Texture development and deformation mechanisms during uniaxial straining of U-Nb shape-memory alloys

The shape-memory effect is well documented in uranium-niobium alloys near the alpha''-gamma degrees metastable phase boundary. In situ neutron diffraction measurements during uniaxial loading indicate that U-14 at.% Nb ( in the alpha'' monoclinic phase field) deforms by stress-induced twin reorientation. Alternatively, U-16 at.% Nb ( initially gamma degrees tetragonal) undergoes a stress-induced phase transformation to the alpha'' monoclinic phase. The crystallographic texture of the monoclinic phase of both compositions has been measured and qualitatively interpreted by considering the orientation relationship between the most favoured alpha'' variant and the parent phase. In addition, previously published observations of deformation structures within the shape-memory regime of a U-13 at.% Nb alloy are discussed within the context of the same model.