electrons and phonons using the proposed approach.…”

The effect of alloying nickel with iron on the supersonic ballistic stage of high energy displacement cascades

“…These alloys possess a simple face centered cubic structure (fcc), but are made of several principle elements (such as NiFeCoCrMn), in contrast with conventional alloys that typically contain only one principle component. This high chemical complexity was shown to reduce electronic [2,3] and phonon [4] mean free paths, as well as slow down defect mobility [5,6]. While these properties are known to be important for radiation damage evolution, the mechanisms that explain energy dissipation and defect production in these systems remain largely unexplored.…”

Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys

“…The complicated random arrangement of alloying elements and local chemical environment at atomic level lead SP-CSAs to exhibit extraordinary properties compared with traditional alloys, such as high thermal stability and hardness, high strength-to-weight ratio, high-temperature strength, great wear and fatigue resistance, and also excellent corrosion resistance13141516. In addition, the high-level site-to-site lattice distortions and compositional complexities in SP-CSAs can effectively reduce the mean free path of electrons, phonons and magnons; these distortions and complexities can also be used to modify formation energies, migration barriers and diffusion pathways of irradiation-induced defects, thereby modifying defect generation, interaction, interstitial–vacancy recombination in the early stages of irradiation17181920. A recently published paper indicates that equiatomic alloys may be more resistant to radiation damage than the corresponding pure elements21.…”