Microstructure, crystallography, and shape memory effect in equiatomic NbRu

The microstructure and crystallography of equiatomic NbRu were examined by transmission electron microscopy (TEM) and electron diffraction. This alloy exhibits a highly twinned microstructure identical to that in the similar TaRu system. Electron diffraction demonstrates that, like TaRu, the room-temperature crystal structure of NbRu is not orthorhombic as had been previously reported, but is instead monoclinic. The transformation which forms this monoclinic structure produces a high concentration of antiphase domain boundaries and some δ-domain boundaries within the twinned microstructure. The shape memory effect in NbRu was demonstrated by reheating bent samples to above the high-temperature tetragonal-to-cubic transformation temperature and observing the decrease in bend angle. Initial tests demonstrate a strain recovery of 4% at the tensile surface. (orig.)