Fig. 1. Microstructure of materials. (a) DP980; (b) 22MnB5

Fig. 2. Schematic of tensile specimen

Fig. 3. Schematic of hardness points on cross section of welded joint

Fig. 4. Fracture position of tensile specimen

Fig. 5. SEM morphology of tensile specimen fracture

Fig. 6. Cross-sectional macro-morphology of welded joint and its regional division

Fig. 7. Morphologies of welded joint in different zones. (a) Tempered zone of DP980(zone a in Fig. 6); (b) two-phase zone of DP980 (zone b in Fig. 6); (c) fine-grain zone of DP980 (zone c in Fig. 6); (d) coarse-grain zone of DP980 (zone d in Fig. 6); (e) fusion zone of DP980(zone e in Fig. 6); (f) weld metal (zone f in Fig. 6); (g) coarse-grain zone of 22MnB5 (zone g in Fig. 6); (h) fine-grain zone of 22MnB5 (zone h in Fig. 6); (i) fusion zone of 22MnB5 (zone i in Fig. 6); (j) two-phase zone of 22MnB5 (

Fig. 8. Cross-sectional hardness distribution of welded joint

Table 1. Chemical compositions of DP980 and 22MnB5(mass fraction, %)

Table 2. Mechanical properties of DP980 and 22MnB5

Table 3. Mechanical properties of welded joints