Pseudoelastic deformation and size effects during in situ transmission electron microscopy tensile testing of NiTi

0387724 - ÚFM 2013 RIV GB eng J - Journal Article
Manchuraju, S. - Kroeger, A. - Somsen, C. - Dlouhý, Antonín - Eggeler, G. - Sarosi, P. M. - Anderson, P. M. - Mills, M. J.
Pseudoelastic deformation and size effects during in situ transmission electron microscopy tensile testing of NiTi.
Acta Materialia. Roč. 60, 6-7 (2012), s. 2770-2777. ISSN 1359-6454. E-ISSN 1873-2453
Institutional support: RVO:68081723
Keywords : martensitic phase transformation * In Situ TEM * Shape memory alloys * Crystallographic theory of martensite
Subject RIV: JG - Metallurgy
Impact factor: 3.941, year: 2012

The stress-induced B2-B19' transformation in aged 51 at.% NiTi was investigated using in situ straining transmission electron microscopy (TEM). Increased applied strain along [1 1 0](B2) transforms B2 into plates containing B19' variants that are related by a (1 1 0)(B2) compound twin plane. This atypical twin plane is explained by relaxing the invariant plane constraint in the crystallographic theory of martensite (CTM) to an invariant line constraint. The relaxation is rationalized from the thin foil geometry. The relaxed CTM approach, coupled with conditions to maximize transformation strain along the loading axis and minimize elastic energy, predicts the observed twin interface, diffraction patterns, and interface with the B2 austenite. These results demonstrate subtleties in interpreting thin foil TEM results regarding martensitic transformations, and translating those results to bulk response. (C) 2012 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.
Permanent Link: http://hdl.handle.net/11104/0216831