Fig. 1. Microstructure control of Al-based nano/in-situ composite processed by laser additive manufacturing. (a) Ring-structured TiC reinforcing phase^[37]; (b) strip-structured in-situ Al₄SiC₄ reinforcing phase^[42]; (c) fine equiaxed structure of Al-matrix with TiB₂ reinforcement^[43]

Fig. 2. Selective laser melting (SLM) additive manufacturing of 7075 aluminum alloy: transformation of columnar dendrites to fine equiaxed crystals and attendant crack suppression via nano-particle modification^[36]

Fig. 3. Comparison of microstructures between TC4 alloy and Ti-8.5Cu alloy processed by laser additive manufacturing^[67]. (a) TC4 alloy showing coarse columnar grain structure; (b) Ti-8.5Cu alloy showing fine and fully equiaxed grain structure

Fig. 4. Microstructure control of TC4 alloy processed by laser additive manufacturing combined with high-intensity ultrasound ^[69]. (a) Schematic of laser melting deposition process combined with high-intensity ultrasound; (b) conventional laser melting deposition TC4 alloy showing large columnar grains; (c) ultrasound combined laser additive manufacturing TC4 alloy showing fine equiaxed grains

Fig. 5. Mechanisms for metallurgical modification by nanoparticles during laser melting of Ni-based composites^[95]

Fig. 6. Microstructure and property control of laser additive manufacturing of Ni-based gradient interface composites and nanoparticle reinforced composites. (a) Gradient interface of micron-WC reinforced composites^[96]; (b) cellular structure of nano-TiC reinforced composites^[101]; (c) superhydrophobic surface of Ni-based nanocomposites^[102]

Fig. 7. LMD additive manufacturing of large-scale integral metal components^[104]. (a) Large-scale load-bearing titanium alloy components for aircrafts; (b) titanium alloy integral disk with gradient performance for aeroengine; (c) solidified grain structures in gradient transition zone between disk and blades

Fig. 8. Laser melting deposition and selective laser melting additive manufacturing of large-scale complex-shaped metal components. (a) LMD forming C919 titanium alloy rib edge strip with length of 3100 mm; (b) SLM forming titanium alloy fan blade edge wrapping with length of 1200 mm; (c) SLM forming nickel-based superalloy engine casing with size of Ф 576 mm×200 mm

Fig. 9. Selective laser melting manufactured copper alloy integral components and performance tests at NASA. (a) Hot-fire test of laser additive manufactured component conducted by NASA and Aerojet Rocketdyne^[106]; (b) integral components of copper alloy liner in combustion chamber of rocket engine^[107]

Fig. 10. Fuel nozzle components in aeroengine manufactured by General Electric Company using selective laser melting technology^[110]. (a) Advanced turboprop engine (ATP); (b) working principle of fuel nozzles in aeroengine; (c) laser additive manufactured fuel nozzle components

Fig. 11. Additive manufacturing of a designed lattice structure inspired by crystal microstructure based on hardening mechanism of metal crystal. (a) Lattice structure inspired by crystal microstructure; (b) difference of stress-strain curves between single-phase and multi-phase crystal lattice structures; (c) finite element method (FEM) simulation of stress distribution of lattice structure inspired by hexagonal close-packed (HCP) crystal ^[113]

Fig. 12. New bionic lattice cabin partition designed by Airbus and manufactured by selective laser melting technology^[115-117]. (a) Structure of bionic lattice cabin partition; (b) photograph of assembled bionic lattice cabin partition; (c) cross-scale structure design of bionic lattice cabin partition; (d) components of bionic partition processed by SLM additive manufacturing

Fig. 13. Laser additive manufacturing of lightweight and impact resistant bionic functional structures^[122,125]. (a) Macroscopic feature of mantis shrimp telson; (b) SLM process of bio-inspired bi-directionally corrugated panel impact resistant structure; (c) effect of height and wavelength of bi-directionally corrugated panel on crush force efficiency (CFE); (d) diving bell of water spider; (e) bionic reticulated