Issue 4, 2014

Direct observation of hierarchical nucleation of martensite and size-dependent superelasticity in shape memory alloys

Abstract

Martensitic transformation usually creates hierarchical internal structures beyond mere change of the atomic crystal structure. Multi-stage nucleation is thus required, where nucleation (level-1) of the underlying atomic crystal lattice does not have to be immediately followed by the nucleation of higher-order superstructures (level-2 and above), such as polysynthetic laths. Using in situ transmission electron microscopy (TEM), we directly observe the nucleation of the level-2 superstructure in a Cu–Al–Ni single crystal under compression, with critical super-nuclei size L2c around 500 nm. When the sample size D decreases below L2c, the superelasticity behavior changes from a flat stress plateau to a continuously rising stress–strain curve. Such size dependence definitely would impact the application of shape memory alloys in miniaturized MEMS/NEMS devices.

Graphical abstract: Direct observation of hierarchical nucleation of martensite and size-dependent superelasticity in shape memory alloys

Supplementary files

Article information

Article type
Communication
Submitted
02 Oct 2013
Accepted
08 Nov 2013
First published
26 Nov 2013

Nanoscale, 2014,6, 2067-2072

Direct observation of hierarchical nucleation of martensite and size-dependent superelasticity in shape memory alloys

L. Liu, X. Ding, J. Li, T. Lookman and J. Sun, Nanoscale, 2014, 6, 2067 DOI: 10.1039/C3NR05258C

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