On the impact of thermal treatments on shape memory properties of [001] orientated Fe-Ni-Co-Al-Ti single crystals


Viktor Remich-1, Cesar Sobrero-3, Yuri I. Chumlyakov-2, Christian Lauhoff-1, Thomas Niendorf-1, Philipp Krooß-1

1-Institut für Werkstofftechnik, Universität Kassel, Mönchebergstraße 3, 34125 Kassel, Germany

2-Siberian Physical-Technical Institute TSU, Tomsk State University, 1 Novosobornaya Sq., 634050 Tomsk, Russia

3-Institute of Physics Rosario, CONICET- Universidad Nacional de Rosario, Blvd. 27 de Febrero 210 Bis, 2000 Rosario, Argentina

e-Mail: remich@uni-kassel.de


In both, research and industry, shape memory alloys (SMAs) gain increasing attention due to their unique shape memory properties. SMAs can be used in many potential applications in the automotive, aerospace and construction sector. Conventional SMAs such as Ni-Ti feature promising material properties but suffer high pricing and complex processing routes. Here, on the other hand, the advantages of the Fe-based SMAs can be seen, as lower prices of the alloying elements and the existing industrial process routes for steel reduce the overall processing costs. Fe-based SMAs of the Fe-Ni-Co-Al-X-family currently show promising superelastic properties with a reversible strain of up to 13%. Nonetheless, the Fe-SMAs feature limitations of low cyclic stability and low transformation Temperatures. However, variations in the chemical composition, e.g. the addition of Ti, is seen to be capable to improve the functional material properties.
Thus, this study is focusing on the influence of heat treatments on the thermo-mechanical properties of Fe-Ni-Co-Al-Ti single crystal alloys. The goal is to find a heat treatment parameter window, in which the alloy shows complete reversibility upon heating and cooling between  170°C to +80°C. Besides, mechanical tests and transmission electron microscopy was used to characterize the y'-precipitates to identify the interrelationship between the thermo-mechanical functional material properties, the heat treatment parameters as well as the size and morphology of the y'-precipitates.