Multiscale twin hierarchy in NiMnGa shape memory alloys with Fe and Cu

X-ray microdiffraction and scanning electron microscopy studies reveal 10M martensitic structure with a highly correlated multiscale twin hierarchy organization in NiMnGaFeCu shape memory alloys. High compatibility is found at the twin interfaces resulting in a highly correlated twinned lattice orientation across several laminate levels. The lattice unit cell is described as monoclinic I-centered with a =4.28Aa, b =4.27Aa, c =5.40Aa, gamma =78.5 degree . The modulation is found parallel to the b axis. Thin tapered needle-like lamellae and branching are observed near the twin boundaries.