Local relative density fluctuation in the early stage of a sintered glass sphere compact determined by X-ray computed tomography.

• The microstructure characterization of a glass-sintered compact is presented based on local density fluctuation. • Local density fluctuation is assessed based on 3D data as a function of observation region. • The degree of heterogeneity of the microstructure is calculated by the coarseness parameter. • Local density fluctuation is represented by a normal probability distribution function. • The coarseness parameter is dependent on the observation region. The relative density of a sintered glass-powder compact varies at the local level due to its heterogeneous nature, which makes its characterization essential. In this work, high-resolution X-ray computed tomography (XCT) was used to quantitatively characterize the local relative density fluctuation of a sintered glass compact in its initial stage. The degree of heterogeneity of the microstructure was calculated taking into account the coarseness parameter. With a basis of 23,500 particles scanned in the representative volume element (RVE), the local environment was subdivided into three different groups of particles, represented by a cubic cell with a volume equivalent to that of approximately 600, 80 and 10 spherical particles with a diameter of 80 μm. Independent of the particle group analysed, we found that the maximum of the local relative density distributions, which could be described by a normal distribution function, always occurs around the relative density of the RVE. However, the fluctuation of the data showed a considerable change regarding the width, which increases as the volume of the analysed group of particles decreases, suggesting that particle packing is more heterogeneous on a small scale. In particular, we observed that the heterogeneity of the microstructure for the RVE under consideration becomes pronounced for groups of approximately 10 to 80 particles. Image, graphical abstract [ABSTRACT FROM AUTHOR]