Grain Size and Phase Transformation Behavior of TiNi Shape-Memory-Alloy Thin Film under Different Deposition Conditions.

Joohyeon Bae,Sunchul Huh,Hyomin Jeong,Jeonghyeon Yang,Jungpil Noh,Sangdu Yun,Hyunsuk Lee,Duckhyeon Seo

doi:10.3390/ma13143229

Abstract

TiNi shape-memory-alloy thin films can be used as small high-speed actuators or sensors because they exhibit a rapid response rate. In recent years, the transformation temperature of these films, manufactured via a magnetron sputtering method, was found to be lower than that of the bulk alloys owing to the small size of the grain. In this study, deposition conditions (growth rate, film thickness, and substrate temperature) affecting the grain size of thin films were investigated. The grain size of the thin film alloys was found to be most responsive to the substrate temperature.

Highlights

Based on the constituent elements, these materials are classified into TiNi, Cu, and Fe-based alloys, among which TiNi-based shape memory alloys are the most widely used owing to their excellent stability and corrosion resistance [7,8,9,10,11]
This study investigated the variations in the grain size and phase transformation characteristics of TiNi shape memory alloy thin films prepared using direct current (DC) magnetron sputtering, under different deposition conditions
Alloy thin films grown at low substrate temperatures were amorphous and capable of crystallizing through annealing at 873 K

Summary

Introduction

Shape memory alloys (SMAs) are commonly considered to be smart materials because they exhibit shape memory effects and hyper-elastic properties that are not observed in typical metals [1,2,3,4,5,6].These extraordinary properties are due to a temperature-dependent martensitic phase transformation from a low (martensite) to high (austenite) symmetric crystallographic structure upon cooling, and a reverse martensitic transformation in the opposite direction upon heating.Based on the constituent elements, these materials are classified into TiNi-, Cu-, and Fe-based alloys, among which TiNi-based shape memory alloys are the most widely used owing to their excellent stability and corrosion resistance [7,8,9,10,11]. Shape memory alloys (SMAs) are commonly considered to be smart materials because they exhibit shape memory effects and hyper-elastic properties that are not observed in typical metals [1,2,3,4,5,6]. These extraordinary properties are due to a temperature-dependent martensitic phase transformation from a low (martensite) to high (austenite) symmetric crystallographic structure upon cooling, and a reverse martensitic transformation in the opposite direction upon heating. A fast response time is essential for the development of high-speed actuators or sensors

Methods

Results

Discussion

Conclusion