ESOMAT 2009, 05023 (2009)
DOI: 10.1051/esomat/200905023

Nonconventional production technologies for NiTi shape memory alloys

F. Neves^{1, 2}, F.M. Braz Fernandes¹, I. Martins², J.B. Correia², M. Oliveira², E. Gaffet³, T.-Y. Wang⁴, M. Lattemann^{5, 6}, J. Suffner^{5, 6} and H. Hahn<sup>5, 6

1</sup>  CENIMAT/I3N, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
²  LNEG, Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038 Lisboa, Portugal
³  NRG, UMR 5060 CNRS, UTBM, Site de Sévenans, F90010 - Belfort, France
⁴  AKCMM, The University of Sydney, NSW, Sydney 2006, Australia
⁵  Joint Research Lab Nanomaterials, TUD-FZK, 64287 Darmstadt, Germany
⁶  INT, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany

filipe.neves@ineti.pt

Published online: 1 September 2009

Abstract
The development of new production technologies for NiTi Shape Memory Alloys (SMAs) is always challenging. Recently, we introduced two powder metallurgical (PM) processing routes involving mechanical activation of elemental powder mixtures and densification through extrusion or forging. Those processes were named Mechanically Activated Reactive Extrusion Synthesis (MARES) and Mechanically Activated Reactive FOrging Synthesis (MARFOS). Heat treatments were performed in order to adjust the B2-NiTi matrix composition, yielding a microstructure consisting of a homogeneous dispersion of Ni₄Ti₃ precipitates embedded in nanocrystalline B2-NiTi matrix. In the present study, we demonstrate the viability of those PM processes for producing NiTi SMAs. With insitu X-ray diffraction and differential scanning calorimetry it is shown that B2-NiTi matrix undergo a B2↔R↔B19’ two-step phase transformation.

© Owned by the authors, published by EDP Sciences 2009