Thermoelastic martensitic transition and shape memory effect in Ti2NiCu alloy at micro- and nanoscale

Abstract

Problem. An important fundamental problem in condensed matter physics is the study of the physical properties of various materials at the nanoscale size. A deep understanding of size effects is necessary when studying multifunctional solid materials with phase transitions and giant effects, such as magnetocaloric, elastocaloric, shape memory effect (SME). Goal. Direct experimental study of the manifestation of the thermoelastic martensitic transition and the accompanying SME in the Ti2NiCu alloy at the nanoscale in transmission electron microscope (TEM). Result. For the first time in a TEM during heating and cooling, the observed SME in nanocomposite amorphous-crystalline Ti2NiCu samples while observing the evolution of the structure of martensitic twins and the shape of changes. Investigations are carried out on wedge-shaped samples with variable thickness from 200 to 20 nm, in the form of a composite bimetallic nano-actuator, using the original method of local etching and polishing with a focused ion beam (FIB). Practical significance. These findings open the pathway for size limit indications and regime modulations where the alloy-based nanomechanical devices can be tuned to operate more efficiently.