Four-dimensional observation of ductile fracture in sintered iron using synchrotron X-ray laminography

Abstract

Synchrotron X-ray laminography was used to examine the time-dependent evolution of the three-dimensional (3D) morphology of micropores in sintered iron during the tensile test. 3D snapshots showed that the networked open pores grow wider than 20 µm along the tensile direction, resulting in the internal necking of the specimen. Subsequently, these pores initiated the cracks perpendicular to the tensile direction by coalescing with the surrounding pre-existing microvoids or with the secondary-generated voids immediately before fracture. Topological analysis of the barycentric positions of these microvoids showed that they form the two-dimensional networks within the ∼20 µm of radius area. These observations strongly indicate that the microvoid coalescence could occur on shear planes formed close to the enlarged open pores or between closed pores by strain accumulation and play an important role in the crack initiation.

Use of X-ray CT Imaging to Quantitatively Analyze the Effects of the Pore Morphology on the Tensile Properties of CP-Ti L-PBF Materials

“…15,16) In this context, Ozaki et al conducted high-intensity X-ray computed tomography (CT) imaging of pure iron-sintered bodies with different porosities and quantified the pore morphologies and arrangements using persistent homology within the topology. 17,18) In addition, it has been reported that crystal orientations can be obtained using an inverse pole figure that is based on the analysis of electron backscatter diffraction (EBSD) patterns. As a result, quantification of the statistical distribution of the crystal orientation as an inverse pole figure-like pole distribution is possible.…”