Martensitic structures and deformation twinning in the U–Nb shape-memory alloys

An investigation of the microstructures of four U–Nb alloys has been conducted. The nominal Nb contents are 5, 9, 13 and 18at.% (approximately 2, 4, 5.5 and 8 wt%). The self-accommodating twin structures have been characterized and considered in terms of the lattice parameters of the martensite phases as well as the tetragonal distortion associated with the previously proposed intermediate γ0 phase. In addition, active deformation twinning systems during deformation of the U–13 at.% Nb shape-memory alloy have been identified and are discussed with respect to the α'' monoclinic distortion and ease of propagation in the microstructure.