Teodor M. Breczko

1. Ni-Ti AND Ni-Mn-Ga NANOCRYSTALLINE SHAPE MEMORY ALLOYS AND COMPOSITES FOR NEXT GENERATION SENSORS AND ACTUATORS Teodor M. Breczko Lab of Functional Materials and Nanotechnology of University of Warmia and Mazury, Olsztyn, Poland

2. SHAPE MEMORY ALLOYS(SMA) Rapidly quenched melt-spun ribbons of Ti-Ni, Ti50Ni50-xFex, Ti50Ni50-yCoy and Ti50Ni50-zCuz shape memory alloys were obtained and studied with the aid of X-ray diffraction, TEM and magnetic susceptibility and resistivity measurements. The formation of amorphous, nanocrystalline, and submicron-grained structures was demonstrated.

3. The X-ray diffraction studies show that, depending on the composition and the cooling rate, the melt-quenched Ni-Ti-Cu alloys can be prepared in the amorphous (curves 1,2), mixed amorphous-nanocrystalline (3),and submicrocrystallinestates (4,5).

4. Experimental results Changes in RMS micro-strains 21/2 *10-3 with number of thermal and mechanical loading.

5. High mechanical strength and plasticity of rapidly quenched ribbons may be obtained alongside with narrow temperature hysteresis of the shape memory effect and high durability necessary for a number of applications. The Cu-doped melt-spun ribbons are found to be most promising for sensors and actuators operating in the vicinity of room temperature. Temperature sensor on the base of Ti-Ni-Cu melt-spun ribbon ring actuator with a diameter D = 2 mm (movable contact not shown). Operation temperature T = 70oC.

6. FERROMAGNETIC SHAPE MEMORY HEUSLER ALLOYS (FSMA) Ferromagnetic Ni-Mn-Ga and Co-Ni-Ga Heusler alloys attract attention due to their unique combination of thermoelastic martensitic transformation and ferromagnetism as well as potential applications in new types of sensors and actuators. Rapidly quenched ribbons (RQR) of these alloys with nano- and microcrystalline structure controlled by annealing are of interest in connection with the possibility of their shape memory control with the aid of magnetic field.

7. FERROMAGNETIC SHAPE MEMORY HEUSLER ALLOYS Ni2+xMn1-xGa TM Partial substitution of Mn with Ni increases the temperature of structural transition TM and decreases the Curie temperatureTC resulting in their coincidence at x ~ 0.19 TP TC

8. Observations in polarized light provide new dimensions to the analysis of the martensite structure. The optical contrast originates from anistropic reflectance of martensite and depends on the orientation of the crystal c-axis with respect to the plane of light polarization. Martensite structure at the surface of a mechanically polished polycrystalline Ni2.16Mn0.84Ga sample as observed in polarized light

9. Video showing the appearance and disappearance of martensite phase in Ni2.16Mn0.84Ga alloy in the course of cooling and heating

10. martensite austenite Combined optical measurements of the deformation and microstructural observations provide information on the details of material behaviour during phase transition Microstructure of Ni2.16Mn0.84Ga at RT and at Т = 370 К Arrows and letters indicate the points of intersection of martensite boundaries with a rectangular reference grid on the sample surface and their inflection on transition to the austenite state

11. OBSERVATION OF DS REALIGNMENT DURING MARTENSITE-AUSTENITE TRANSFORMATION IN Ni-Mn-Ga ALLOY (video film fragments) Initially the Ni2.16Mn0.84Ga microcrystal is in the martensitic state characterized by 180-degree magnetic DS. On heating the alloy transforms into a cubic magnetically soft austenite phase with negligible stray fields on the sample surface • Sample size 200x800 mm

12. Melt-spun Ni-Mn-Ga ribbons thickness 30 mm , length 10-30 mm

13. SHAPE MEMORY EFFECT IN NANOCRYSTALLINE Ni-Mn-Ga RIBBON initial shapeafter heating

14. Simultaneous observation of the martensite and magnetic domain structure of polycrystalline texturized sample having elongated grains

15. MAGNETICALLY CONTROLLED ACTUATORS BASED ONNi-Mn-Ga (ADAPTAMAT) A5-2 A06-3 Displacement 0,6 – 5 mm, Force – up to 1000 Newtons, Frequency 300 – 1000 Hz A1-2000

16. RESULTS • 1. The new trend in magnetic shape memory control is developed on the basis of “classical’ shape memory. The reversible martensitic transition by magnetic field at constant temperature is demonstrated. • 2. One- and two way shape memory control of Ni-Mn-Fe-Ga nanocrystalline samples is shown. The recoverable strain 3% for one-way and 1,4% for two way shape memory is measured. • 3. The results can be applied to MEMS, NEMS and MAGMAS devices design.

17. THE TEAM Laboratoire d'Electrotechnique de Grenoble, France, (Dr. Orphee CUGAT) - application of nanocrystalline materials in MAGMAS   IMEM-CNR, Magnetic Materials Department, Parma, Italy (Dr Franca ALBERTINI)- magnetic properties of nanocrystalline materials Dept. Fisica Unversitat de Girona, Spain (Dr. Joan Josep SUNOL) -mechanical alloying of nanocrystalline materials A.F.Ioffe Institute, Russian Academy of Sciences (Prof. V.I. BETEKHTIN) - structural studies Lab of Functional Materials and Nanotechnology of University of Warmia and Mazury, Olsztyn, Poland (Prof. T. BRECZKO) - X-ray, MFM C.V.Kurdyumov Institute for Metal Physics and Functional Materials, Moscow (Prof. A.M. GLEZER) - thin film preparation   Institute of Metal Physics of Ural Division of Russian Academy of Sciences in Ekaterinburg (Prof. V.G. PUSHIN) - electron microscopy) Institute of Powder Metallurgy, Minsk, Belarus ( Dr. N.M. CHIGRINOVA) - multilayered structures St Petersburg State Technical University (prof.. A. I. MELKER) - computer simulations Tver State University, Russia (Prof. R.M. GRECHISHKIN),domain structure studies Institute of Radioelectronics, Russian Academy of Sciences, Moscow (Prof. V.G. SHAVROV) – composite structures