Entropic interaction between fluctuating twin boundaries. (November 2015)

• Record Type: Journal Article
• Authors: Chen, Dengke; Kulkarni, Yashashree
• Is Part Of: Journal of the mechanics and physics of solids. Volume 84(2015:Nov.)
• Page Start: 59
• Page End: 71
• Publication Date: 2015-11
• Subjects: Coherent twin boundaries -- Thermal fluctuations -- Entropic interaction -- Molecular dynamics -- Shear coupled grain boundaries; Mechanics, Applied -- Periodicals; Solids -- Periodicals; Mechanics -- Periodicals; Mécanique appliquée -- Périodiques; Solides -- Périodiques; Mechanics, Applied; Solids; Periodicals; 531.05
• DOI: 10.1016/j.jmps.2015.07.001
• Languages: English
• ISSNs: 0022-5096

Abstract

Abstract: Nanotwinned metals have opened up exciting avenues for the design of high-strength, high-ductility materials owing to the extraordinary properties of twin boundaries. The recent advances in the fabrication of nanostructured materials with twin lamella on the order of a mere few atomic layers call for a closer examination of the stability of these structural motifs, especially at high temperatures. This paper presents a study of the entropic interaction between fluctuating twin boundaries by way of atomistic simulations and statistical mechanics based analysis. The simulations reveal that fluctuations of twin boundaries are considerably enhanced in the presence of adjoining twin boundaries as their spacing, d, decreases. In addition, the theoretical analysis shows that fluctuating twin boundaries indeed exhibit an attractive entropic interaction which enhances their thermal fluctuations and that the entropic force decreases as 1 / d 2 . This finite temperature interaction between twin boundaries is fundamentally distinct from the well-known repulsive entropic interaction followed by fluctuating lipid membranes as well as many crystalline membranes and interfaces. This rather surprising attraction between fluctuating twin boundaries is attributed to their shear coupled normal motion.