Molecular dynamics simulation of dynamic migration of <inline-formula><tex-math id="M3">\begin{document}$\boldsymbol {\langle 100\rangle} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M3.png"/></alternatives></inline-formula> interstitial dislocation loops under (010) surfaces of pure W and W containing helium impurity
Authors: Qin Meng-Fei , Wang Ying-Min , Zhang Hong-Yu , Sun Ji-Zhong ,   School of Physics, Dalian University of Technology, Dalian 116023, China,   School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023, China
Published: September 2023

In the fusion irradiation environment, dislocation loop defects occurring under plasma-facing tungsten surface affect its mechanical properties and hydrogen/helium retention. This paper studies the dynamic behaviors of a <inline-formula><tex-math id="M13">\begin{document}$\langle 100\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M13.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M13.png"/></alternatives></inline-formula> loop with a radius of 1 nm under the W <inline-formula><tex-math id="M14">\begin{document}$(010)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M14.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M14.png"/></alternatives></inline-formula> surface by using molecular dynamics simulation at the atomic level. It is found that the dislocation loop direction, bulk temperature, depth, and helium atoms can greatly affect the motion of dislocation loops, showing that the <inline-formula><tex-math id="M15">\begin{document}$ {\boldsymbol{b}}/ / {\boldsymbol{n}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M15.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M15.png"/></alternatives></inline-formula> dislocation loop, where <inline-formula><tex-math id="M16">\begin{document}$ {\boldsymbol{b}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M16.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M16.png"/></alternatives></inline-formula> is the Burgers vector and <inline-formula><tex-math id="M17">\begin{document}$ {\boldsymbol{n}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M17.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M17.png"/></alternatives></inline-formula> denotes the surface normal direction, tends to move towards the surface and the <inline-formula><tex-math id="M18">\begin{document}$ {\boldsymbol{b}} \bot {\boldsymbol{n}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M18.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M18.png"/></alternatives></inline-formula> dislocation loop tends to stay in the material. In the course of its migration, the habit plane of dislocation loop may change and the internal stress decreases gradually. The probability of a <inline-formula><tex-math id="M19">\begin{document}$ {\boldsymbol{b}}/ / {\boldsymbol{n}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M19.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M19.png"/></alternatives></inline-formula> dislocation loops escaping from the surface is over 90% when the temperature is higher than 800 K and their initial depth is less than 5 nm. The <inline-formula><tex-math id="M20">\begin{document}$ {\boldsymbol{b}} \bot {\boldsymbol{n}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M20.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M20.png"/></alternatives></inline-formula> dislocation loop can escape from the surface when the temperature is 800 K and the initial depth is less than 2 nm. It is found that <inline-formula><tex-math id="M21">\begin{document}$\langle 100\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M21.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M21.png"/></alternatives></inline-formula> dislocation loops decompose into <inline-formula><tex-math id="M22">\begin{document}${1 \mathord{\left/ {\vphantom {1 2}} \right. } 2}\langle 111\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M22.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20230651_M22.png"/></alternatives></inline-formula> dislocations at elevated temperatures. Helium atoms impede the migration of dislocation loops and increase their retention time. The existence of dislocation loops results in the uneven distribution of helium atoms under the W surface, and will potentially affect the surface morphology of tungsten.