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Final Report Summary - MIDAS (Micro and Nanoscale Design of Thermally Actuating Systems)

The Micro and Nanoscale Design of Thermally Actuating Systems – MIDAS was successful in joining research partners from four continents in the effort to develop actuating materials belonging to the shape memory alloy group.
Structured in several work packages and implying research and training via exchange of experimented and early stage researchers the project achieved its goals.
In the Structural optimization by Mechanical Alloying (MA) workpackage the partners were successful in the fabrication of shape memory alloys by sintering mechanically alloyed NiTi-based and Cu-based alloys and by presenting seminars as well as via transfer of knowledge between the partners. In their effort, the partners identified and prepared appropriate compositions and used the equipment available in the partner’s institutions, setting up opportunities for further collaboration and using the opportunities for training early stage researchers.
In the Structural control by plastic deformation (SPD) work package, the partners set new strategies for dry lubrication and efficient parts separation after ECAP forming that provided information for further small scale modifications introduced in a second version of these ECAP tools. Tests were run on on NiTi and Cu-based alloys and research experiments to assess the capability of ECAP processing of NiTi plates embedded in a metal matrix were performed. Thermomechanical processing involving rolling and different combinations of heat treatments have been tested and the corresponding transformation characteristics of the material have been analyzed by DSC and high/low temperature XRD. These results show that: (i) simply solubilized material does not present any evidence of austenite – martensite transformation, after heat treatment at 500ºC, a two-step transformation appears, involving intermediary R-phase and (iii) this two-step transformation is confirmed by non-ambient XRD .
In the Micro and nanoscale characterization work package differential scanning calorimetery with temperature range from -180 to +550ºC and electrical resistivity probes with temperature range between -120 and +140ºC, as well as internal friction (IF) has been used to determine phase transformation temperatures in several metamagnetic alloys as Ni-Mn-In (+ Co) , Ni-Mn-Sn (+Co), and in Ni-Mn-Ga-Cu. The total entropy change associated to the temperature-induced magneto-structural transformation shown by these alloys has been measured, and the magnetic and lattice contributions have been evaluated. FePd ferromagnetic shape memory alloys as well as Ti-based high temperature shape memory alloys have been manufactured and characterized in view of their utilization in practical applications.
In Welding and joining techniques for smart materials (WJ) workpackage laser welding was experimented on similar and dissimilar couples of alloys, with at least one component beeing NiTi. For joints of NiTi to CuAlMn a defect-free joint was obtained with complex microstructural features including macrosegregation phenomena and different types of solidification structures. This was the first known successful attempt of dissimilar joint NiTi to CuAlMn shape memory alloys.
In the Applicative design workpackage several applications have been developed, such as actuators, thermal regulators and nanotweezers. Model for actuation in bimorph architectures comprising at least one shape memory alloy layer have been analyzed. Samples of thermally controlled SME composite nanotweezers based on bilayered structures Ti2NiCu/Pt with dimension (20-30)x(15-10)x(1-2) μm and controlled gap about 1 μm have been developed. The actuation of nanotweezers by application of electric current is was made and theoretically modeling of the new system was done. Experimental tests of the new control system of nanotweezers have been performed. The gap of nanotweezers was actuated by short electric pulses and frequency of response was measured in SEM by direct recording of the current of electron beam focused on the gap. The actuation of nanotweezers with frequency as high as 7000 Hz have been detected directly under control current pules of 4 mA. Devices based on shape memory materials, as well as the design of new applications have been considered by the partners for future collaboration.
A significant number of papers that reflected the result of the collaborations as well as patents submitted at national level are also results of the MIDAS project. The partners are planning to continue the collaboration initiated through the MIDAS Project with joint application submitted to international calls (e.g. design of systems reducing the liquid He evaporation in its containers, development of elastocaloric systems based on shape memory alloys, nanoapplications based on shape memory alloys).

Reported by

UNIVERSITATEA POLITEHNICA DIN TIMISOARA
Romania

Subjects

Life Sciences
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