The mechanism of nanocrystalline structure formation in Ni3Al during severe plastic deformation

The microstructure evolution of the intermetallic compound Ni3Al during severe deformation by torsion under high quasi-hydrostatic pressure, which eventually results in the formation of a disordered nanocrystalline structure with a high level of internal stresses, was investigated as a function of the amount of shear strain. At the microstructural level, the crystals were first fragmented by the propagation of twins, then nanosized equiaxed crystallites with high misorientations were formed. At the macroscopic level, there is evidence that the cold-worked structure first formed at the sample surface and then propagated into the whole volume.