Interaction of irradiation-induced prismatic dislocation loops with free surfaces in tungsten

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• 作者：Jan Fikar^a ; ^fikar@ipm.cz ; Roman Grö ; ger^a ; Robin Schä ; ublin^b
• 关键词：Prismatic dislocation loop ; Image force ; Radiation damage ; Molecular statics ; Tungsten
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：393
• 期：Complete
• 页码：186-189
• 全文大小：451 K
• 卷排序：393

文摘

The prismatic dislocation loops appear in metals as a result of high-energy irradiation. Understanding their formation and interaction is important for quantification of irradiation-induced deterioration of mechanical properties. Characterization of dislocation loops in thin foils is commonly made using transmission electron microscopy (TEM), but the results are inevitably influenced by the proximity of free surfaces. The prismatic loops are attracted to free surfaces by image forces. Depending on the type, size and depth of the loop in the foil, they can escape to the free surface, thus invalidating TEM observations and conclusions. In this article small prismatic hexagonal and circular dislocation loops in tungsten with the Burgers vectors 1/2〈111〉 and 〈100〉 are studied by molecular statics simulations using three embedded atom method (EAM) potentials. The calculated image forces are compared to known elastic solutions. A particular attention is paid to the critical stress to move edge dislocations. The escape of the loop to the free surface is quantified by a combination of atomistic simulations and elastic calculations. For example, for the 1/2〈111〉 loop with diameter 7.4 nm in a 55 nm thick foil we calculated that about one half of the loops will escape to the free surface. This implies that TEM observations detect only approx. 50% of the loops that were originally present in the foil.