J. Cao et al Materials and Design 32(2011)2763-2770 and S304H HAZ are lower than that of their base materials respec- ively, while average impact strength value of T92 FGHAZ is higher than that of t9 2 base material Fig. 13 shows the impact fractograph of the joints. The fracture surfaces of t92 base material and t92 FGHaZ. as well as S304H base material exhibit ductile fracture characteristic and consist of fiber zone and radiation zone, especially the fiber zone occupys a big proportion. Beside these, there are a large number of small- sized dimples with different sizes and depths on their fracture su faces, which displays excellent plasticity of them. As for the S304H HAZ and t92 CGhaz, their fracture modes both belong to quasi- cleavage fracture. Compared with the fracture surfaces of two base materials, a larger brittle area is seen on their fracture surfaces. Thus, it can be inferred that the toughness of two base materials is better than that of two hazs. furthermore the amount of tear ridge around dimple in Fig. 13d is much more than that in Fig. 13e, indicating that the toughness of T92 CGHAZ is weaker BM FGHAZ CGHAZ WM S304H S304H than that of s304H haz in addition it can be seen from the frac- Fig. 12. Impact test results of T92/S304H dissimilar materials joints. ture surfaces of two base materials and their hazs that there are some precipitates in the dimples. For T92 base material and it's (b) (d) ( Fig. 13. SEM fractographs of (a)T92 base material, (b)92 FGHAZ (c)S304H base material, (d)S304H HAZ, (e)T92 CGHAZ, and( O weld metal.and S304H HAZ are lower than that of their base materials respec￾tively, while average impact strength value of T92 FGHAZ is higher than that of T92 base material. Fig. 13 shows the impact fractograph of the joints. The fracture surfaces of T92 base material and T92 FGHAZ, as well as S304H base material exhibit ductile fracture characteristic and consist of fiber zone and radiation zone, especially the fiber zone occupys a big proportion. Beside these, there are a large number of small￾sized dimples with different sizes and depths on their fracture sur￾faces, which displays excellent plasticity of them. As for the S304H HAZ and T92 CGHAZ, their fracture modes both belong to quasi￾cleavage fracture. Compared with the fracture surfaces of two base materials, a larger brittle area is seen on their fracture surfaces. Thus, it can be inferred that the toughness of two base materials is better than that of two HAZs. Furthermore, the amount of tear ridge around dimple in Fig. 13d is much more than that in Fig. 13e, indicating that the toughness of T92 CGHAZ is weaker than that of S304H HAZ. In addition, it can be seen from the frac￾ture surfaces of two base materials and their HAZs that there are some precipitates in the dimples. For T92 base material and it’s Fig. 12. Impact test results of T92/S304H dissimilar materials joints. Fig. 13. SEM fractographs of (a) T92 base material, (b) T92 FGHAZ, (c) S304H base material, (d) S304H HAZ, (e) T92 CGHAZ, and (f) weld metal. 2768 J. Cao et al. / Materials and Design 32 (2011) 2763–2770