Preparation of single crystal of TiNi alloy and its shape memory performance

Abstract

The unidirectional solidification equipment based on Bridgman method with high temperature gradient was designed, and the single crystal of Ti-50.0at%Ni alloy was successfully fabricated by this equipment as well as a selective growing zigzag-shaped crystallizer and a steady growth container that were made of electro graphite. The microstructure of single crystal sample was studied by means of Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS); the orientation of single crystal was measured by X-ray technology; the phase transformation points were determined by Differential Scanning Calorimetry (DSC). It is resulted that, the single crystal of TiNi shape memory alloy (SMA) can be prepared with a set of suitable process parameters; the microstructure of the single crystal obtained in this study is dendritic, there is Ti 2 Ni intermetallic between the dendrites, the angle between the orientation of single crystal and [111] plane is about 15 degree; the shape memory performances are improved obviously and the maximum recoverable strain reaches 10%.