Fig. 1. Principle of inside-laser powder feeding

Fig. 2. Three parts of designed model. (a) The first part; (b) the second part; (c) the third part

Fig. 3. Layering method of twisted structure. (a) Layering according to twisted shape; (b) scanning direction; (c) dissociation along scanning direction; (d) discrete units

Fig. 4. Forming track of twisted structure. (a) Coordinate transformation process; (b) cross section of the third part

Fig. 5. Powder distribution state under different deflection angles. (a) 0°;(b) 30°;(c) 60°;(d) 90°

Fig. 6. Forming process of multivariant twisted structure

Fig. 7. Formed twisted structure. (a) Height of formed part; (b) thickness of formed part; (c) width of formed part; (d) rotation angle of the first part; (e) torsion angle of the first part; (f) center angle of the front end face of the third part; (g) center angle of the rear face of the third part; (h) side of the forming part

Fig. 8. Micro-hardness measurement. (a) Schematic of sampling positions for measurement; (b) micro-hardness at different locations

Fig. 9. Three-dimensional topographies of the surfaces on A and B sides of each part. (a) A side of the first part; (b) B side of the first part; (c) A side of the second part; (d) B side of the second part; (e) A side of the third part; (f) B side of the third part

Fig. 10. Microstructures at different positions of formed part. (a) Position 1; (b) position 2; (c) position 3