RAPIDLY QUENCHED AMORPHOUS-CRYSTALLINE Ti50Ni25Cu25 ALLOY RIBBONS WITH THE TWO-WAY SHAPE MEMORY EFFECT FOR THE MICROMECHANICAL DEVICES

Using the single roller melt-spinning technique, thin Ti₅₀Ni₂₅Cu₂₅ alloy ribbons (at. %) in the amorphous-crystalline state (thickness of 30÷50 micron and width from 1 to 2 mm) were produced. The study of the obtained samples using the scanning electronic microscopy and the X-ray diffraction phase analysis showed that, at the cooling rates of 105÷106 K/s, a ribbon was represented by a laminated amorphous-crystalline composite material, which showed a two-way shape memory effect (TWSME) behavior with the bending deformation without any additional thermo-mechanical treatment. It is determined that the rapidly quenched amorphous-crystalline composite forming is caused by the realization of shape memory effect through the martensitic transformations in the crystalline layer. The authors proposed the qualitative structural model of a composite material consisting of an amorphous layer and a pseudoplastically stretched crystal layer with the shape memory effect, which describes correctly the mechanical behavior of a composite under the TWSME. The capacity of developed amorphous-crystalline composite for the two-way bending deformation was used to create the miniature functional elements with the two-way shape memory for bending for the multipurpose micromechanical devices. In particular, on the basis of rapidly quenched Ti₅₀Ni₂₅Cu₂₅ laminated amorphous-crystalline composite alloy having the reversible bending shape memory with the crystal layer thickness of 10 µm and the amorphous layer thickness of 30 µm, the micro-tweezers with the gap adjustable in the range from 10 to 500 microns and more depending on the size of captured object were designed and produced. The developed tweezer-based device can be used to pick and move micro-objects of different origin with the size from units to hundreds of microns. The authors demonstrated the prospects of the developed amorphous-crystalline composite with the TWSME for the creation on its base of the miniature functional elements with the reversible bending shape memory for the micromechanical devices in various engineering fields such as microelectronics, robotics or microbiology.