Shape memory alloys (SMAs) are smart materials that have drawn significant attention and interest in a broad range of commercial applications in recent years; this commercial development has been enabled by basic and applied research. The estimated global market of smart materials is over $40 billion by 2016 with annual growth rate of 13%. The SMAs used in actuating and other applications enable miniaturization and technical progress in automotive, aerospace, robotics, biomedical, industrial applications, etc. Most of the interesting functionality of SMAs, such as shape memory effect or superelasticity, is enabled and mediated by martensitic phase transformation and related ferroelastic martensite microstructure [1]. The typical example of SMA is Ni-Ti or nitinol, which found significant applications in medicine.


Fig. 1. The recoverable large deformation of shape memory alloys is enabled by their ferroelastic martensite microsctructure. Example of deformed Ni-Mn-Ga single crystal with three large microstructural domains (length of crystal is 20 mm).


[1] J. M. Jani, M. Leary, A. Subic, M. A. Gibson, Materials & Design 56 (2014) 1078.