In metals, the difference of deformability of different grains in an aggregate can be absorbed by inhomogeneous deformation. Three-dimensional (3D) non-destructive methods with a high spatial resolution is necessary for characterization of such microscale inhomogeneous deformation. This manuscript describes the two major methods of internal 3D strain measurement: the microstructural features tracking (MFT) and digital volume correlation (DVC), on the basis of four-dimensional (4D, i.e. 3D + time) observation by means of synchrotron radiation tomography (SRCT). Localized strain distributions obtained by these advanced methods are related to the deformed microstructures, allowing a discussion regarding the mechanisms of internal deformation in the true 3D condition of materials.

在金属中，聚集体中不同晶粒的可变形性差异可以通过不均匀变形来吸收。具有高空间分辨率的三维（3D）非破坏性方法对于表征此类微尺度非均匀变形是必要的。该手稿描述了内部3D应变测量的两种主要方法：微结构特征跟踪（MFT）和数字体积相关性（DVC），这是基于通过同步辐射层析成像进行的四维（4D，即3D +时间）观察（SRCT）。通过这些先进方法获得的局部应变分布与变形的微观结构有关，从而可以讨论在真实材料的3D条件下内部变形的机理。