Grain refinement and amorphization in nanocrystalline NiTi micropillars under uniaxial compression

Abstract Microscale plastic deformation mechanisms of nanocrystalline NiTi micropillars with an average grain size (GS) of 65 nm are investigated by uniaxial compression. Cuboidal NiTi micropillars with uniform cross-sectional area along the height are manufactured by focused ion beam. It is found that the plastic deformation of the micropillars under compression is realized by localized shear band formation with large strain bursts, leading to significant amorphization and GS reduction from 65 nm to as small as 11 nm in the shear band. The experiment indicates that microfabrication by severe plastic deformation could be a promising manufacturing technology.