Fig. 1 Schematic of the XCT process

Fig. 2. Three-dimensional reconstructed topography of powders with different particle sizes: a 200 μm; b 210 μm; c 95 μm; d 40 μm [17]

Fig. 3 a Cavities in AlSi10Mg particles; b 2D slices; c 3D reconstruction structure of cavities in particles; d distribution of the cavity size [19]

Fig. 4 CP-Ti implants with different porosity (P): a photographs, P?=?23%; b micro-CT images, P?=?41%; c SEM, P?=?61%; d optical micrographs, P?=?76% [20]

Fig. 5 A test artifact made by AM [28]

Fig. 6 CAD model a and measured geometry sizes b of the test artifact [30]

Fig. 7 CAD variance analysis of facial implant built by LPBF [9]

Fig. 8 Examples of XCT datasets. a Ti6Al4V sample with a voxel size of 9.9 μm; b the edge and the center of the same sample with a voxel size of 2.1 μm [39]

Fig. 9 CT view of porosity varying with the direction of construction. a, b : two directions and c one cropped view to emphasize the directionality of the porosity trails [42]

Fig. 10 XCT reconstruction shows the density distribution of Ti6Al4V alloy samples under different laser power [46]

Fig. 11 Pores (dark regions) observed along three principal axes and in 3D projection [48]

Fig. 12 CT characterization of 3D. a, b single-layer defect and c, d multiple layers defect morphologies in different directions [50]

Fig. 13 a Peak 1 sample fabricated with Ip?=?200 A and Ib?=?60 A; b an original scan tomogram of the red area in a ; c the reconstructed image of the blue area in b ; for better visualization, d the image of c without the SSPs; e the image of the yellow area in d [52]

Fig. 14 a Aspect ratio (AR) and sphericity visualization of defects gathered from micro-CT results using software for Ti6Al4V AM250 and M290 annealed specimens; b aspect ratio (AR) and circularity visualization of defects observed during optical microscopy [53]

Fig. 15 a Four identified pore groups; b pore number fraction for the four pore groups [54]

Fig. 16 Results from a high porosity SS316L specimen. a 3D rendering of the segmented void distribution for high-porosity AM SS sample before mechanical testing (left) and just before catastrophic failure (right); b tomographic images at different load and displacements during tensile loading [59]

Fig. 17 a XCT view of the broken tensile sample along the x-axis; b dual-view of the broken tensile sample with the fracture surface at the top part and the 3D void distribution at the bottom part. c, d: Two different views of two slices of the fracture surface and the projection of voids on the (XY) plane [61]

Fig. 18 Snapshots from 3D microtomography reconstructions: a-g crack propagation corresponding to the seven tomography scans; h crack elevation at various locations [63]

Fig. 19. Three-dimensional reconstruction results of the crack and the fracture morphology of in situ fatigue specimen. a 3D XCT of fracture schematic; b 3D rendering of defects and crack propagation after 1850 cycle; c the fatigue fracture morphology of the specimen at the maximum stress of 1175 MPa; d the result of 3D drawing is projected along the direction of principal stress, with yellow representing the crack, blue representing the defect, and red representing the crack surface defect [65]

Fig. 20 Time-series radiographs acquired during AM of an Invar 36 single-layer melt track under P?=?209 W, V?=?13 mm s-1 and LED?=?16.1 J mm-1.[68]

Fig. 21 Dynamic X-ray images of laser powder bed fusion processes of Ti6Al4V. The laser powers are 520 W. The laser beam size is?~?220 µm (1/e2). The powder particle size is in the range of 5-45 µm, and the powder layer thickness is?~?100 µm. The numbers indicate the time nodes. The laser is turned ON at t?=?0, and continues to heat the sample till t?=?1000 µs. The raw data were taken with a frame rate of 50 kHz. The exposure time for each individual image is 350 ns. All the scale bars are 200 µm [73]

Fig. 22 X-ray images of the melt pool, keyhole and porosity in a 4140 baseplate. a Fill; b high-energy (HE); c keyhole [80]

Fig. 23 Dynamic X-ray images showing powder motion at different moments and under different environmental pressures [84]

Fig. 24 Residual stress formation model: a heating-phase; b cooling phase. [95]

Fig. 25 XRD and hole-drilling principal stress measurements performed on the top surface of deposits with various build heights [99]

Fig. 26 a Schematic representation of the regions probed during the in situ XRD experiments; b room temperature X-ray diffraction patterns; c diffraction pattern of the HAZ at 150 °C [100]