Fig. 1. Time-series radiographs acquired during laser additive manufacturing (LAM) of Invar 36 single layer melt track. The effect of recoil pressure on metal powder movement and trajectory of pores under Marangoni convection were discovered^[25]

Fig. 2. Controlling instability during metal additive manufacturing^[47]. (a) X-ray images showing liquid breakup during laser melting of Al6061, where the broken liquid is indicated by dashed circle; (b) X-ray images showing laser melting of Al6061＋4.4% TiC, the pressure in liquid is stable and the liquid will not break; (c) vapor depression depth and width evolution with time during laser melting

Fig. 3. Time-lapse images of samples at different numbers of cycles^[113], where the first, second, and third rows show three-dimensional images of voids, virtual slice at neckdown position, and longitudinal section. (a) AlSi10Mg sample (HT105) tested at 250 ℃ and peak load of 105 MPa; (b) AlSi10Mg sample (RT260) tested at room temperature and peak load of 260 MPa

Fig. 4. Von Mises residual stress (RS) at the top of sample in thin-baseplate (TB) condition^[117]

Fig. 5. Measurement of residual stress in metal components prepared by additive manufacturing. (a) Distribution of measurement points on the sample for neutron diffraction residual stress measurement^[89]; (b) schematic of KOWARI neutron diffraction device for residual stress measurement in experiment^[89]; (c) schematic of in-situ neutron diffraction experiment for measuring lattice strain^[92]

Fig. 6. Evolution and analysis of solid-state phase transformation of additive manufacturing metal components. (a) Evolution of measured and calculated volume fraction of γ′ phase during thermal cycling^[125]; (b) relationship between martensite phase volume fraction of tensile sample and true strain^[82]

Fig. 7. Evolution of total dislocation density at three representative axial positions versus true strain^[129] (RD: parallel to sonotrode rolling direction; TD: parallel to sonotrode vibration direction)