Fig. 1. Comparison of Gaussian and flat-top laser additive manufacturing technology. (a) Schematic diagram of beam shaping^[58]; (b) energy distribution and temperature field of melt pool^[59-60]; (c) schematic diagram of interaction with powder^[68]; (d) OM diagram of AlSi10Mg alloy^[68]; (e) SEM image of Ti-Nb alloy^[70]; (f) EBSD image of IN718 alloy^[76]

Fig. 2. Comparison of Gaussian and anti-Gaussian laser additive manufacturing technology. (a) Shaping principle and two-dimensional energy distribution diagram^[78]; (b) SEM image of IN738LC alloy^[78]; (c) three-dimensional energy distribution diagram, temperature distribution of melt pool and single-track morphology^[80]

Fig. 3. Comparison of Gaussian and Bessel laser additive manufacturing technology. (a) Schematic diagram of beam shaping, energy distribution and depth-to-width ratio of melt pool; (b) morphology of formed melt pool; (c) EBSD image of prepared 316L alloy^[84]

Fig. 4. Comparison of Gaussian and elliptical laser additive manufacturing technology. (a) Spot energy distribution diagram^[85]; (b) thermodynamic simulation of melt track X-Y, X-Z and Y-Z plane observations (modes with principal axis of elliptical beam parallel and perpendicular to scanning direction are denoted by LE and TE, respectively)^[85,87]; (c) SEM image at melt pool bottom of 316L alloy^[85]; (d) EBSD image of side of 316L alloy^[86]

Fig. 5. Comparison of additive manufacturing technology between focusing laser and defocusing laser. (a) Schematic diagram of defocusing laser^[88]; (b) OM diagrams of IN718 alloy with defocus of 0, 5, 10, 15 and 20 mm, respectively^[88]; (c) OM diagram of AlSi10Mg alloy ^[91]; (d) SEM and EBSD images of side of IN718 alloy^[92]

Fig. 6. Substrate preheating assisted laser additive manufacturing technology. (a) OM diagrams of TiAl alloy preheating at 600, 800, 900 ℃^[97]; (b) 316L microstructure without preheating and with preheating at 150 ℃^[101]; (c) temperature distribution of FeCoMo alloy fabricated at 500 ℃ preheating^[106]; (d) EBSD images of TiAl alloy at preheating temperature of 25, 150, 250, 350 ℃^[112]; (e) loading-unloading curves and nano-hardness values of TiAl alloy at different preheating temperatures^[112]

Fig. 7. Electromagnetic induction heating assisted laser additive manufacturing technology. (a) Comparison of schematic diagram of laser scanning preheating, resistance wire preheating and electromagnetic induction heating^[114]; (b) photos of electromagnetic induction heating process and microstructure of TiAl alloy without preheating and with preheating at 800 ℃^[114]; (c) schematic diagram of electromagnetic induction-assisted LDED^[115]

Fig. 8. Laser scanning preheating assisted laser additive manufacturing technology. (a) Laser synchronous preheating in LDED process^[121]; (b) microstructure of 60%IN625-40%Ti6Al4V composites with and without preheating^[120]; (c) photos of prepared samples with and without preheating^[119]; (d) diagram of laser scanning assisted SLM process^[123]

Fig. 9. Static magnetic field assisted laser additive manufacturing technology. (a) Schematic diagram of static magnetic field-assisted SLM and field intensity distribution^[133]; (b) 3D simulation results of thermal electromagnetic force acting on dendrites in 0.12 T static magnetic field^[133]; (c) EBSD image of AlSi10Mg alloy prepared by SLM with 0.85 mT and without static magnetic field^[130]; (d) schematic diagram of thermal electromagnetic force-induced dendrite breakage^[17]; (e) tensile stress-strain curves and mechanical properties of AlSi10Mg prepared by SLM with the assistance of 0, 0.1, 0.2 and 0.3 T magnetic fields^[17]

Fig. 10. Alternating magnetic field assisted laser additive manufacturing technology. (a) Schematic diagram of alternating magnetic field-assisted SLM^[143]; (b) EBSD image of 316L alloy prepared under 0.4 mT, 300 Hz alternating magnetic field and no magnetic field^[143]; (c) solidification behavior of melt pool in synchronous electromagnetic induction-assisted LDED process^[144]; (d) micro-morphology of TiC enhanced Ti6Al4V alloy with and without high-frequency electromagnetic field^[144]

Fig. 11. Ultrasonic vibration-assisted laser additive manufacturing technology. (a) Solidification behavior of melt pool in ultrasonic assisted LDED^[151]; (b) micro-morphology of IN718 prepared by LDED at different ultrasonic frequencies (0, 25, 33, 41 kHz)^[153]; (c) EBSD image of 316L alloy prepared by LDED with 20 kHz and without ultrasonic field^[154]; (d) OM diagram of 316L stainless steel fabricated by LDED with and without ultrasonic field assistance^[156]

Fig. 12. Ultrasonic impact-assisted laser additive manufacturing technology. (a) Scan strategy^[159]; (b) microscope images of LDED-fabricated IN100 superalloy with and without 75 N ultrasonic impact^[159]; (c) inverse pole figure (IPF) mappings, kernel average misorientation (KAM), and grain boundary (GB) distribution of LDED-fabricated IN718 with and without ultrasonic impact^[165]