Fundamental Limitations on Miniaturization of Shape-Memory Micromechanical Devices. Thermoelastic Martensite Transformation on Micro-, Nano-, and Mesoscales

Abstract

TEM measurements are used to experimentally study thermoelastic martensite transformation in Ti₂NiCu tapered plates. The martensite phase is observed at room temperature in the Ti₂NiCu alloy when the plate thickness decreases to, at least, 80 nm, and the austenite phase is observed at smaller thicknesses. It is shown that the temperature of thermoelastic martensite transition in the Ti₂NiCu alloy decreases with a decrease in the thickness of the plate, the transition is blocked at a thickness of less than 20 nm, and a hysteresis dependence is observed. Possible physical and technological reasons for blocking of the martensite phase transition on nanoscale and fundamental limitations on the sizes of micromechanical devices based on the shape-memory Ti₂NiCu alloy are considered.