A new form of pseudo-elasticity in small-scale nanotwinned gold

C Deng and F Sansoz, EXTREME MECHANICS LETTERS, 8, 201-207 (2016).

DOI: 10.1016/j.eml.2015.12.004

Molecular dynamics simulations are used to show a new type of pseudo- elasticity and shape memory effects in small-scale nanotwinned metals. Nanotwinned Au thin-films and nanowires are found to achieve full recovery of up to 20% tensile and -6.25% compressive strains upon reverse loading when the twin boundaries make a special angle of 70.53 degrees from the principal axis. This phenomenon results in superelastic recoverable strains up to 5 times larger than the useful range of deformation that can be induced in some advanced bulk shape-memory- alloys and small-scale ceramics, with a tensile strength above 1 GPa. The pseudo-elastic behavior stems from a unique interplay between deformation twinning and slip in grains composed of non-1 1 1 free surfaces and discontinued twin boundary migration in those exposing only 1 1 1 free surfaces. This finding could open up new opportunities for small-scale nanotwinned metals as advanced materials for vibration damping and mechanical energy storage applications. (C) 2015 Elsevier Ltd. All rights reserved.

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