Fig. 1. Schematic of steel/Al laser welding

Fig. 2. Macroscopic morphology of steel/Al weld surface. (a) Without Ti powder; (b) with Ti powder

Fig. 3. Microstructures of steel/Al joint. (a) Without Ti powder; (b) with Ti powder

Fig. 4. Elements distributions of steel/Al joint. (a) Al distribution without Ti powder; (b) Al distribution with Ti powder; (c) Ti distribution with Ti powder

Fig. 5. Grain size and distribution in weld zone of steel/Al joint. (a) Without Ti powder; (b) with Ti powder

Fig. 6. Element characteristic spectral line. (a) Without Ti powder; (b) with Ti powder

Fig. 7. Elements characteristics spectral lines in the band of 370‒410 nm. (a) Without Ti powder; (b) with Ti powder

Fig. 8. Spectral line fitting results with and without Ti powder

Fig. 9. Fracture positions of shear specimen of steel/Al joint. (a) Without Ti powder; (b) with Ti powder

Fig. 10. Fracture morphologies of shear specimen of steel/Al joint. (a) Without Ti powder; (b) with Ti powder

Fig. 11. EDS analysis of different positions of steel/Al joint. (a) (d) Scanning positions with and without Ti powder; (b) (e) scanning line Ⅰ; (c) (f) scanning line Ⅱ

Fig. 12. SEM images of interface layer of steel/Al joint. (a) (c) Without powder; (b) enlarged view of area Q1; (d) enlarged view of area Q2

Fig. 13. XRD spectra of steel/Al joint. (a) Without Ti powder; (b) with Ti powder