Dresden 2011 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 41: Topical Session Diffussionless Transformations II

MM 41.1: Talk

Thursday, March 17, 2011, 16:15–16:30, IFW D

(contribution withdrawn) Martensitic transformations in thin epitaxial films of the NiTi shape memory alloy — •Joerg Buschbeck, Jason Kawasaki, Alexander Khozanov, and Chris Palmstrom — ECE Department, University of California, Santa Barbara, US

Phase formation and martensitic transformations are studied on molecular beam epitaxy (MBE) grown Ni-Ti films over a wide range of Ti contents from 43 to 56 at.%. Ordering of the B2 phase is investigated as function of growth temperature. Lattice mismatch stabilizes the NiTi B2 phase in a tetragonally distorted structure. Despite the epitaxial interface constraining the only 35 nm thick films, we observe reversible martensitic transformations in temperature dependent X-ray diffraction and resistivity. Ti-content and epitaxial interface control the transformation temperatures. In similarity to the B2-R-B19' sequence in bulk, a two-stage martensitic transformation is observed. This transformation occurs without tilt of the normal lattice vector, as temperature dependent reciprocal space mappings show.