THE INFLUENCE OF ULTRASONIC MECHANICAL ACTIVATION ON CRYSTALLIZATION KINETICS AND MARTENSITIC TRANSFORMATIONS OF TiNi-BASED AMORPHOUS ALLOYS

The influence of ultrasonic mechanical activation on the amorphous alloys is practically unstudied. The influence of ultrasound on crystallization of TiNi-based amorphous alloy ribbons, their structure and properties formation has not been investigated up to the present moment. Being in the crystalline state, TiNi-based amorphous alloys experience the thermoelastic martensitic transformations, which are the basis for manifestation of unusual mechanical properties – shape memory effect. Amorphous shape memory alloys are the advanced materials that experience thermoelastic martensitic transformations after crystallization. Such materials are used as the basis for the creation of crystalline materials with the specified parameters of crystalline structure or for producing the amorphous and crystalline composites. The goal of this work is the study of ultrasonic mechanical activation influence on the crystallization kinetics and martensitic transformations of an amorphous shape memory alloy using the differential scanning calorimetry (DSC) method. The ultrasonic mechanical activation was carried out using two methods: in the waveguide of longitudinal ultrasonic vibrations and in the ultrasonic anvil. During the first method of the ultrasound mechanical activation, the amorphous ribbon was fixed in the waveguide of longitudinal vibrations and experienced ultrasonic irradiation of various durations. To initiate ultrasonic vibrations, the authors used the UZDN-2T ultrasonic low-frequency dispergator with the frequency of 22 kHz. During the second method, the amorphous ribbon is placed horizontally and the vertically placed waveguide is applied using contact process. Such method is used for the surface strengthening of metals and alloys. To initiate the ultrasonic vibrations, the authors used the UZG 1-1 ultrasonic generator. Ti₅₀Ni₂₅Cu₂₅ amorphous ribbons were selected as a subject of the study. Calorimetric measurements were carried out using the Mettler Toledo 822e differential scanning calorimeter. The obtained data showed that in the result of ultrasonic mechanical activation, temperatures and energies of crystallization and martensitic transformations change that can be the evidence of size reduction of a crystalline phase grain.