Fig. 1. Schematic diagram of laser processing

Fig. 2. XRD patterns of samples in different states before and after tensile test

Fig. 3. Common and color metallographic microstructure of samples in different states. (a)(b) Laser deposition; (c)(d) 280 ℃ preheating; (e)(f) 320 ℃ preheating

Fig. 4. SEM microstructure of samples in different states. (a)(b) Laser deposition; (c)(d) 280 ℃ preheating; (e)(f) 320 ℃ preheating

Fig. 5. IPF maps of samples in different states and distribution of packet sizes. (a) IPF diagram of laser deposited sample; (b) IPF diagram of 280 ℃ preheating sample; (c) IPF diagram of 320 ℃ preheating sample; (d) distribution of packet sizes

Fig. 6. EBSD BC maps and BC value distribution of samples with different preheating temperatures. (a) BC map of sample preheated at 280 ℃; (b) BC value distribution of sample preheated at 280 ℃; (c) BC map of sample preheated at 320 ℃; (d) BC value distribution of sample preheated at 320 ℃

Fig. 7. Distribution of bainite and martensite in samples with different preheating temperatures. (a) 280 ℃ preheating; (b) 320 ℃ preheating

Fig. 8. Distribution results of samples with different preheating temperatures. (a) Distribution map of high-angle grain boundary for sample preheated at 280 ℃; (b) statistical distribution of grain boundary misorientation for sample preheated at 280 ℃; (c) distribution map of low-angle grain boundary for sample preheated at 320 ℃; (d) statistical distribution of grain boundary misorientation for sample preheated at 320 ℃

Fig. 9. Tensile properties of samples in different states. (a) Engineering stress-strain curves; (b) tensile properties; (c) comparison of product of strength and elongation of laser deposited high strength steels

Fig. 10. Fracture surface morphology of samples in different states. (a) Laser deposition; (b) 280 ℃ preheating; (c) 320 ℃ preheating

Fig. 11. Transformation law of undercooled austenite in experimental steel and temperature history of laser deposition. (a) TTT curves; (b) schematic diagram of samples’ temperature changing over time