Measurements of plastic displacement gradient components in three dimensions using marker particles and synchrotron X-ray absorption microtomography

A universal method is presented for characterising the three-dimensional (3D) plastic displacement gradient field in bulk materials that contain particles or voids observable by X-ray tomography. Millimetre sized samples are investigated by absorption contrast microtomography using high intensity X-rays from a synchrotron source. The positions of dispersed marker particles are determined as a function of imposed strain. The particle diameter can be in the micrometre range, and the volume fraction can be less than 1%. The method is demonstrated by evaluation of compression deformation of a cylindrical Al specimen containing W marker particles. By interpolating the displacement gradient components determined at each particle on a 30x30x30 μm3 grid, 3D maps of the displacement gradient components are obtained with a resolution of 10-2 in each component. Limitations of the method are discussed, and the potential for application in materials science is outlined