*2.1. Materials*

Four different materials (A508, 52Mb, 52Mw and 316L) selected from a dissimilar metal-welded joint (DMWJ) in nuclear power plant were used in this study, as shown in Figure 1. The DMWJ was fabricated by Shanghai Company of Nuclear Power Equipment (Shanghai, China). The DMWJ was a full scale mock up of the DMWJ in a nuclear power plants. During the manufacturing process, the base metal A508 was pre-heated to 125 ◦C before buttering to prevent weld cracking. The buttering layer was deposited using a 1.2 mm diameter Alloy52M welding wire using automatic gas-tungsten arc welding (GTAW) on the ferritic nozzle face. The welding current, voltage and speed were 200 A, 11.5 V and 1.85 mm/s, respectively. A total of 478 weld passes were deposited, and the buttering layer with an average width of 20 mm was formed. Then, heat treatment (annealing at 610 ◦C for 15 h, with subsequent furnace cooling to 300 ◦C) was conducted on the buttering to relieve the residual stress. Thereafter, 100% non-destructive testing was performed on the buttering. This buttering layer material is denoted as buttering 52Mb.

**Figure 1.** A dissimilar metal welded joint in a nuclear power plant.

After buttering, welding was carried out between the buttering layer and the austenitic safe-end pipe using GTAW and a 0.9 mm diameter Alloy52M welding wire. The welding current, voltage and speed were 180 A, 10 V and 1.75 mm/s, respectively. A total of 439 weld passes were deposited, and the weld with an average width of 19 mm was formed. After welding, 100% nondestructive testing was performed again on the weld. This weld metal material is denoted as weld 52Mw.

The true stress-strain curves of the four different materials at room temperature have been obtained [22], as shown in Figure 2. The measured Young's modulus *E* of A508, 52Mb, 52Mw and 316L are 202,410 MPa, 178,130 MPa, 178,130 MPa and 156,150 MPa, respectively, and the Poisson's ratios *ν* of them are 0.3 [22].

**Figure 2.** The true stress-strain curves of four materials. Reprinted from Materials Science and Engineering A, 568, Wang, H.T.; Wang, G.Z.; Xuan, F.Z.; Liu, C.J.; Tu, S.T.; Local mechanical properties of a dissimilar metal welded joint in nuclear power systems, 108, Copyright 2013, with permission from Elsevier. [22].
