Twinned Structures in Magnetic Shape Memory Alloys (TWISTR)

The project deals with magnetic shape memory alloys, with Ni-Mn-Ga being a prototype example, which are interesting for their functionalities such as giant up to 12% magnetic field-induced strain. The key to material functionality is its ferroelastic twinned martensite microstructure. However, the usual spontaneously created microstructures show suboptimal performance, which is often far from the true material possibilities. We aim to develop the methods of twin microstructure control, i.e. creating permanent twin microstructures, resulting in significantly improved functional performance. The challenge will be atacked on all scales: on nanoscale we will study the intrinsic mobility of twins, on mesoscale we will study the mechanisms of twin formation and twin-twin and twin-defect interactions. Based on these studies we will design methods of twin microstructure control and evaluate on macroscale the resulting properties and improvement in the functional behavior. The ultimate aim is to develop twinned material with properties as close as possible to the theoretical limits.