Fig. 1. CT sample. (a) Location; (b) sample size; (c) weld surface

Fig. 2. Fatigue crack growth rate of micro area sample

Fig. 3. Microstructures of microcells. (a) BM; (b) ADZ; (c) LDZ; (d) CGHAZ; (e) FGHAZ;(f) non-full phase transformation area

Fig. 4. Path of fatigue crack propagation. (a) ADZ; (b) LDZ; (c) HAZ

Fig. 5. Fatigue crack propagation path of weld area. (a) Lower ΔK area of ADZ; (b) higher ΔK area of ADZ; (c) lower ΔK area of LDZ; (d) higher ΔK area of LDZ

Fig. 6. Fatigue crack propagation path of HAZ. (a) Starting crack position; (b) lower ΔK area; (c) deflection position 1; (d) deflection position 2

Fig. 7. Fracture morphology of each microcell when da/dN=1×10-4 mm·cycle-1. (a) Base metal; (b) local amplification of base metal; (c) ADZ; (d) local amplification of ADZ; (e) LDZ; (f) local amplification of LDZ; (g) HAZ; (h) local amplification of HAZ

Fig. 8. Fracture morphology of each microcell when ΔK=80 MPa·m12. (a) Base metal; (b) local amplification of base metal;(c) ADZ; (d) local amplification of ADZ; (e) LDZ; (f) local amplification of LDZ; (g) HAZ; (h) local amplification of HAZ