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As the core component of China Fusion Engineering Test Reactor (CFETR), the forming and manufacturing of the first wall faces severe challenges due to the constraints of materials, service environment and geometric structure. The microstructure and mechanical properties of welded joints obtained by rolled and laser selective melted (SLMed) reduced activation ferritic/martensitic (RAFM) steel were investigated in depth. The microstructure analysis results showed that the weld metal (WM) was composed of coarse lath martensite and δ-ferrite, while the microstructure were mainly coarse grains in heat affected zone (HAZ) which was easy to break. The average grains size of SLMed RAFM steel (S-RAFMs) was smaller than that of rolled RAFM steel (R-RAFMs), since the rapid melting and solidification of laser in the additive manufacturing process prevented grains to grow. The microstructure of R-RAFMs joint was relatively more uniform and there was no obvious texture and preferred orientation, while the WM of S-RAFMs joint had a weak cubic texture. The results of mechanical properties showed that the S-RAFMs joints exhibited higher strength (UTS = 697.46 MPa) and the R-RAFMs joints exhibited better plasticity (EL = 13.49 %) under the same tensile conditions. The tensile and impact fracture morphologies showed that the fracture mechanism of two joints was ductile-brittle mixed fracture, and the dimples of R-RAFMs joints were finer and denser. It was clearly observed that the hardness of WM (∼390–430 HV0.3) was higher than that of the base metal (BM) (∼190–230 HV0.3) from the hardness distributions along the width directions. The average hardness of BM in R-RAFMs joint (227 HV0.3) was lower than S-RAFMs joint (197.3 HV0.3), which was mainly related to the fine grain strengthening effect during SLM forming. The above results may provide theoretical guidance for the high-performance manufacturing of the first wall and promote the application of SLM and EBW technology in the field of nuclear fusion.

The CFETR is the next generation magnetic confinement tokamak, its increasing heating needs and stringent shielding requirements present new challenges for the ECRH launcher. In an effort to evaluate the viability of the equatorial launcher, a port plug prototype is designed and its performance under steady state or some interrupted events is assessed. The well-configured steel/water ratio is beneficial to improve its shielding capability and effectively mitigate the 493 kW heat. The maximum temperature of the port plug is less than 300 °C when the inlet temperature is 70 °C, and the average outlet water temperature reaches 142 °C. The worst EM case is a major disruption of the plasma, which would induce about 200 kN force on the port plug at the end of the plasma current linear decay. The combined heat and EM force loads on the port plug would result in a total deformation of 1.7 mm and a maximum equivalent stress of 320 MPa, with little impacts on the port plug or the surrounding vacuum vessel. As the installation of the port plug, the H and He generation rates of the surrounding vacuum vessel have increased by about 2 % and 1 % separately, but remain lower than the limit of 1 appm/FPY, and the nuclear heat density of the toroidal field coils has increased by about 5%.

5A06 aluminum alloy bar was brazed by temperature gradient transient liquid phase diffusion welding (TG-TLP). The effects of brazing temperature on the microstructure and the tensile strength of the brazing joints were investigated. Three typical brazing filler alloys (1# Al-20Cu-6Si-2Ni, 2# Al-10Cu-10Si-3Mg-1Ga, and 3# Al-6Cu-10Si-2Mg-10Zn) were prepared by smelting, and TG-TLP diffusion bonding was carried out at different brazing temperatures (550 °C~590 °C). The results show that with the increase in brazing temperature, the oxide films at the brazing junction are easier to be broken and dispersed, but the oxidation extent will also increase. The oxidation products enriched were mainly Al2O3 and SiO2 at the brazing junction. There are different optimal brazing temperatures corresponding to the different filler alloys. For 1#, the optimal temperature is 570 °C; for 2# is 580 °C; for 3# is 580 °C. For 1# brazing joints, the maximum tensile strength was 113 MPa, and for 2# was 122.4 MPa. Under the experimental conditions of this study, the maximum tensile strength of the TG-TLP joint is 147.4 MPa of 3# brazing sample (at 580 °C), which has increased by 30% and 20% compared to 1# and 2# respectively. The nickel-rich phase at the interface (of 1# brazing filler) could form a brittle fracture, which was unfavorable for interface bonding. For TG-TLP brazing of 5A06, the filler alloy with high Al:Cu ratio (12:1 wt.%) needs a sufficient temperature gradient to exert the film-breaking effect, while the filler alloy with low Al:Cu ratio (3.6:1 wt.%) needs to accurately control its brazing temperature to avoid excessive oxidation. There are many research gaps in the influence of brazing material composition and brazing temperature on the microstructure and mechanical properties of 5A06 aluminum alloy TG-TLP joints. The research results can provide a theoretical basis for formulating the TG-TLP brazing specification of 5A06 aluminum alloy.