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Martensite adaption through epitaxial nano transition layers in TiNiCu shape memory alloys
Author(s) -
Dankwort Torben,
Strobel Julian,
Chluba Christoph,
Ge Wenwei,
Duppel Viola,
Wuttig Manfred,
Quandt Eckhard,
Kienle Lorenz
Publication year - 2016
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s160057671600710x
Subject(s) - materials science , shape memory alloy , martensite , austenite , transmission electron microscopy , metallurgy , orthorhombic crystal system , high resolution transmission electron microscopy , epitaxy , composite material , crystallography , nanotechnology , crystal structure , microstructure , layer (electronics) , chemistry
Titanium‐rich TiNiCu shape memory thin films with ultralow fatigue have been analysed for their structural features by transmission electron microscopy. The stabilization of austenite (B2) and orthorhombic martensite (B19) variants epitaxially connected to Ti 2 Cu‐type precipitates has been observed and found responsible for the supreme mechanical cycling capability of these compounds. Comprehensive ex situ and in situ cooling/heating experiments have demonstrated the presence of an austenitic nanoscale region in between B19 and Ti 2 Cu, in which the structure shows a gradual transition from B19 to B2 which is then coupled to the Ti 2 Cu precipitate. It is proposed that this residual and epitaxial austenite acts as a template for the temperature‐induced B2↔B19 phase transition and is also responsible for the high repeatability of the stress‐induced transformation. This scenario poses an antithesis to residual martensite found in common high‐fatigue shape memory alloys.