Macroscopic austenite-martensite transition zones in thin superelastic NiTi wires subjected to stretching, twisting and their combination were reconstructed via diffraction/scattering computed tomography. The method allows to visualize spatial distributions of both phases from a series of X-ray diffraction scans. A cone-shaped, radially symmetric transformation front was observed in stretched wire both with and without applied pre-twist. Twisting of a pre-stretched wire (with a cone-shaped transformation band front already developed) led to the formation of a multi-prong localization morphology recognizable on the surface. Transition zones in these cases are highly heterogeneous complex 3D objects exhibiting distinct phase gradients; the longitudinal size of the zones is comparable with the wire diameter. In contrast, localized martensitic strips parallel with wire axis and with a wedge-like cross-section appeared on the surface of the wire which was twisted only. We discuss the observed localization patterns with respect to current computational simulations and micromechanical models.

通过衍射/散射计算机断层扫描重建超弹性镍钛细丝中的宏观奥氏体 - 马氏体过渡区，经受拉伸、扭曲及其组合。该方法允许从一系列 X 射线衍射扫描中可视化两个相的空间分布。在施加和未施加预扭曲的拉伸丝中观察到锥形、径向对称的变换前沿。预拉伸线的扭曲（已经形成锥形转变带前沿）导致形成可在表面识别的多叉定位形态。在这些情况下，过渡区是高度异质的复杂 3D 对象，表现出不同的相位梯度；区域的纵向尺寸与线径相当。相比之下，仅在绞合的线材表面出现平行于线轴并具有楔形横截面的局部马氏体条带。我们讨论了与当前计算模拟和微机械模型相关的观察到的定位模式。