Software for simulating radiation damage was created to examine the mechanics of defect formation in polycrystalline materials.

A set of software known as object-kinetic Monte Carlo-lattice-kinetic Monte Carlo (OKMC-LKMC) hybridization simulation software was recently developed by the research group led by Prof. Liu Changsong from the Institute of Solid State Physics (ISSP), Hefei Institutes of Physical Science (HFIPS), and Chinese Academy of Sciences (CAS). This software allows for simulating the progression of displacement damage in polycrystalline metals across time and space scales.

The research team investigated the development and accumulation of vacancies at iron (Fe) grain boundaries (GBs) with this software.

The findings were presented and discussed in the Journal of Nuclear Materials.

It was discovered that PC/NC (polycrystalline/nanocrystalline) Fe has enhanced radiation resistance. In past multiscale reproductions, GBs were often preoccupied as two-layered planes without explicit designs, and a progression of enthusiastic and motor boundaries was utilized to describe the primary qualities of GBs.

However, GBs have distinct local structures and defects due to their diversity of character. A lot of defect-related atomic information would be missed if these properties were simply abstracted as a single interaction parameter, affecting the precise prediction of defect evolution over a long time scale.

This study’s technology not only distinguishes the spatial position dependence of defect properties at GBs but also coarsely simulates the evolution of defects beyond the GB region.

Several LKMC-simulated V motion trajectories are in close proximity to the GBs. The GB’s location is denoted by the horizontal line. Credit: Li Xiaolin

Scientists researched the amassing components of Versus at Fe GBs, principally centered around the connection cycles of Versus with various GBs.

The relationship between the GB character and V accumulation was made clear by the findings. In addition to the well-known GB trapping of the V, the atomic processes of V emission and leakage were discovered at high temperatures. The event of these cycles relies on the GB character. In light of the mix of grain size, V development energy at the GB, and relocation energy hindrance inside the GB, the coupling condition of grain size with GB character was proposed.

When this equation is satisfied, the defect cruise along the GB stops the defect emission process that started in the high energy level region. In the case of a small grain size, this creates uncertainty regarding the relationship between radiation performance and defect-GB binding strength.

New V-GB interaction processes and their coupling are revealed by this research. As a mechanism reference for experimentally optimizing the radiation resistance of materials based on GB engineering, these findings have general relevance for other PC systems and can shed light on the radiation response of PC materials.

More information: Xiaolin Li et al, Vacancy accumulation mechanism at iron grain boundaries: The influence of grain boundary character and its coupling with grain size, Journal of Nuclear Materials (2023). DOI: 10.1016/j.jnucmat.2023.154386

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