Ni-Ti AND Ni-Mn-Ga NANOCRYSTALLINE SHAPE

MEMORY ALLOYS AND COMPOSITES FOR NEXT GENERATION SENSORS

AND ACTUATORS

Teodor M. BreczkoLab of Functional Materials and

Nanotechnology of University of Warmia and Mazury, Olsztyn, Poland

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.

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).

Experimental results

50

100

150

200

250

0 10 20 30 40 50

0.5

1.0

1.5

2.0

RM

S m

icro

stra

in x

10

-3

Changes in RMS micro-strains 21/2 *10-3 with number of thermal and

mechanical loading.

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.

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.

tem

pera

ture

, K

x

FERROMAGNETIC SHAPE MEMORY HEUSLER ALLOYS Ni2+xMn1-xGa

Partial substitution of Mn with Ni increases the

temperature of structural transition TM and decreases

the Curie temperature TC resulting in their

coincidence at x ~ 0.19

TM

TC

TP

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

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

cooling and heating

A

B C

A

B C

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

Combined optical measurements of

the deformation and microstructural observations

provide information on the details of

material behaviour during phase

transition

martensite austenite

OBSERVATION OF DS REALIGNMENT DURING MARTENSITE-AUSTENITE TRANSFORMATION IN Ni-Mn-Ga ALLOY

(video film fragments)

Sample size 200x800 m

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

302 К 322 К

323 К 325 К

Melt-spun Ni-Mn-Ga ribbons

thickness 30 m , length 10-30 mm

initial shape after heating

SHAPE MEMORY EFFECT IN NANOCRYSTALLINE Ni-Mn-Ga RIBBON

Simultaneous observation of the martensite and magnetic domain structure of polycrystalline texturized sample

having elongated grains

Displacement 0,6 – 5 mm,

Force – up to 1000 Newtons,

Frequency 300 – 1000 Hz

MAGNETICALLY CONTROLLED ACTUATORS BASED ON Ni-Mn-Ga

(ADAPTAMAT)

A5-2

A06-3

A1-2000

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.

IMEM-CNR, Magnetic Materials Department, Parma, Italy (Dr

Franca ALBERTINI) - magnetic properties of nanocrystalline

materials

Laboratoire d'Electrotechnique de Grenoble, France, (Dr.

Orphee CUGAT) - application of nanocrystalline materials in

MAGMAS  

Lab of Functional Materials and Nanotechnology of University of Warmia and Mazury, Olsztyn, Poland (Prof. T. BRECZKO) -

X-ray, MFM

A.F.Ioffe Institute, Russian Academy of Sciences (Prof. V.I.

BETEKHTIN) - structural studies  

Institute of Powder Metallurgy, Minsk, Belarus ( Dr. N.M.

CHIGRINOVA) - multilayered structures  

Institute of Radioelectronics, Russian Academy of Sciences, Moscow (Prof. V.G. SHAVROV)

– composite structures

Tver State University, Russia (Prof. R.M. GRECHISHKIN),

domain structure studies

Dept. Fisica Unversitat de Girona, Spain (Dr. Joan Josep SUNOL) - mechanical alloying of nanocrystalline materials

Institute of Metal Physics of Ural Division of Russian Academy of Sciences in Ekaterinburg (Prof.

V.G. PUSHIN) - electron microscopy)  

THE TEAM

C.V.Kurdyumov Institute for Metal Physics and Functional Materials, Moscow (Prof. A.M.

GLEZER) - thin film preparation  

St Petersburg State Technical University

(prof.. A. I. MELKER)- computer simulations